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The importance of soluble microbial products (SMPs) in biological drinking water treatment

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Abstract

The formation of soluble microbial products (SMPs) during a drinking water ozone-biofiltration process was estimated using two approaches. First, a model was developed that related the assimilation of biodegradable organic matter (BOM) to the accumulation of biomass on filter media. The model was calibrated with data from a regularly backwashed, pilot scale biofilter that approximated a steady-state plug flow reactor. The second approach was a direct measurement of SMP concentrations, accomplished by applying a synthetic water comprised of known compounds to a bio-acclimated filter. The SMP concentration was estimated by determining the difference between known-compound removal (on a carbon basis) and dissolved organic carbon (DOC) removal, Comparable results were obtained from both approaches. SMPs were found to be important relative to the carbon removal that is typically measured (DOC), indicating that this measurement can significantly underestimate the actual BOM removal (17-33% in this research). The concentration of SMPs was negligible relative to the filter effluent DOC pool.

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... When ozone dosing was suddenly terminated , a portion of the microorganisms in the BAC may have shifted from exogenous respiration to endogenous respiration due to the reduction in biodegradable organic matter (Yapsakli et al., 2010), which is likely to have resulted in the release of numerous soluble microbial products (SMPs) (Schiener et al., 1998 ). It is known that a range of SMPs are produced by microorganisms in the BAC process and can be detected in BAC effluent (Barker and Stuckey, 1999; Carlson and Amy, 2000; Kunacheva and Stuckey, 2014). SMPs comprise a wide range of high and lowFig. ...
... molecular weight compounds including many DON compounds such as proteins, polysaccharide and amino acids (Rittmann et al., 1987; Chen et al., 2003; Potvin and Zhou, 2011), which can be divided into growth-related utilization associated products (UAPs) and non-growth-related biomass associated products (BAPs). The formation of UAPs and BAPs is directly related to the cell growth rate and the cell endogenous respiration of the microorganisms , respectively (Carlson and Amy, 2000). As shown inFig. ...
... Woolschlager and Rittmann (1995a) modelled the formation of UAPs and BAPs in a batch bioreactor and showed that the presence of SMP can cause the BOM concentration to be underestimated by 30 ± 40% when DOC removal is used to estimate BOM. Following similar modelling principles, Carlson and Amy (2000) showed that the SMP and EPS can increase the effluent DOC masking the removal by BAC and underestimate BOM removal by 17e33% in an ozonated water when biofilter with anthracite medium was used (Fig. 6). It could be noted the amount of BOM in the ozonated water of these authors is only 20% and the removal is 10e15% as opposed to that of 65% at the end of 'period C' with the BAC. ...
... Therefore, this affects the quality of effluent and total organic removal in subsequent physicochemical processes. The formation of SMP is related to the BOM removal and the biomass concentration (Carlson and Amy, 2000). The SMP contained mainly high MW organic compounds (Namkung and Rittmann, 1986). ...
... Mostly, BAC is used (i.e. in odour control) as a post-treatment to the coagulation and rarely, as a pre-treatment for enhanced DOC removal or to improve the coagulability of organic matters (Aryal et al., 2011). Generally, the BAC is known to reduce assimilable organic matter, however, the SMP that could be present in the BAC effluent is been neglected without considering its impact on effluent quality (Carlson and Amy, 2000). Mainly, two issues can be identified for the limited application of BAC in the water treatment industry. ...
Article
This study shows if biologically activated carbon (BAC) is backwashed at the correct frequency, a number of benefits can be derived in addition to aiding the subsequent coagulation process. Previous studies have shown that the BAC improves the removal of dissolved organic carbon (DOC) by subsequent coagulation by decreasing non-coagulable dissolved organic carbon (NC-DOC). However, the actual mechanism of such observation or optimising strategies of NC-DOC removal is unknown. The impact of backwashing on BAC reactor performance in terms of NC-DOC removal and microbial community structure was investigated. A laboratory scale BAC column was operated for more than five months with backwashing at once every five days, but in one cycle it was operated without backwashing for 14 days and the effluent collected at different times from the last backwash was subjected to enhanced coagulation (EC). All the effluent of BAC collected at different days depicted better floc forming characteristics than the feed water which is raw surface water. The effluent collected on day 3 from the last backwash (BAC-3d) contained the least amount (1.64 mg/L) of NC-DOC despite the highest DOC (3.89 mg/L) of all effluents. The coagulant requirement (5 mg-Fe³⁺/mg-DOC) was minimal for BAC-3d effluent among raw water and all other BAC effluent water samples. This is remarkable given the raw water contained 2.76 mg/L of NC-DOC. The microbial community on BAC granules on day 3 contained a higher abundance of biodegradable organic matter (BOM) removing microorganisms and low abundance of opportunistic pathogens. Similar performance in terms of DOC removal with the backwash was also observed in the continuous operation of other BAC columns. Possible backwash frequency that optimises the BAC/EC and derives many other benefits is proposed. The BAC/EC combination could help solve many emerging issues cost-effectively hence, needs further investigation and cost-benefit analysis.
... Evidence that toxicity can be generated in biological systems (Eckenfelder, 1995) raises concern when considering the adoption of biological systems for post-treatment and the reuse of treated wastewaters. Moreover, the employment of biofilms as part of water treatment processes may lead to the release of compounds that may act as precursors of disinfection by-products when chlorine is applied as the primary disinfectant (Carlson and Amy, 2000). ...
Article
The residual COD from anaerobic treatment processes is usually too high to comply with legislative discharge levels. It has been shown that in well operated systems the majority of the effluent COD originates from soluble microbial products (SMP) produced by the system itself, hence the characteristics of these compounds become important when assessing post-treatment systems to remove the residual COD. The molecular weight (MW) distribution and the identification of SMP in the effluents from three different anaerobic reactors will be presented. It has been found that the bulk of SMP lies in the low MW range, though compounds with MW as high as 300 kDa were also present in all anaerobic effluents. Preliminary results on the identification of such compounds using GC/MS surprisingly revealed the presence of long chain alkenes (C12-C24) and alkanes (C12-C16), as well as some aromatic compounds. These compounds that likely come from cell lysis and endogenous decay may not be easily biodegradable, hence their presence in the effluent is likely to cause the residual COD.
... Rittmann et al. (1987) described SMPs as being relatively high in molecular weight (usually greater than the original substrate), having a high degree of aromaticity, and possessing slow bio-reaction kinetics. Data from biological filters indicated that SMPs increased with filter depth; however, the amount of SMPs in the filter effluent was relatively minor in comparison to the pool of dissolved organic carbon (Carlson et al., 1996). Based on the overall effluent BOM shown in Fig. 3, the portion of SMPs is proportionally lower than the effluent NPOC concentration (greater than 1000 mg C/m 3 ). ...
Article
This paper evaluates the rate of utilization of easily biodegradable organic compounds by drinking water biofilms. Tap water, which had been filtered through biologically active granular activated carbon, was used as an innoculum for biofilm growth in annular reactors (ARs). Synthetic cocktails of easily biodegradable material in the concentration range of 50-2,000 mgC/m3 were used as substrate for biofilm growth. Influent and effluent aggregate concentrations of biodegradable organic matter (BOM) were calculated by adding the measurable BOM components on a mass carbon basis. The aggregate BOM values were used for calculating the observed Damköhler number and Theile modulus (based on a reaction rate per unit surface area), which were used to determine whether external or internal mass transfer limited BOM removal. For all of the experimental trials, it was shown that neither external nor internal mass transfer limited BOM removal. Because the biofilms in this research are thin and the fact that mass transfer is not limiting, it was assumed that the bulk BOM concentration was approximately equal to the average BOM concentration in the biofilm. A linear model was obtained for the aggregate BOM flux and the product of the effluent BOM concentration and the biofilm density. The slope or the areal biodegradation rate (ka) for the aggregate BOM was 0.033 m/h, as determined through a linear regression.
