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Treatment of ozonated water in biofilters containing different media
Abstract
Four parallel biofilters were tested for treatment of ozonated humic water. Two of them contained Kaldnes plastic cylinders (KMT media), one marble and one expanded clay aggregates (Filtralite NC) as biofilm media. Dual-media filter was used for removal of bacteria from biofilter effluents. After four months of operation, average TOC removal was 37-38% and COD(Mn) removal was 43-45% in the ozonation/biofiltration process. Ozonation removed 83% of colour from the raw water. Over 83% removal of ozonation by-products (aldehydes and ketoacids) was also achieved. Biofiltration increased the levels of heterotrophic bacteria in the water but they were reduced by 88% in the dual-media filter. The biofilter media did not have significant effect on treatment efficiency at the empty bed contact time of 30-40 min.
... For example, biofiltration has also been used in conjunction with other treatment technologies such as ozonation. [22][23][24][25] In their recent work, Bacaro et al have expanded the treatment by ozonation with biofiltration studies to chloramines using a pilot scale system. 26 Current reports show that the biofiltration process is easier to operate and is cost effective in removing VOC air pollutants. ...
In this study, the biodegradation of a mixture of two trihalomethane (THM) compounds, chloroform (CF) and dichlorobromomethane (DCBM), was evaluated using two laboratory‐scale biotrickling filters (BTFs). The two BTFs, hereby designated as “BTF‐A” and “BTF‐B,” were run parallel and used ethanol as co‐metabolite at different loading rates (LRs), and a lipopeptide‐type biosurfactant that was generated by the gram‐positive bacteria, Surfactin, respectively. The results using BTF‐A showed that adding ethanol at a higher rate of 4.59 g/(m3 h) resulted in removal efficiencies of 85% and 87% for CF and DCBM, respectively. Conversely, for the same LR, the use of Surfactin without ethanol (BTF‐B) showed comparable removal efficiencies of 85% and 80% for CF and DCBM, respectively. The maximum rate constant for CF and DCBM for the BTF‐A was 0.00203 s−1 and 0.0022 s−1, respectively. For the same THMs LR, similar reaction rate constants resulted for the BTF‐B. Further studies were conducted to investigate and understand the microbial diversity within both BTFs. The result indicated that for BTF with co‐metabolite, Fusarium sp. was the most dominant fungi over 98% followed by F. Solani with less than 2%. F. oxysporum and Fusarium sp. were instead the dominant fungi for the BTF with Surfactin. Before introducing the Surfactin into the BTF, the batch experiment was conducted to evaluate the effectiveness of synthetic surfactant as compared to a biosurfactant (Surfactin). In this regard, vials with Surfactin showed better performance than vials with Tomadol 25‐7 (synthetic surfactant).
... Comparable results were also reported in other previous investigations in which several types of media were used as filling material in biofiltration systems (Hozalski et al. 1995;Melin et al. 2000). The data representing the COD profile over the course of the biofilter operation is shown in Fig. 2b. ...
The combination of biological and chemical oxidation processes is an interesting approach to remove ready, poor, and non-biodegradable compounds from complex industrial wastewaters. In this study, biofiltration followed by H2O2/UV oxidation (or microfiltration) and final reverse osmosis (RO) step was employed for tertiary treatment of an oil refinery wastewater. Biofiltration alone allowed obtaining total organic carbon (TOC), chemical oxygen demand (COD), UV absorbance at 254 nm (UV254), ammonium, and turbidity removal of around 46, 46, 23, 50, and 61 %, respectively. After the combined biological-chemical oxidation treatment, TOC and UV254 removal amounted to 88 and 79 %, respectively. Whereas, the treatment performance achieved with different UV lamp powers (55 and 95 W) and therefore distinct irradiance levels (26.8 and 46.3 mW/cm(2), respectively) were very similar and TOC and UV254 removal rates were highly affected by the applied C/H2O2 ratio. Silt density index (SDI) was effectively reduced by H2O2/UV oxidation, favoring further RO application. C/H2O2 ratio of 1:4, 55 W UV lamp, and 20-min oxidation reaction corresponded to the experimental condition which provided the best cost/benefit ratio for TOC, UV254, and SDI reduction from the biofilter effluent. The array of treatment processes proposed in this study has shown to be adequate for tertiary treatment of the oil refinery wastewater, ensuring the mitigation of membrane fouling problems and producing a final effluent which is suitable for reuse applications.
... Many studies have been done on filters media for enhancing treated drinking water (El-Taweel and Ali 2000;Melin et al. 2000;Babu and Chaudhuri 2005;Pawlowicz et al. 2006). ...
