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Hydrogen Sulphide Control in Municipal Sewers
Abstract
Increased concern for the impact of hydrogen sulphide produced under anaerobic conditions in wastewater has lead to the need for pretreatment of the sewage.
Intensive field investigations on hydrogen sulphide formation, impacts and control in sewerage systems were carried out during the period 1985–1987. Emphasis was given to determining the importance of sulphate, organic matter, temperature and anaerobic residence time on sulphide formation in a 3.9 km pressure main.
Based on these studies an empirical model for the sulphide buildup in sewers was proposed and evaluated. Variation of the diurnal sewerage composition and flow and the importance of the type of sewage (municipal/industrial) on sulphide formation was also taken into account.
Furthermore, full scale experiments in which iron sulphate was added to the sewage were carried out under fluctuating conditions in order to optimize precipitation of the sulphide produced and reduce the impact of the hydrogen sulphide. A system for control and adjustment of the chemicals dosed was developed based on the proposed model and an evaluation of the importance of the external parameters and conditions.
... The generation and emission of hydrogen sulfide has since long been identified as a major cause of corrosion and odor problems in a sewer system [1][2][3][4][5][6]. All detrimental phenomena (malodors, metal corrosion, concrete disintegration, and health hazard) associated with hydrogen sulfide in gravity sewers depend on the rate of H 2 S (g) emission from the aqueous phase to the gas phase of the pipe. ...
... This means, no H 2 S (g) emission will occurr if H 2 S (aq) is not generated. Consequently, the prediction of hydrogen sulfide generation into the sewer aqueous phase is a prerequisite for a better control over sulfide-related problems in sewer collection systems, controlling the sulfide generation from the aqueous phase [5,6]. ...
... A lower pH conducts the reaction toward more H 2 S (aq) production [51]. Equation (5) demonstrates the relationship between the concentration of H 2 S (aq) and pH. ...
In this study, the interactive effects of four independent variables (initial chemical oxygen demand (COD) concentration, rotational velocity, temperature, and retention time) on the sulfide generation process in municipal wastewater were investigated. The process was modeled and analyzed with the variables in a series batch experiments. Experiments were conducted based on a central composite face-centered design and analyzed using response surface methodology. The region of exploration for the process was taken as the area enclosed by COD (250 and 650 mg/L), rotational velocity (40 and 200 rpm), temperature (16 and 28°C), and retention time (2 and 40 h) boundaries. Eleven dependent parameters were either directly measured or calculated as response. The most influential variable on H2S (g) production was found to be retention time. The results showed that simultaneous increase in temperature and rotational velocity caused an increasing trend in the amount of H2S (g) emitted. Total sulfide was decreased by increasing rotational velocity due to more H2S (g) secretion resulting from increased mixing rate. The present study provides valuable information about interrelations of quality and process parameters at different values of the studied variables.
... Severe problems are associated with the microbial reduction of sulfate to sulfides in sewer systems, especially in pressurized flows (Hvitved-Jacobsen et al., 1995). Previous studies on sulfide production in pressure mains have resulted in a number of empirical formulas which are still used in praxis and are based on parameters such as biochemical oxygen demand (BOD), chemical oxygen demand (COD), sulfate concentration and temperature etc. (Thistlethwayte (1972), Boon and Lister (1975), Pomeroy and Parkhurst (1978), Hvitved-Jacobsen et al. (1988), Nielsen et al. (1998)). In this investigation, the mostly used empirical formulas are to be evaluated using statistical analysis to determine the relationships of the key parameters promoting sulfide formation in pressure sewers, especially sulfide production at the biofilm -wastewater interface. ...
Sewer networks are one major pillar of modern cities’ infrastructure. Their functionality
ensures the transport of wastewater to the sewage treatment plant and the transport of rainwater
from residential areas. Damages to sewers cause infiltration and exfiltration and at
the same time high costs for rehabilitation. The formation of hydrogen sulphide (H2S) represents
a risk factor for the conditions of concrete channels. Its emission cannot only cause
the destruction of sewer walls by concrete corrosion, but can also represent a safety risk
for sewer workers. Within the last decades, the characteristics of H2S emissions were intensively
investigated and various models for predicting odour and corrosion were developed.
The current state of the art are one-dimensional model approaches. At the same time, some
predominant processes, e.g. the flow velocities in the air phase, are three-dimensional, and
H2S emissions are very relevant on locations with high turbulence and complex flow fields
(e.g. drops).