... Decreased non-sorbable and increased sorbable DOC concentrations resulting from increased EBCT indicate the role of microbial activities in the BAC bed. This is in agreement with the previous studies that BAC is suspected to preferentially remove hydrophilic fraction and there is a possibility that soluble microbial products (SMPs) are released during the passage through BAC [22,23]. Those SMPs have been shown to be a larger molecular weight sorbable compound and preferably removed by coagulant [24]. ...
Article
Effluent organic matter (EfOM) in secondary wastewater effluent (SWWE) contains a wide range of organic compounds, which varies depending on wastewater treatment plant performance. Its removal is required for various reuse/recycling applications. Traditionally, enhanced coagulation (EC) process is followed by biological activated carbon (BAC), EC/BAC combination, in order to obtain additional dissolved organic carbon (DOC) removal. However, this study elucidates the effectiveness of BAC/EC combination by modelling DOC removal resulting from EC of SWWE and BAC effluent obtained at different empty bed contact time (EBCT). The result suggests that BAC reduces the coagulant non-sorbable DOC concentration significantly which otherwise remains unaffected by the traditional combination. Further, non-sorbable concentration decreased with increased EBCT. This clearly indicates the crucial role of biological activities on increasing the performance of coagulant.
... The characteristics of the mixed liquor are controlled by food to microorganism ratio (F/M) and wastewater composition, and may affect the membrane fouling [3] [4] [5] [6] [7] [8] [9] [10]. Activated sludge has many different components, such as extracellular polymeric substances (EPS), soluble microbial products (SMP) and colloids, which can interact with the membrane in different ways [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21]. As a result, some attempts have been made to modify the properties of the activated sludge, for example, by using biological powdered activated carbon sludge and granular sludge to control the fouling [22] [23]. ...
Article
Submerged membrane bioreactors (SMBRs) operate at constant imposed flux usually with the membranes in direct contact with the mixed liquor. Membrane fouling is evident as a rise in the required transmembrane pressure (TMP). In this paper we describe the rise in TMP as a three stage process. Stage 1 occurs in a period of a few hours and involves abrupt TMP rise due to ‘conditioning’, presumably by pore blockage and closure. Stage 2 is a prolonged period of slow TMP rise, which we ascribe to accumulation of extracellular polymeric substances (EPS) and other products of bioactivity, either deposited from the bulk liquor or produced in biofilms on the membrane surface. Polysaccharides are predominant in the supernatant EPS, and appear to be major membrane foulants deposited by the filtration process. Stage 3 is a sudden rise in TMP, which rapidly leads to inoperability of the membranes. This stage could have several causes, which we summarize, and which are all driven by the self-accelerating nature of fouling under constant flux operation.In order to understand the complex nature of fouling in submerged MBRs we have developed the MBR ‘roadmap’ that shows the relationship between the many operational and design characteristics of the MBR and the generic ‘fouling factors’, i.e. the nature of the feed (to the membrane), the membrane properties, and the hydrodynamic environment. We also present a MBR ‘fouling mechanism map’ which depicts the three stages of fouling and the multiple fouling mechanisms that could occur. Experimental observations are provided in support of many of the proposed fouling mechanisms.
... Microbial products have been shown to have higher molecular weights and be less biodegradable than the original soluble organic substrates (Carlson and Amy, 2000). In the simulations, it was assumed that only readily biodegradable organic substrates, inert soluble organic material and a fraction of microbial products pass through the membrane. ...
Article
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This paper proposes a modification of ASM3 in a way that takes into account the process of production and consumption of microbial products (MPs) in a submerged membrane bioreactor fed with the effluent of a particular precoagulation sedimentation unit. A comparative representation of the modeling results obtained with ASM3 and ASM1 is performed and it highlights the importance of considering the process of storage of organic substrate, including MPs, as a prior step to bacterial growth. In addition to the suspended solids and microorganisms, various soluble organic substances, which might be either undecomposed organic substances contained in the raw water or MPs, are assumed to be selectively retained within the bioreactor. The results show that the carbonaceous materials are more accurately estimated by ASM3, while ASM1 performs slightly better than ASM3 in the estimation of nitrate. The estimated MP concentration in the mixed liquor and permeate agrees with the experimental evidence, and as expected, MPs play a role in supplying organic substrate to heterotrophs in both ASM1 and ASM3.
... Definition of mineralization mass balances using DOC was not possible. BDOC is influenced by cell decay, the formation of metabolites and excretion of cellular components ͑Namkung and Rittman 1986; Kaplan and Newbold 1995;Carlson and Amy 2000;Quanrud et al. 2003͒. Thus the DOC measurement yields a net value, which underestimates the true biodegradation by as much as 32% ͑Kaplan and Newbold 1995͒. ...
Article
Artificial groundwater recharge for drinking water production involves infiltration of surface water through sandy soil and its capture into a groundwater aquifer. The transformation of aqueous organic matter is one of the central issues in this process. The purpose of this work was to assess the potential of indigenous microorganisms in the source water to contribute in the aqueous organic matter biodegradation. For this purpose, microorganisms were enriched from the source water in a fluidized-bed reactor (FBR) and used for kinetic studies on biodegradation of organic matter at ambient temperature range. Lake water (total organic carbon 5.8 mg L-1) was continuously fed to the FBR containing porous carrier material to support biomass retention. In the inlet and outlet water there were on average 21±6 and 13±5× 105 cells mL-1, respectively. Biofilm accumulation (as volatile solids) reached 13.1 mg g-1 dw carrier. In the continuous-flow mode and the batch tests, the highest oxygen consumption rate appeared in the summer, followed by the fall, spring, and winter. At low temperatures, the biodegradation of aqueous organic matter was relatively rapid initially for labile fractions followed by a slower phase for refractory fractions. The average temperature coefficient (Q10) in the system was 2.3 illustrating a strong temperature dependency of oxygen consumption. The isotopic analysis of dissolved inorganic carbon δ13 CDIC analysis revealed 27 and 69% mineralizations of dissolved organic carbon at 23 and 6°C over 65 and 630 min, respectively. These results can be used to construct additional input parameters in modeling applications of artificial groundwater recharge process. The biological component especially, i.e., the biodegradation, is difficult to predict for on-site applications without experimental proof and thus the interpretation in this study will help formulate design predictions for the process.
... Evidence that toxicity can be generated in biological systems (Eckenfelder, 1995) raises concern when considering the adoption of biological systems for post-treatment and the reuse of treated wastewaters. Moreover, the employment of biofilms as part of water treatment processes may lead to the release of compounds that may act as precursors of disinfection by-products when chlorine is applied as the primary disinfectant (Carlson and Amy, 2000). ...
Article
Anaerobic wastewater treatment processes cannot usually achieve discharge levels of COD without some form of post-treatment due to the high levels of soluble residual COD in the effluent. However, there is very little information in the literature on the nature of this material, and hence the aim of this work was to characterise effluents from several different anaerobic processes by their: molecular weight (MW) distributions (using the techniques of ultrafiltration and size exclusion chromatography); biodegradability (both aerobic and anaerobic) and activated carbon adsorption characteristics. The MW distribution data indicated that the majority (up to 89% w/w) of the material present in the effluents was in the low MW range (i.e. MW<1 kDa), although there was a significant amount (up to 22% w/w) in the high MW range (i.e. MW>300 kDa). Differences in the distributions were observed according to reactor type, with effluents from anaerobic baffled reactors (ABRs) containing a higher proportion of high MW material than effluents from other reactor types. Aerobic degradation of the effluents was significantly more successful than anaerobic, despite the fact that the low MW material was found to be the most difficult to degrade aerobically. Activated carbon adsorption revealed that the low MW material was more difficult to adsorb than the high MW compounds. The data was fitted to Freundlich, Langmuir and BET isotherms and it was concluded that the Freundlich model was the most accurate for predicting removal efficiencies especially with regard to scale up. Some generic patterns emerged with respect to the characterisation of the effluents and these will assist in decisions regarding post-treatment. Nevertheless, in order for these generic patterns to be confirmed more work is needed on characterising effluent samples from anaerobic treatments.