Several media have been used in treatment plants, however, their efficiency for turbidity removal, which is determined by qualitative indices, has been considered. Current qualitative indices such as turbidity and escaping particle number could not completely measure the efficiency of the filtration system; therefore defining new qualitative indices is essential. In this study, the efficiency of two different dual media filters in turbidity removal was compared in different operating condition using qualitative indices. The pilot consisted of a filter column (1-m depth) in which the filter-1 was consisted of a layer of anthracite (450-mm depth) and a layer of silica sand (350-mm depth); and filter-2 had the same media characteristics except for the first layer that was light expanded clay aggregates (LECA). Turbidities of 10, 20, and 30 NTU, coagulant concentrations of 4, 8, and 12 ppm and filtration rates of 10, 15, and 20 m/h were considered as variables. Results showed that the media of filter-2 is a suitable substitute for the media of filter-1 (P value < 0.05). Turbidity removal efficiencies in different condition were 79.97 ± 1.79 to 91.37 ± 1.23% for the filter-2 and 75.12 ± 2.75 to 86.82 ± 1.3% for the filter-1. The LECA layer efficiency in turbidity removal was independent of filtration rates and due to its low head loss; LECA can be used as a proper medium. Results also showed that the particle index was a suitable index as a substitute for turbidity and escaping particle number as indices.
A small full-scale ozonation/biofiltration plant was operated for 1.5 years in mid-Norway. A three-media biofilter was used to remove biodegradable organic matter from ozonated water. The biofilter contained granular activated carbon (GAC), phonolith and CaCO3 and was operated at 26-30 min. empty bed contact time. The water temperature varied between 2 and 14°C but the biofilter was operated most of the time at temperatures below 10°C. Total phosphorus concentration in the raw water was also very low (1.1-2.0 μg L-1). Batch tests showed that low phosphorus concentration and low temperature are potential limitations for microbial growth and organic carbon removal. Initially, the GAC adsorbed organic carbon while the microbial activity was building up. Most of the adsorption capacity was used after 1.5 months of operation. After this period, 14-33% of the TOC was removed (average 23%). Although the overall TOC removal in the process was modest, average BDOC removal of 55% was observed even at 3°C. Ozonation was effective in reducing colour with average removal of 80%. The results show that significant biological activity can be achieved and maintained in biofilter treating ozonated water even at low temperatures and phosphorus limited conditions.
The removal of biodegradable ozonation byproducts was evaluated at pilot-scale using one conventional biofilter containing sand and anthracite and five fixed bed biofilm reactors (FBBRs) containing plastic media. Four of the FBBRs incorporated chemical or environmental optimization strategies (light restriction, chloramine, hydrogen peroxide, and nutrients) to either promote healthy biomass or minimize macrofauna proliferation. Conventional media biofiltration consistently removed assimilable organic carbon (AOC) by a maximum of 70% and was not susceptible to snail grazing. The control FBBR reduced AOC by a maximum of 60%, but dropped to zero following snail grazing on established biomass. Adenosine triphosphate (ATP) was used to quantify viable biomass attached to plastic media (tATP) and aqueous biomass in the column effluent (cATP). The control FBBR averaged 61 ng tATP/cm3 of attached biomass compared to chloramine (7 ng tATP/cm3), hydrogen peroxide (21 ng tATP/cm3), dark conditions (45 ng tATP/cm3), and nutrients (61 ng tATP/cm3). Hydrogen peroxide (1.8 mg/L) and light restriction strategies precluded dark algae and chironomids, but allowed snail development. None of this biota was observed in the presence of chloramine (0.20 mg/L). While the conventional biofilter and control FBBR produced similar AOC removals, FBBRs were sensitive to hydraulic disruptions and susceptible to grazer organisms.
The removal of biodegradable ozone by-products was evaluated at pilot scale using a fixed-bed biofilm reactor (FBBR) containing spherical plastic support media. Six FBBRs were operated in parallel with varying media sizes (1-, 1.25-, or 2-in, diameter) and empty bed contact times (EBCTs; 6 or 12 min). Influent water was provided from a full-scale water treatment plant following ozonation, coagulation, and flocculation processes. After seven months of operation, pseudosteady-state conditions were achieved with up to 50% removal of assimilable organic carbon (AOC) and up to 40% reduction in ultraviolet absorbance at 254 nm (UV254). Increases in FBBR effluent turbidity and head loss were also indicative of biomass development and sloughing. Process efficiency deteriorated because of the consumption of biomass by snails and other invertebrates.