This work continues at this point. It investigates and extends a three-dimensional twophase
model with regard to different aspects. For this purpose the two-phase solver interFoam
of the software OpenFOAM is used. Initially, the hydrodynamic properties for
different models in closed conduits are investigated by analysing hydrodynamic properties
for different models in closed cross sections. The analysis begins with the simulation
of a simple single-phase water flow over a ground sill and is then extended to a highly
complex sewer geometry. The complex sewer network geometry is compared with results
of a 1:20 scale model and existing CFD simulations for an open geometry. The results
show a good agreement. Extensions are based on the description of mass transfer using
the Henry coefficient. Furthermore, adjustments are made to improve the specifics of H2S
emissions in sewers. These include the description of the temperature dependency of the
Henry coefficient, the equilibrium between H2S and the bisulphide ion (HS-) in the water
phase and the influence of the pH value on this equilibrium. An additional extension describes
the concentration of H2S in the air phase as partial pressure. The extensions and
adaptations are validated using different analytical examples and the advantages of using a
three-dimensional model over a one-dimensional approach are demonstrated using the example
of the complex sewer geometry. Finally, the extended solver is coupled with a solver
for dynamic geometries to validate the simulated mass transfer under turbulent conditions.
The comparison of simulation results for mass transfer in a stirring tank with different stirring
rates leads to a good agreement with experimental results from laboratory experiments.
This work results in two new solvers, the difference of which lies in the geometry to
be described. The first solver can be applied to static meshes, while the second solver can
describe dynamic meshes, such as rotating geometries.
... Equations (4) and (6) introduce a dimensionless parameter, ε, to account for different wastewater sources, ranging from 0.001, for typical Danish domestic effluents, to 0.01 for effluents resulting from food processing industries with high concentration of biodegradable organic matter. Boon and Lister, 1975 í µí±′í µí°µí µí±í µí°· × 1.07 í µí±−20 (3) Pomeroy and Parkhurst, 1977 í µí¼ 1 × (í µí° ¶í µí±í µí°· − 50) 0.5 × 1.07 í µí±−20 (4) Hvitved Jacobsen et al., 1988 1.52 × 10 −2 í µí° ¶í µí±í µí°· × ( 1 + 0.004í µí°· í µí°· ) Boon, 1995 í µí¼ 2 × (í µí° ¶í µí±í µí°· − 50) 0.5 × 1.03 í µí±−20 (6) Nielsen et al., 1998 Adjusted í µí¼ 1 in Eq. (4) for various Danish effluents (7) Nielsen et al., 1998 0.0025 × 10 −3 í µí° ¶í µí±í µí°· í µí± 2.1 × 1.07 í µí±−20 (8) Elmaleh et al., 1998 Adjusted M' in Eq. (3) (9) Hvitved-Jacobsen, 2002 Table 1-Summary of models to forecast sulfide build-up in wastewater rising mains ...
Abstract Production and build-up of sulfide in wastewater systems, especially downstream of rising mains, may lead to severe odour nuisance, toxic environments and high risk of corrosion. Due to increased population migration towards cities and lower area availability for treatment facilities, rising mains for the conveyance of wastewater sludge are becoming more frequent, and research on sulfide build-up in such cases is needed. In this paper the findings of the work carried out in a full scale wastewater sludge rising main, operated during different seasons and under distinct conditions are presented (comprising both the start-up and normal operation stages of the facility). Results showed a sulfide build-up rate of 3.24 g S−2 m−2 d−1 in the summer and of 2.30 g S−2 m−2 d−1 during the winter. The ratio of sulfate reduction to sulfide production (SO4−2/S−2) was of roughly 3 to 1, as expected. Furthermore, obtained results allowed adjusting a second order polynomial empirical equation for the forecasting of sulfide build-up within the sludge rising main. The obtained equation for sludge significantly differs from existing equations obtained for wastewater. Moreover, this work also allowed obtaining new insight into the positive influence of biofilm and hydraulic retention time in the biological sulfide generation, as well as into its variation along the length of the rising main.
... Τα τελευταία χρόνια έχουν διατυπωθεί αρκετές εμπειρικές εξισώσεις για την εκτίμηση της ποσότητας υδροθείου που παράγεται σε αγωγούς ακαθάρτων (βλ. WPCF & ASCE, 1976, ATV, 1982β, von Bielecki & Schremmer, 1987, Hvitved-Jacobsen et al., 1988. Από αυτές δίνονται παρακάτω οι πιο εύχρηστες και διαδεδομένες, που για λόγους ομοιομορφίας έχουν αναχθεί στις ίδιες μονάδες του SI. ...