... Although the foulants consisting of proteins and polysaccharides may also originate from NOM in the feed water, it is believed that a large proportion of these substances could be derived from microorganisms in the bioreactor. First, proteins and polysaccharides are reported to be important metabolic products of bacteria in both water and wastewater treatment systems [27,28]. Second, the fouling rate of the MF/UF system was much lower than that of the PAC-MBR (Supplementary data Fig. ...
... In contrast to what is known about SMP formation in wastewater treatment, the research on SMP formation in drinking water treatment is very limited. Only a few related references can be found, of which the work by Carlson and Amy (2000) might be the most important. They investigated SMP with mathematical modeling and direct measurement and regarded SMP as an important factor in the underestimation of dissolved organic carbon (DOC) removal in biofiltration. ...
Article
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Both a theoretical and an empirical model were developed for predicting the formation of soluble microbial products (SMP) during drinking water biofiltration. Four pilot-scale biofilters with ceramsite as the medium were fed with different acetate loadings for the determination of SMP formation. Using numerically simulated and measured parameters, the theoretical model was developed according to the substrate and biomass balance. The results of this model matched the measured data better for higher SMP formation but did not fit well when SMP formation was lower. In order to better simulate the reality and overcome the difficulties of measuring the kinetic parameters, a simpler empirical model was also developed. In this model, SMP formation was expressed as a function of fed organic loadings and the depth of the medium, and a much better fit was obtained.
... Evidence that toxicity can be generated in biological systems (Eckenfelder, 1995) raises concern when considering the adoption of biological systems for post-treatment and the reuse of treated wastewaters. Moreover, the employment of biofilms as part of water treatment processes may lead to the release of compounds that may act as precursors of disinfection by-products when chlorine is applied as the primary disinfectant (Carlson and Amy, 2000). ...
Article
This paper presents results on the quantification and chromatographic characterization of soluble microbial products (SMP) accumulated in two laboratory-scale reactors: a submerged anaerobic membrane reactor (SAMBR or MBR), and an anaerobic CSTR. The results obtained under steady-state conditions show that 2.1% of the substrate was channelled into the production of SMP in the CSTR, whilst in the SAMBR this was estimated to be 25%. Chromatographic characterization showed that more hydrophobic and high MW organics that absorb at 254 nm were detected in the SAMBR supernatant than in the CSTR. A comparison of chromatograms suggest that the release of extracellular polymers (ECP) and cell lysis may be important sources of SMP in the SAMBR. Electrophoresis results confirmed that there was more soluble protein inside the SAMBR, and showed that the release of ECP by shear or hydrolysis seemed to have contributed to the production of protein-like SMP in both systems.
... Allowing biomass to accumulate on the surface on the filter to achieve stable, feed water was applied to a suitable ozone have been suggested [1][2]. During the decomposition of original organic matter by biofilter, the released soluble microbial products (SMP) in bulk solution should interfere with the removal of the original organic matter, indicating an underestimation of the actual biodegradable organic matter (BOM) removal may be possible [3]. Regarding BDOC analysis, water samples inoculated with different indigenous bacteria, the bioactivity of planktonic bacteria detached from the biofilter, were seldom discussed. ...
Article
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In this work, the excitation-emission fluorescent matrix (EEFM) was used to compare the divergence of fluorescent organic properties of the effluents produced from the operation of the bio-stabilizing filter. Four bio-stabilizing filters were simultaneously operated in the combination of both filtered CCL and FS source waters with ozonation (O3/NPDOC=1) and two different indigenous bacteria taken from CCL and FS source water. It found that, two peak locations, 220-230/330nm, 320-330/410-420nm, existed in the effluent of the four bio-stabilizing filters, and one another peak of 280-290/340 nm was appeared in bio-stabilizing filter using FS source water as a substrate. The fluorescent organic matter, with an excitation wavelength of 220-230 nm and 280-290 nm may be attributed as protein-like, while that of 320-330/410-420nm had the possibility of humic-like. The humic-like matter was accumulated in the effluent from the bio-stabilizing filter during the operational process. Bio-stabilizing filter operated with consistent source water and indigenous bacteria could release higher humic-like fluorescent intensity than that with inconsistent source water and indigenous bacteria.
... La biofiltración está relacionada con estos procesos de biorremediación y consiste en el uso de organismos metabólicamente activos, que se fijan en medios de soporte con el fin de tratar aguas de consumo humano, mostrándose como una opción efectiva (Benner et al., 2013;Yu, Shi, Wei, Ye & Shuting, 2009). Esta tecnología se ha estudiado con biofiltros de carbón activado para remover compuestos orgánicos y subproductos de la cloración (Carlson & Amy, 2000;Liao et al., 2015;Norton & LeChevallier, 2000;Young-Song, Yoon-Jin & Sang-ho, 2007). ...
Article
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p class="p1">El bromacil es un pesticida que se ha encontrado en fuentes de abastecimiento de agua en Costa Rica. Se ha estudiado su degradación en matriz acuosa, principalmente con métodos fotoquímicos. En este artículo se presentan los resultados de un estudio que evalúo la degradación de bromacil por un hongo filamentoso identificado como cepa IT-01 del género Penicillium spp, aislado de suelo contaminado con el herbicida. Se estudió y valoró la eficiencia de remoción del bromacil en un biofiltro a escala laboratorio. Las pruebas se realizaron en el laboratorio de Ingeniería Aplicada de la carrera de Ingeniería Ambiental y el Centro de Investigación y de Servicios Químicos y Microbiológicos (CEQIATEC) del Tecnológico de Costa Rica. La eficiencia de remoción del pesticida al utilizar el microorganismo en un medio acuoso suspendido fue del 50% en 72 horas; sin embargo, al fijarse el hongo en esponja marina y utilizarse en un biofiltro, se obtuvo una eficiencia promedio del 80%, en un tiempo de 18 a 39 segundos. Durante los ensayos del biofiltro se evaluó el tipo de esponja marina como medio de soporte, el efecto de la inoculación del medio filtrante y el tiempo de retención hidráulico. Utilizando el software Minitab, se determinó, con un 95% de confianza, que la inoculación del medio fue el único parámetro que afectó significativamente la eficiencia de remoción del bromacil.</p
... BAPs are products of endogenous respiration by microorganisms. UAPs are more easily biodegraded in comparison with BAPs (Carlson and Amy 2000). ...
Article
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Dissolved organic nitrogen (DON) is a key precursor of numerous disinfection by-products (DBPs), especially nitrogenous DBPs (N-DBPs) formed during disinfection in drinking water treatment. To effectively control DBPs, reduction of the DON concentration before the disinfection process is critical. Traditional biofilters can increase the DON concentration in the effluent, so an improved biofilter is needed. In this study, an improved biofilter was set up with two-layer columns using activated carbon and quartz sand under different influent patterns. Compared with the single-layer filter, the two-layer biofilter controlled the DON concentration more efficiently. The two-point influent biofilter controlled the DON concentration more effectively than the single-point influent biofilter. The improved biofilter resulted in an environment (including matrix, DO, and pH) suitable for microbial growth. Along the depth of the biofilter column, the environment affected the microbial biomass and microbial activity and thus affected the DON concentration.
... DOC in the BAF presented a signicant decline rst, and then gradually stabilized; this result was consistent with the DOC variation in the biolter of relevant literature studies. 19,20 At the media depth of 32 cm, DOC decreased to 7.60 mg L À1 from 20.41 mg L À1 in the inuent, and the DOC removal efficiency at depth of 32 cm was 62.78%. Above the depth of 32 cm, the DOC concentration became stable, and the removal efficiency was not signicant. ...