The moving bed biofilm process is based on plastic carriers on which biomass attaches and grows. The original Kaldnes carrier was made of high- density polyethylene (density 0.95 gcm-1) that could be used in filling fractions (volume of carriers in empty reactor) up to 70% that gives a specific area of 350 m2m-3. Lately there has been an interest in the use of larger carrier elements, especially when using the process for upgrading of activated sludge plants. This paper analyses the influence of the carrier size and shape on performance, especially related to highly loaded plants working on municipal wastewater. The results demonstrate that moving bed biofilm reactors should be designed based on surface area loading rate (g COD/m2d) and that shape and size of the carrier do not seem to be significant as long as the effective surface area is the same. The results indicate that very high organic loads can be used in order to remove soluble COD but that the settleability of the sludge is negatively influenced at high loading rates.
Results from UFC tests will enable direct comparison of DBP formation in different water sources.
A new chlorination approach has been developed for assessing disinfection by‐product (DBP) formation under constant, yet representative conditions. The rationale used in the development of the uniform formation conditions (UFC) test and the results of a parametric sensitivity analysis are presented. Within the acceptable range of conditions, the DBP formation varied by less than 4 percent for the three waters examined. UFC test results will allow a direct comparison of DBP formation among different waters and allow the evaluation of how treatment changes affect DBP formation in a specific water.
Recently developed analytical techniques allow for the quantification of C₁-C₁₀ straight-chain aliphatic aldehydes, benzaldehyde, and the dialdehydes glyoxal and methylglyoxal down to 1 μg/L. These compounds are formed as the partial oxidation products of the reaction between disinfectants (particularly ozone) and naturally occurring organic matter. Various full-scale and pilot treatment plants in North America that employ ozonation were surveyed using these techniques, which showed a trend toward both monoaldehyde and dialdehyde formation. Once formed, aldehydes can persist in the water and their concentrations may even increase following postdisinfection. An effective means of aldehyde removal appears to be the use of biologically active granular activated carbon filters, whose filtration mode determines the actual degree of removal. Dialdehydes require a slower filtration rate for their removal than formaldehyde and acetaldehyde. Técnicas analíticas creadas recientemente permiten la cuantificación de las cadenas lineales de aldehidos alifáticos CiCio, el benzaldehído, y los dialdehídos glyoxiales y metilglioxiales hasta de 1 μg/L. Estos compuestos se forman como productos de oxidación parcial provenientes de la reacción que se produce entre los desinfectantes (en especial el ozono) y la materia orgánica natural. Usando estas técnicas, se investigaron varias plantas de escala normal y escala de planta piloto en norteamérica que emplean la ozonización. Las plantas demostraron una tendencia hacia la formación de monoaldehídos y dialdehídos. Una vez formados, los aldehidos pueden permanecer en el agua, y sus concentraciones pueden aumentar después de la post-desinfección. Los filtros de carbón granular activado que son biológicamente activos parecen ser métodos efectivos para remover los aldehidos, y su medio de filtración determina el grado actual de remoción. Los dialdehídos requieren menores velocidades de filtración que los formaldehídos y los acetaldehídos.
Treatment of hurruc water was studied in a pilot-scale ozonation/biofiltration treatment plant. The raw water had TOC and CODMn concentrations of 3.2–5.0 and 4.1–6.6 mgO l−1, respectively, and colour (410 nm) of 30–50 mgPt l−1. The effect of biofilter loading rate on removal of organic matter and ozonation by-products was investigated in two upflow biofilters containing expanded clay aggregate (Filtralite) media. The empty bed contact times ranged from 11 to 54 min. The TOC removals varied from 18 to 37% and the CODMn removals from 30 to 48% with ozone dosages from 1.0 to 1.7 mgO3 mgTOC−1. The ozone dosage seemed to have larger effect on removal efficiency than the loading rate. Concentrations of aldehydes (sum of formaldehyde, acetaldehyde, glyoxal and methyl glyoxal) were 41–47 μg l−1 in ozonated water. Formaldehyde and glyoxal were the only aldehydes detected from the biofilter effluents at concentrations higher than 1 μg l−1, but their mean concentrations were below 2.1 μg l−1. The ketoacid concentrations (sum of glyoxylic, pyruvic and ketomalonic acids) ranged from 272 to 441 μg l−1. Average biofilter effluent concentrations varied from 5.3 (glyoxylic acid) up to 67 μg l−1 (ketomalonic acid) with steady-state reductions generally over 80%. The aldehydes and ketoacids accounted on average for 16% of the biodegraded TOC. The results show that expanded clay aggregate media is a good alternative as biofilter material.
Identification and quantification of ozonation by-products: keto-acids in drinking water
- Y Xie
- D A Reckhow
Xie, Y. and Reckhow, D.A. (1992). Identification and quantification of ozonation by-products: keto-acids in
drinking water. Paper #5 in The Proceedings of the IOA Pan American Committee, Pasadena
Conference: Ozonation for Drinking Water treatment, March 10-13, 1992.