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To get insight into the components and variations of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in a lab-scale drinking water biological aerated filter (BAF), the concentrations and three-dimensional excitation-emission matrix (3D-EEM) spectrum of DOC and DON were determined and analyzed; peak identification, fluorescence regional integration (FRI) analysis and a parallel factor (PARAFAC) model were applied to analyze the 3D-EEM spectrum. Fluorescent DOC in the BAF mainly existed in the form of humic acids and fulvic acids, and fluorescent DON mainly existed in tryptophan protein form. Protein-like substances accounted for more than 60% of fluorescent organic matter through FRI analysis. Tyrosine and tryptophan-like proteins, and fulvic acid-like substances were effectively removed through the BAF process, while humic acids remained almost unchanged. The results of peak identification, FRI analysis, and PARAFAC model were consistent with each other, especially for FRI and PARAFAC. It is manifest that the FRI technique and PARAFAC model are effective tools for 3D-EEM spectrum analysis. The FRI technique proved to be more suitable to characterize DOC and DON in this study than peak identification and the PARAFAC model.
Article
The profile of dissolved organic nitrogen (DON) was investigated in a full-scale two-stage integrated process of ozonation and biological activated carbon (BAC) filtration. The variation of DON along the media depth of BAC filters was studied comprehensively. The results showed that 48.3% of DON was removed in the two-step processes. Ozone can mineralize organic-N into inorganic-N or nitrogen gas, removing approximately 31% of DON. To determine the variation of DON in the BAC filtration process, DON and other related parameters at different media depths of a BAC filter were studied. The results showed that the concentration of DON decreased from 1.6 to 1.2 mg/L in media depth of 0–10 cm and increased gradually from 1.2 to 1.4 mg/L at deeper depths of the media (10–200 cm). Similarly, the biomass concentration and microbial activity first increased rapidly and then decreased gradually along the media depth of the BAC filter. The proportion of the small molecular weight (20 kDa) DON had the opposite trend. The middle molecular weight fraction (6–20 kDa) of DON was almost unchanged. Soluble microbial products (SMPs) released by bacterial metabolisms might be the main source of DON variation in BAC filters. These SMPs contained aromatic protein-like fractions, which were confirmed by EEM analysis.
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A laboratory membrane bioreactor (MBR) using a submerged polyethylene hollow-fibre membrane module with a pore size of 0.4 microm and a total surface area of 0.2 m2 was used for treating a raw water supply slightly polluted by domestic sewage. The feeding influent had a total organic carbon (TOC) level of 3-5 mg/L and an ammonia nitrogen (NH(3)-N) concentration of 3-4 mg/L. The MBR ran continuously for more than 500 days, with a hydraulic retention time (HRT) as short as 1h or less. Sufficient organic degradation and complete nitrification were achieved in the MBR effluent, which normally had a TOC of less than 2 mg/L and a NH(3)-N of lower than 0.2 mg/L. The process was also highly effective for eliminating conventional water impurities, as demonstrated by decreases in turbidity from 4.50+/-1.11 to 0.08+/-0.03 NTU, in total coliforms from 10(5)/mL to less than 5/mL and in UV(254) absorbance from 0.098+/-0.019 to 0.036+/-0.007 cm(-1). With the MBR treatment, the 3-day trihalomethane formation potential (THMFP) was significantly reduced from 239.5+/-43.8 to 60.4+/-23.1 microg/L. The initial chlorine demand for disinfection decreased from 22.3+/-5.1 to 0.5+/-0. 1mg/L. The biostability of the effluent improved considerably as the assimilable organic carbon (AOC) decreased from 134.5+/-52.7 to 25.3+/-19.9 microg/L. All of these water quality parameters show the superior quality of the MBR-treated water, which was comparable to or even better than the local tap water. Molecular size distribution analysis and the hydrophobic characterisation of the MBR effluent, in comparison to the filtered liquor from the bioreactor, suggest that the MBR had an enhanced filtration mechanism. A sludge layer on the membrane surface could have functioned as an additional barrier to the passage of typical THM precursors, such as large organic molecules and hydrophobic compounds. These results indicate that the MBR with a short HRT could be developed as an effective biological water treatment process to address the urgent need of many developing countries that are plagued by the serious contamination of surface water resources.
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The formation and fate of soluble microbial products (SMP) in membrane bioreactor (MBR) was investigated at various sludge retention times (SRT) for 170 days. The SMP concentration was estimated by feeding glucose, which could be completely degraded, and by measuring the dissolved organic carbon (DOC) of the effluent from MBR. Under the conditions of SRT of 20 days, influent DOC of 112 mg/l and HRT of 6 h, the produced SMP was 4.7 mg DOC/l of which 57% was removed or retained by the membrane. DOC of MBR supernatant increased during 100 days and then gradually decreased. Specific UV absorbance showed that the accumulated compounds had a portion of larger, more aromatic, more hydrophobic and double-bond-rich organics, which originated from the decayed biomass. Molecular weight distributions of SMP in MBR supernatant showed that the acclimated microorganisms in a long SRT could decompose high molecular weight organics, it caused the shift of molecular weight distributions of SMP to a lower range. During the operation period, enumeration of active cells in the MBR showed that microbial inhibitions by accumulated SMP was not observed.
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Thesis (Ph. D.)--Arizona State University, 2007. Includes bibliographical references (leaves [350]-363).
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Phosphorus was added as a nutrient to bench-scale and pilot-scale biologically active carbon (BAC) reactors operated for perchlorate and nitrate removal from contaminated groundwater. The two bioreactors responded similarly to phosphorus addition in terms of microbial community function (i.e., reactor performance), while drastically different responses in microbial community structure were detected. Improvement in reactor performance with respect to perchlorate and nitrate removal started within a few days after phosphorus addition for both reactors. Microbial community structures were evaluated using molecular techniques targeting 16S rRNA genes. Clone library results showed that the relative abundance of perchlorate-reducing bacteria (PRB) Dechloromonas and Azospira in the bench-scale reactor increased from 15.2% and 0.6% to 54.2% and 11.7% after phosphorus addition, respectively. Real-time quantitative PCR (qPCR) experiments revealed that these increases started within a few days after phosphorus addition. In contrast, after phosphorus addition, the relative abundance of Dechloromonas in the pilot-scale reactor decreased from 7.1 to 0.6%, while Zoogloea increased from 17.9 to 52.0%. The results of this study demonstrated that similar operating conditions for bench-scale and pilot-scale reactors resulted in similar contaminant removal performances, despite dramatically different responses from microbial communities. These findings suggest that it is important to evaluate the microbial community compositions inside bioreactors used for drinking water treatment, as they determine the microbial composition in the effluent and impact downstream treatment requirements for drinking water production. This information could be particularly relevant to drinking water safety, if pathogens or disinfectant-resistant bacteria are detected in the bioreactors.
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A comprehensive investigation was made in this study on the variation of dissolved organic nitrogen (DON) during a whole backwashing cycle of the biofiltration for drinking water treatment. In such a cycle, the normalized DON concentration (C(effluent)/C(influent)) was decreased from 0.98 to 0.90 in the first 1.5h, and then gradually increased to about 1.5 in the following 8h. Finally, it remained stable until the end of this 24-hour cycle. This clearly 3-stage profile of DON could be explained by three aspects as follows: (1) the impact of the backwashing on the biomass and the microbial activity; (2) the release of soluble microbial products (SMPs) during the biofiltration; (3) the competition between heterotrophic bacteria and nitrifying bacteria. All the facts supported that more DON was generated during later part of the backwashing cycle. The significance of the conclusion is that the shorter backwashing intervals between backwashing for the drinking water biofilter should further decrease the DON concentration in effluent of biofilter.
Article
Biofiltration can be an effective drinking water treatment process when ozonation is practiced beforehand. The objectives and therefore the designs of these two processes are usually not related to biological treatment goals, and no effort has been made to determine the compatibility of the goals of these integrated treatment processes. The optimal application of ozone (O3) for disinfection is the minimum dose that provides a target level of microorganism inactivation. This dose was equivalent to the optimal O3 dose for biological treatment, defined as the minimum dose that would achieve the maximum relative BDOCrapid removal. Additionally, the O3 process is limited with respect to controlling the formation of BDOCrapid. Increasing the O3 dose beyond the optimal dose will result in little additional BDOCrapid formation, little additional release of biodegradable dissolved organic carbon to the distribution system, and an increase in the cost of operation. A conceptual approach for optimizing the O3 and biofiltration processes for biological treatment objectives is described for three case studies. The results indicate that biological treatment goals can be satisfied to a large degree while simultaneously meeting other drinking water treatment objectives such as disinfection and particle removal.
Article
This article examines two types of membrane bioreactors (MBRs): attached growth membrane bioreactors with media (MBR-A); and suspended growth membrane bioreactors without media (MBR-S) to comparatively evaluate microbial characteristics of and efficiency of pollutant removal of contaminants in Yangtze raw river water. The results indicated that both MBRs were highly efficient at removing pollutants from real raw water. Analysis of the water samples' biomass and biological activities showed that suspended microorganisms in MBR-A predominated in the biomass phase while the adhesive microorganisms in MBR-S did not. As shown by Phospholipid Fatty Acid (PLFA) analysis, higher total biological activity in MBR-A results from the abundance of microorganisms and higher proportion of Gram-negative bacterium. Extracellular Polymeric Substances (EPS) analysis showed that MBR-S demonstrated greater membrane flux while the amount of EPS was higher in MBR-S than in MBR-A. Consequently, EPS is likely not the primary factor in membrane fouling.
Article
This study conducted a two-stage experiment. The first stage attempted to establish biostable filter beds. Two parameters, total bacterial count (TBC) and non-purgeable dissolved carbon (NPDOC), measured by passing through a 0.2μm membrane filter, were selected to compare the difference of biostability of a filtration system with recirculation with different O3-to-NPDOC ratios of filtered water. The excitation emission fluorescence matrix (EEFM) was used as an effective tool for understanding information regarding organic characteristics by comparing source filtered water before and after ozonation and the effluent during biostablizing filter. During the second stage, a biostable filter was used to compare differences in biodegradability of ozonated products sodium oxalate and sodium acetate. Experimental results demonstrate that both parameters, NPDOC removal and TBC, can be utilized to evaluate the biostabilty of a filter bed. With each parameter, a plateau was reached in roughly 20days. The source water from Chen Ching Lake (CCL) contained a protein-like substance determined by the EEFM. This protein-like substance was also destroyed by O3/NPDOC = 1.1. Soluble microbial products (SMPs) released from the biostablizing filter into the effluent have two peaks in the EEFM, identified as protein-like and humic-like acid. The NPDOC removal for the biostabilizing filter using O3/NPDOC = 1.7 was less than that using O3/NPDOC = 1.1. Bacterial counts in the effluent from the biostabilizing filter using O3/NPDOC = 1.1 was better than that of O3/NPDOC = 1.7. This difference can be explained by the high ratio of O3/NPDOC producing by-products of ozonation that were easily utilized by microorganisms; however, filter bed also released relatively more SMPs owing to increased proliferation of microorganisms attached to glass pellets in the filter. Regarding the differences in decomposition of the by-products of ozonation by the biostable filter, such as sodium oxalate, the NPDOC removal at O3/NPDOC = 1.1 was better than that at O3/DOC = 1.7. This phenomenon can be explained as previously mentioned.
Chapter
IntroductionGeneral ApproachSome Adsorbents Used in Water and Wastewater TreatmentsAdsorption in a Batch ContactorFlow of Water Through an Adsorbent BedBreakthrough Curves in Continuous Adsorption ProcessesBiological Activated Carbon FiltersRegeneration of Spent AdsorbentsSome Applications of Adsorption in Water and Wastewater TreatmentsCost
Article
Membrane fouling is one of the major obstacles for wide applications of MBRs. Over the past decade, the behaviors of colloidal and soluble substances have attracted much attention, and intensive efforts have been dedicated to the clarification of their role in membrane fouling. However, to date, the conclusions are often different and even controversial. The review is attempted to clarify their interrelations and to eliminate some confusions by reviewing the recent literature. The similarities and differences of those potential foulants are analyzed through comparing definitions, extraction methods, fouling indicators, and fouling behaviors. The implications of future research directions are also discussed in this paper.
Article
The objective of this study is to further evaluate the relationship between removal effect of dissolved organic pollutants (DOC) and their characteristics (biodegradability, adsorbability and molecular size distribution) in different running stage of BAC filter. The experimental results showed that during early period of operation, BAC filter mainly removed adsorbable DOC (that is ADOC), but after continuously running for five months, the main body to be removed by BAC filter was adsorbable and biodegradable DOC (that is A&BDOC), and the distribution of molecular weight for this fraction of DOC was 3kD~1kD and
Article
Dissolved organic nitrogen (DON) is currently considered as one of the most important parameters in drinking water treatment due to its potential to form toxic nitrogenous disinfection by-products (NDBPs). A comprehensive investigation was made in this study on the variation of DON in a full-scale drinking water treatment plant with a treatment train of coagulation/ sedimentation, biofiltration and disinfection. The results showed that DON could be removed effectively by coagulation/ sedimentation and disinfection, while biofiltration increased the DON concentration significantly. To determine the mechanism of DON increase, DON and other related parameters at different media depths of the biofilter were studied. The results showed that the DON concentration in the biofilter presented a rapid decrease from 0.73 to 0.44 mg l -1 in the top media (0-10 cm), and a slow increase from 0.44 to 1.08 mg l -1 in the bottom media (10-100 cm). Soluble microbial products (SMPs) released by bacterial metabolism might be a main source of the DON in the biofilter. These SMPs contained aromatic protein-like fractions, which were confirmed by EEM analysis. © IWA Publishing 2012 Journal of Water Supply: Research and Technology-AQUA.
Article
The membrane bioreactor (MBR) systems have been increasingly used in water treatment in recent years. However, fouling by soluble microbial products (SMP) remains one of the key performance limitations for more widespread applications. A brief review concerning the characterization, production, affecting factors, components of SMP in MBR systems is presented.
Article
The effluent from a continuous-flow stirred tank reactor (CSTR) treating synthetic wastewater was used as an alternative carbon source to glucose for algal biomass and biodiesel production. The influence of the effluent on microalgal cell growth and lipid yield, as well as the utilization of volatile fatty acids (VFAs) in the effluent were investigated. The results indicate that C. protothecoides can proliferate in the CSTR effluent and accumulate biolipid. The final lipid content of the culture with the effluent feeding was 27 ± 1.11 % after 168 h cultivation in flasks, which was higher than that with glucose of the same COD concentration. Valeric acid, ethanol, and butyric acid were favorable carbon sources for cell growth. The soluble microbial products (SMP) can be used as a carbon source for cell growth, and the existence of SMP could protect the cell from the inhibition caused by strong VFAs and improve the utilization of VFAs.
Article
Due to its potential to form toxic nitrogenous disinfection byproducts (N-DBPs), dissolved organic nitrogen (DON) is considered as one of the most important parameters in wastewater treatment plants (WWTP). This study describes a comprehensive investigation of variations in DON levels in orbal oxidation ditches. The results showed that DON increased gradually from 0.71 to 1.14 mg I(-1) along anaerobic zone, anoxic zone, aerobic zone 1 and aerobic 2. Molecular weight fractionation of DON in one anaerobic zone and one aerobic zone (aerobic zone 2) was performed. We found that the proportion of small molecular weight (<6 kDa) decreased and large molecular weight (> 20 kDa) showed opposite trend. This variation may have been caused due to the release of different types of soluble microbial products (SMPs) during biological processes. These SMPs contained both tryptophan protein-like and aromatic protein-like substances, which were confirmed by three-dimensional excitation-emission matrix (EEM) analysis.
Article
A comprehensive study on formation and characteristics of soluble microbial products (SMP) during drinking water biofiltration was made in four parallel pilot-scale ceramic biofilters with acetate as the substrate. Excellent treatment performance was achieved while microbial biomass and acetate carbon both declined with the depth of filter. The SMP concentration was determined by calculating the difference between the concentration of dissolved organic carbon (DOC), biodegradable dissolved organic carbon (BDOC) and acetate carbon. The results revealed that SMP showed an obvious increase from 0 to 100 cm depth of the filter. A rising specific ultraviolet absorbance (SUVA) was also found, indicating that benzene or carbonyl might exist in these compounds. SMP produced during this drinking water biological process were proved to have weak mutagenicity and were not precursors of by-products of chlorination disinfection. The volatile parts of SMP were half-quantity analyzed and most of them were dicarboxyl acids, others were hydrocarbons or benzene with 16-17 carbon atoms.
Dissolved organic nitrogen derived from soluble microbial products (SMPs-DON) generated during the drinking water biological treatment process poses a great threat to water supply safety due to the potential carcinogenic risk. To further study the production mechanism and characteristics of SMPs-DON in drinking water biological aerated filtration (BAF), Illumina MiSeq sequencing is applied to characterize the microbial community. In addition, an excitation–emission matrix combined with the parallel factor model (EEM-PARAFAC) and gel filtration chromatography (GFC) are used to analyze the component and molecular weight (MW) distribution of the SMPs-DON. Results showed that the production of SMPs-DON in drinking water BAF can be explained using Illumina MiSeq sequencing from the perspective of the microbial community. Also, according to the EEM-PARAFAC analysis, the fluorescence intensity scores of fulvic-like and humic-like substances were almost unchanged, whereas the scores of protein-like substances first increased and then decreased, which was consistent with the variation in the DON concentration. SMPs produced initially primarily consisted of macromolecules with MW >20 kDa, and then they were degraded and small molecular SMPs with MW <5 kDa accumulated. This study provides theoretical guidance and technical support for ensuring drinking water safety and reducing secondary pollution risks from drinking water biological treatment.
Conference Paper
Present remote controls for interactive digital television (iTV) strongly limit interaction possibilities. For example they do not support the interaction style of direct manipulation. Recent advances of the marker less motion capture technology make it possible to do body gesture interaction conveniently in digital home and life, especially in TV-based applications. However, there are few established conventions in body gesture design for such applications. In this paper, we report a guess ability study on eliciting intuitive gestures from non-professional users to perform tasks in TV based applications in a setting mimicking living rooms. Our results show that consensus exists among subjects. With this study, we present a taxonomy for body gestures, an end-user gesture set, qualitative observations, and implications for gesture design. Our results will help designers create more available gesture set and bring body gesture closer to digital home applications.
Article
The relationship between soluble microbial products (SMPs) and extracellular polymeric substances is described, and the characteristics of SMPs in the biological wastewater treatment process, including molecular weight distribution, metal-chelating property, biodegradability, biotoxicity, and membrane fouling, are investigated. The SMPs produced by autotrophs are degradable and utilizable for heterotrophs, thereby confirming the biodegradation of SMPs. Soluble microbial product models are designed through three approaches: establishment of SMP kinetic models or combination with Monod equations, incorporation of SMP generation and degradation into the unified theory raised by Laspidou and Rittmann (2002a), and introduction of the concept of SMP into activated sludge models. The effects of process parameters on SMP concentration are elaborated, based on the optimum biological treatment process operating parameters that can effectively minimize SMP production. The progress of SMP research in water biotreatment systems is presented, and suggestions for future studies are made.
Chapter
Haloacetamides (HAcAms), an emerging class of nitrogenbased disinfection by-products (N-DBPs), have been frequently identified in drinking waters. However, there is a limited understanding on the performance of different treatment technologies in the control of HAcAms. The objective of this study was to evaluate the potential of traditional and advanced treatment technologies, including three pre-treatment processes (i.e., powdered activated carbon [PAC] adsorption, KMnO4 oxidation, and biological contact oxidation [BCO]), two combined conventional treatment methods (i.e. coagulation - inclined plate sedimentation [IPS]-filtration, and coagulation-dissolved air flotation [DAF]-filtration), and an advanced processes (i.e. integrated ozone and biological activated carbon [O3-BAC] treatment), for removing the precursors of HAcAms while minimizing the formation of other typical N-DBPs in water. Among the three pre-treatment processes, PAC adsorption could effectively remove the precursors of chloroform (CF) (42.7%), dichloroacetonitrile (DCAN) (28.6%), dichloroacetamide (DCAcAm) (27.2%) and trichloronitromethane (TCNM) (35.7%), advantageous over KMnO4 oxidation and/or BCO process. In contrast, the removal efficiency of dissolved organic carbon (DOC) by the BCO process (76.5%) was superior to that by PAC adsorption (69.9%) and KMnO4 oxidation (61.4%). However, BCO increased the dissolved organic nitrogen (DON) concentration, thereby leading to the formation of more N-DBPs during the subsequent chlorination. Soluble microbial products including numerous DON compounds produced as a result of the BCO treatment were observed to play an essential role in the DCAcAm formation. Between the conventional processes, the removal of algae, DON, DOC and UV254 by the coagulation-DAF-filtration was better than the coagulation-IPS-filtration. On the average, the former achieved the removal of 53% DOC, 53% DON and 31% UV254, while the latter only removed 47% DOC, 31% DON and 27% UV254. Additionally, the coagulation-IPS-filtration removed less low molecular weight organic molecules than the coagulation-DAF-filtration process. Consequently, the concentrations of CF, DCAcAm and DCAN formed from the coagulation-DAF-filtration treated water reached 13, 1.5 and 4.7 μg/L during chlorination, respectively, which were lower than those from chlorination of the coagulation-IPS-filtration treated water (17 μg/L CF, 2.9 μg/L DCAcAm and 6.3 μg/L DCAN). Among the advanced treatment processes, O3-BAC significantly improved the removal of turbidity, DOC, UV254, NH+4-N, and DON by 98â€"99%, 58â€"72%, 31â€"53%, 16â€"93% and 35â€"74%, respectively, and enhanced the removal efficiency of the DBP precursors. However, this option was almost ineffective in removing TCNM and DCAcAm precursors. Ozonation alone could not substantially reduce the DCAcAm formation, and increased the TCNM formation potential (FP). However, it chemically altered the molecular structures of the precursors and increased the biodegradability of N-containing organic compounds. Consequently, the subsequent BAC filtration dramatically reduced the formation of the both TCNM and DCAcAm, thus highlighting a synergistic effect of O3 and BAC. Additionally, O3-BAC was effective at controlling the formation of total organic halogen, which is recognized as an indicator of the formation of unidentified DBPs. Of note, more N-DBP precursors entered into the post-BAC water without pre-ozonation, leading to the formation of more N-DBPs during chlorination, compared with a control group with the pre-ozonation was continuously operated. Moreover, higher DBP FP was observed in the effluent of the BAC filter without pre-ozonation than the FP in the influent of the BAC filter. Therefore, while the intermittent operation of pre-ozonation may have cost and other operational benefits (bromate control), these may be outweighed against the increased N-DBP formation and potential N-DBP associated health risks.
Article
Dissolved organic nitrogen (DON) is an issue for the water field primarily due to the formation of disinfection by-products of health concern, and its potential role in membrane fouling. This article reviews the following DON issues: (1) analytical measurement, (2) occurrence, (3) structural composition, and (4) treatability during potable water treatment. There is no direct measurement for DON, rather DON is calculated by the difference between total dissolved nitrogen and inorganic nitrogen ions. DON concentrations range from <0.1 to >10 mg N/l with a median value of ∼0.3 mg N/l in surface waters. DON sources include wastewater discharges, agricultural fertilizers, algae, forest litter and soils, DON is comprised of a broad spectrum of molecular weight compounds encompassing multiple N-containing functional groups. Carbon to nitrogen ratios (C/N or DOC/DON) range between 5 and 100 mg C/mg N (median ∼15 mg C/mg N), and may be a good indicator of organic matter sources. During chlorination higher org-N content leads to (1) increasing chlorine demand, (2) production of di-HAA>tri-HAA, (3) production of HAA>THM, and (4) production of higher levels for halogenated (nitromethanes, HANs) and non-halogenated (NDMA) org-N DBPS. Information on DON removal during potable water treatment is lacking and should be a focus of future research.
Article
This paper investigated the fate of organic pollutants in each unit of a full-scale O3-BAC (Biological Activated Carbon) drinking water treatment plant with micro-polluted raw water under different temperatures . Total organic matters were largely removed with low DBPs (disinfection by-products) formed. Large molecules were broken into smaller ones by O3 and middle sized ones totally removed. Concentration of polysaccharide decreased except under high temperature. Small molecule contaminant species of refractory industrial additives, hydrocarbons, aromatics, herbicides, possible DBPs, etc. were detected. Some species passed through treatment process, some were removed and also new species formed.
Conference Paper
Dissolved organic nitrogen (DON) can form toxic nitrogenous disinfection byproducts (N-DBPs) relatively readily. In this way, DON content can have profound effects on the effluent of wastewater treatment plants (WWTP). This study describes a comprehensive investigation of variations in dissolved organic nitrogen levels in orbal oxidation ditches. The results showed that DON was increased gradually from 0.71 to 1.14 mg/l along anaerobic zone, anoxic zone, aerobic zone 1 and aerobic 2. We performed molecular weight fractionation of DON in one anaerobic zone and one aerobic zone (aerobic zone 2). We found far fewer small-molecular-weight DONs (20 kDa). This variation may have been caused by the release of different types of soluble microbial products (SMPs) during biological processes might be a main reason for the DON variation in orbal oxidation ditch. These SMPs contained both tryptophan-like and aromatic protein substances, as indicated by three-dimensional excitation-emission matrix (EEM) analysis.
Article
Full-text available
To maintain the biological stability of drinking water during distribution in large, complex networks, high standards have to be met—namely, low bacterial densities and low levels of biodegradable organic carbon. Second-stage granular activated carbon (GAC) filtration (without regeneration of carbon) is used for this purpose at the Choisy-le-Roi, Paris, France, treatment plant. Effective removal of dissolved organic carbon has been observed with such filtration—mainly because of a reduction in the biodegradable organic carbon. To study the microbial processes involved in this removal, new methods based on the use of radio-labeled tracers have been developed in order to measure the bacterial biomass and activity associated with GAC. Para mantener la estabilidad biológica del agua potable durante la distribución en sistemas grandes y complejos, se tienen que lograr normas altas, como por ejemplo, bajas densidades de bactérias y baj os niveles de carbón orgánico biodegradable. Se usa para este fin la segunda etapa de filtración con carbono granular activado (GAC) (sin la regeneración dei carbón) en la planta de tratamiento Choisy-le-Roi, París, Francia. Se ha observado una remoción efectiva dei carbón orgánico disuelto con està filtración—debido primordialmente a la reducción dei carbón orgánico biodegradable. Para estudiar los procesos microbianos envueltos en esta remoción, se han desarrollado nuevos métodos basados en el uso de trazadores marcados por radio para medir la biomasa de las bacterias y la actividad asociada con el GAC.
Article
Full-text available
This book organized under the following chapters: Fundamental aspects; Practical application of ozone: Principles and case studies; Engineering aspects; Operating an ozonation facility; Economics of ozone systems: New installations and retrofits; and Ozone system terminology, measurements and conversions.
Article
Full-text available
Improvements in the analysis of lipid-bound phosphates resulted in a simplified and sensitive method for determining microbial biomass in sediments. Sensitivity was enhanced over previous methods by use of a dye, malachite green, which when complexed with phosphomolybdate at low pH has a high extinction coefficient (at 610 nm). The use of a persulfate oxidation technique to liberate phosphate from lipids increased the simplicity and safety of the method relative to the traditional perchloric acid digestions. The modified method was both accurate (yielding quantitative recoveries of cells added to sediments) and precise (coefficient of variation of less than 5% for cells and sediments). A comparison with an epifluorescence technique indicated that the analysis of lipid-bound phosphate was more rapid and less tedious and could be successfully applied to a wider variety of sediment types. An estimate of the lipid-bound phosphate-to-carbon conversion factor based on a diverse enrichment culture from sediments suggested that previous factors for pure cultures may have been too low.
Chapter
A direct ion chromatography method was applied to the determination of short-chain carboxylic acids (acetic, formic, and oxalic) in drinking water treated with ozone. These organic acids were separated on an anion exchange column (Ionpac AS11; Dionex Corp., Sunnyvale, CA), using a 50-μL sample loop. Samples were collected from the ozone pilot plant of the Metropolitan Water District of Southern California to study the formation of carboxylic acids and their removal by two different types of biologically active filters. Preliminary results indicate that the carboxylic acid concentrations out of the ozone contactor were the greatest for oxalic acid (∼380 μg/L), followed by formic (∼130 μg/L) and acetic (∼60 μg/L) acid, and that the sum of the three acids on a carbon basis was ∼160 μg/L. Approximately 80 percent of these carboxylic acids were removed during biofiltration. Aldehydes and assimilable organic carbon (AOC) were also measured from the same batch of samples, and the removal percentages were similar to those obtained in the carboxylic acid analyses. The percent fractions of AOC at the ozone effluent for combined carboxylic acids and combined aldehydes were 36.9 and 3.7 percent, respectively.
Article
The formation of soluble microbial products was evaluated in batch reactors using radiolabeled 14C-phenol and 14C-glucose. Soluble microbial products, SMP, resulted from intermediates or end products of substrate degradation and endogenous cell decomposition. On an organic carbon basis, the SMP produced after 48 hours averaged 14.7 (±3.7) percent of the initial phenol and 3.1 (±0.4) percent of the initial glucose. The SMP were categorized as substrate utilization products, having a biodegradable and non-biodegradable fraction, and biomass associated products, which were only non-biodegradable. A model was developed based on kinetic relationships between several macroscopic compartments, which consisted of the initial substrate, cell mass, and the three SMP categories. Based on the experimental data, zero and first order kinetics were sufficient to describe the disappearance of the initial substrates and the net SMP, i.e., total SMP produced less SMP biodegraded to yield CO2 and/or new biomass. Both phenol and glucose adhered to the same kinetic model, but the rate constants were considerably different.
Article
A critical evaluation of the characteristics of soluble microbial products (SMP) indicates that SMP is comprised of many different types and sizes of molecules and is biodegradable. A portion of SMP is formed at a rate proportional to the rate of substrate utilization (UAP), while the rest is formed at a rate proportional to the concentration of active biomass (BAP). These characteristics are incorporated into a mathematical model that includes the following components: substrate utilization and biomass growth according to Monod kinetics, SMP formation kinetics in proportion to substrate utilization rate and to biomass accumulation, and SMP degradation according to a semi-empirical multi-component degradation model. The SMP formation/degradation model successfully describes the fractional conversion of substrate into SMP, including the observed trends of increasing conversion at high and low sludge ages. In addition to activated sludge, the model is applied to anaerobic treatment and to biofilm processes.
Article
Activated sludge systems treating supplemented domestic wastewater were used to determine the effect of mean cell residence time, ${\rm O}_{{\rm c}}$ , on the chemical characteristics of effluent organic matter. ${\rm O}_{{\rm c}}$ values ranged from 0.8 to 19.4 days. Membrane filtration and ultrafiltration techniques were used to separate effluent organic matter into two fractions-slime organic matter and dissolved organic matter. Significant reduction in filtrable effluent chemical oxygen demand concentration was achieved with increasing ${\rm O}_{{\rm c}}$ through reduction in the slime and dissolved organic fractions. Effluent slime constituted approximately 75% of effluent organic matter. As ${\rm O}_{{\rm c}}$ increased, slime organic matter decreased in molecular size with low molecular weight slime (mol wt = 500 to 10 000) comprising 95% of total slime organic matter at ${\rm O}_{{\rm c}}$ = 19.4 days. Changes that occurred in slime and dissolved organic fractions were within the limits of variation found with full scale activated sludge systems treating domestic wastewaters. Furthermore, results of the study indicate that variations in ${\rm O}_{{\rm c}}$ could account for variations indicated in effluent organic characteristics for full-scale systems. A hyperbolic function, that is, ${\rm O}_{{\rm c}}{}^{1}$ - $({\rm AS})({\rm K}-{\rm S})^{-1}$ , was used to relate total, slime and dissolved organic matter to ${\rm O}_{{\rm c}}$ .
Article
Using data from two pilot-scale studies and one full-scale investigation, this article demonstrates that the removal rate in biological water treatment is proportional to the influent concentration to the bioreactor, i.e., a first-order process. This is true not only for measures of biodegradable organic matter, e.g., assimilable organic carbon, but also for precursors of chlorination by-products such as trihalomethanes. The slope of the removal rate versus the influent concentration relationship is termed the average specific removal rate, rAS. When data were available from different studies, the rAS values tended to fall in the same range. With a first-order model, the performance of biological treatment in a given situation can be estimated from limited data. The model is suggested as an approach for the preliminary design of bioreactors for drinking water treatment.
Article
This article describes the overall development, including formulation and calibration, of linear and nonlinear multiple regression models for predicting total trihalomethane formation potential and kinetics during the chlorination of natural waters. The rationale behind each model formulation is discussed, and statistics relating to the calibration of each model are presented. The testing and attempted validation of these models are also addressed. Each model is subjected to a sensitivity analysis and a validation analysis using data derived from the literature. Este artículo describe el desarrollo completo, incluyendo formulación y calibración, de modelos de regresión en múltiplo lineal y no lineal para predecir potencial de formación y cinéticas totales de trihalometanos durante la clorinación de aguas naturales. Se discuten las razones tras la formulación de cada modelo y se presentan estatisticas relacionadas a la calibración de cada modelo. Se discuten las pruebas y proyecto de validación de estos modelos. Se analiza la sensitividad y validación de cada modelo usando información obtenida de la literatura.
Article
The concentration and nature of natural organic matter (NOM) influence the processes selected for water treatment plants. Water supplies containing NOM dominated by humic substances require careful design and operation of the chemical pre-treatment step of coagulation. Humic substances in untreated waters exert a greater demand for chemical coagulants compared to particulate matter, and their removal is important for health reasons because they are precursors to trihalomethanes and other disinfection by-products. Furthermore, coagulation affects the performance of downstream particle separation processes of clarification (sedimentation or flotation) and filtration.
Article
Bench scale activated sludge reactors with a solids retention time of 9 days were operated at all combinations of two levels of pH, dissolved oxygen (DO) concentration and feed type (pH 6 and 8; DO 1 and 7 mgl−1; simple and complex feed). Long-term composite samples were collected and adjusted to neutral pH and equal concentrations of alkalinity and ammonia nitrogen. The molecular weight distributions of the soluble organic carbon (SOC) in the samples were determined by ultrafiltration through membranes with nominal rejection values of 1000, 10,000, 25,000 and 100,000. The distributions were generally bimodal with the bulk of the SOC in the largest and smallest fractions. Following ozonation to a residual of 0.30–0.35 mg 1−1 after 5 min contact, the distributions were shifted so that more of the SOC appeared in the lowest molecular weight fraction although significant amounts remained in the other fractions. When samples were breakpoint chlorinated to a residual of 5–10 mg l−1 free available chlorine after 2 h contact, very little high molecular weight material remained and almost all of the SOC appeared in the low molecular weight fraction. By using 36Cl during breakpoint chlorination it was also possible to evaluate the distribution of organically bound chlorine among the molecular weight fractions and this revealed that the bulk of it was associated with organics having molecular weight less than 1000.
Article
In order to determine whether the influent substrate concentration exerts an effect upon the kinetics of soluble substrate removal by natural microbial populations growing in continuous culture experiments were run using a multicomponent substrate. A two-level factorial experimental design was employed with reactor dilution rate and influent substrate concentration as the independent variables. Analysis of the results indicated that both variables exerted a significant effect (1% level) upon the effluent soluble COD. It was possible to model the system using the linear approximation of the Monod equation resulting in an equation of the general form: The findings of the study indicate that engineers responsible for the design and operation of wastewater treatment facilities should consider the influent substrate concentration when choosing a mean cell residence time for the system.
Article
Soluble microbial products (SMP) formation kinetics were investigated by employing a laboratory-scale biofilm reactor and naturally-grown oligotrophs. The experimental results indicated that the majority of effluent soluble organic carbon(SOC) was SMP, while only a small fraction of the effluent SOC was the residual original substrate. Utilization-associated products (UAP), which were produced directly from substrate metabolism, were more important than biomass-associated products (BAP), which were produced by basic metabolism. The SMP contained mainly high-molecular-weight organic compounds, although the organic carbon source to a biofilm reactor was a low-molecular-weight compound. The steady-state concentrations of the effluent SMP and SOC were directly proportional to the influent substrate concentrations in this study. An extended steady-state biofilm model was developed by incorporating into the steady-state biofilm model an SMP formation model based on two types of SMP (i.e. UAP and BAP). The model described successfully the experimental substrate utilization, SMP formation, and the removal of total soluble organic matter (SOC).
Article
Thesis (Ph. D.)--University of Colorado, 1996. Includes bibliographical references (leaves [267]-276).
Article
The production of soluble microbial products (SMP) in anaerobic systems was evaluated using chemostat reactors. Results from steady-state and tracer experiments with (14)C-glucose and (14)C-acetate showed that significant amounts of SMP were produced during the acidogenesis of glucose, but that SMP did not accumulate during methanogenesis from acetate. In addition, at a retention time of 40 days, SMP comprised almost all of the effluent COD from the glucose-fed chemostat. For shorter retention times, as low as 10 days, the SMP concentration remained almost constant, but its significance in the effluent COD was reduced due to the accumulation of intermediate volatile fatty acids. The results from a (14)C-tracer experiment in the glucose-fed chemostat were used to evaluate the importance of including SMP formation and degradation in kinetic modeling of the methanogenic chemostats. Three models were evaluated: a model without SMP production, a model with SMP production but no degradation, and a model with SMP production and degradation, The results of this kinetic analysis indicate that the model that includes SMP production and degradation was the only one able to adequately represent the fate of (14)C in the tracer experiment. The kinetic parameters were successfully used to predict steady-state concentrations of SMP and to characterize the formation and degradation characteristics of the SMP.
Ozone disinfection by-products: optimization of the PFBHA derivatization method for the analysis of aldehydes
  • M J Sclimenti
  • S W Krasner
  • W H Glaze
  • H S Weinberg
Sclimenti M. J., Krasner S. W., Glaze W. H. and Weinberg H. S. (1990) Ozone disinfection by-products: optimization of the PFBHA derivatization method for the analysis of aldehydes. In Proceedings of 1990 AWWA WQTC, San Diego, CA.
The formation of ®l-ter removable BOM during ozonation
  • K H Carlson
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