Το βιβλίο καλύπτει θέματα σχεδιασμού και λειτουργικού ελέγχου των δικτύων αποχέτευσης. Περιλαμβάνει στοιχεία από την ελληνική τεχνολογική εμπειρία στα αποχετευτικά έργα (μεθοδολογίες και προδιαγραφές) με παράλληλη αναφορά σε στοιχεία της διεθνούς βιβλιογραφίας. Δίνει έμφαση στις επιστημονικές αρχές που αιτιολογούν τις προδιαγραφές και τις μεθοδολογίες. Επίσης, ενσωματώνει και ορισμένα πρωτότυπα στοιχεία. Αποτελείται από οκτώ κεφάλαια. Στο πρώτο δίνονται οι βασικές έννοιες και οι ορισμοί μαζί με ένα σύντομο ιστορικό και μια γενική περιγραφή των μελετών αποχέτευσης. Στο δεύτερο κεφάλαιο αναφέρονται οι μέθοδοι εκτίμησης των παροχών ακαθάρτων, με παράθεση χρήσιμων δεδομένων, ελληνικών και διεθνών. Στο τρίτο κεφάλαιο δίνεται η τυπική μεθοδολογία εκτίμησης των παροχών ομβρίων, με ιδιαίτερη αναφορά στις ελληνικές συνθήκες (παράθεση τυπικών όμβριων καμπυλών, κτλ.). Το τέταρτο κεφάλαιο καλύπτει τους υδραυλικούς υπολογισμούς που είναι απαραίτητοι για το σχεδιασμό, τον έλεγχο επάρκειας και την εκτίμηση των χαρακτηριστικών ροής των αγωγών αποχέτευσης. Έμφαση δίνεται στην αντιμετώπιση ορισμένων μη τυπικών καταστάσεων λειτουργίας των αγωγών (πχ. πολύ μεγάλες ή πολύ μικρές κλίσεις και ταχύτητες), οι οποίες μπορεί να προκαλέσουν σοβαρά προβλήματα στη λειτουργία των δικτύων. Στο πέμπτο κεφάλαιο παρουσιάζονται οι πιο σύγχρονες αντιλήψεις και υπολογιστικές μέθοδοι των αποχετευτικών δικτύων που βασίζονται στην συνολική προσομοίωση της λειτουργίας τους (υδρολογική και υδραυλική). Το έκτο κεφάλαιο καλύπτει ορισμένα ποιοτικά θέματα τα οποία συναρτώνται με το σχεδιασμό και τον έλεγχο της λειτουργίας των δικτύων, όπως είναι η παραγωγή και απελευθέρωση υδροθείου στους αγωγούς και οι συνέπειές της. Στο έβδομο κεφάλαιο περιλαμβάνονται τεχνολογικά θέματα, όπως η επιλογή υλικών για τους προκατασκευασμένους σωλήνες, ο τρόπος κατασκευής των χυτών επί τόπου αγωγών και η αντιδιαβρωτική προστασία των αγωγών λυμάτων. Τέλος, στο όγδοο κεφάλαιο δίνονται πληροφορίες για κάποια εναλλακτικά συστήματα αποχέτευσης. Μερικές από τις πρωτότυπες αναλύσεις που περιλαμβάνονται στο βιβλίο είναι: (α) η στατιστική θεμελίωση και μοντελοποίηση της διακύμανσης των παροχών ακαθάρτων, (β) η κατάρτιση αλγορίθμων αριθμητικής επίλυσης διάφορων υδραυλικών προβλημάτων, (γ) η εξαγωγή αναλυτικών σχέσεων που μπορούν να αντικαταστήσουν διάφορα εμπειρικά νομογραφήματα ή πίνακες της βιβλιογραφίας (π.χ. εξίσωση μεταβολής της τραχύτητας συναρτήσει του αδιαστατοποιημένου βάθους ροής σε κυκλικούς αγωγούς, αντίστοιχη εξίσωση για τον άμεσο προσεγγιστικό υπολογισμό του κρίσιμου βάθους σε κυκλικούς αγωγούς, εξίσωση εκτίμησης του συντελεστή τοπικών απωλειών σε συμβολές αποχετευτικών αγωγών), και (δ) η συστηματοποίηση και μεταφορά στο σύστημα μονάδων SI διάφορων εμπειρικών εξισώσεων της βιβλιογραφίας (π.χ. εξισώσεις εκτίμησης χρόνων συρροής ομβρίων, εξισώσεις παραγωγής υδροθείου, κ.ά.).
... Significant physical factors are temperature, flow velocity, wastewater retention time and the surface area inside the pipe where slim layer is formed [2,3]. The highest rate of sulphide formation is found to be within the pH range of 6.0 to 8.5 [4,5]. ...
The objective of this work was to study the sulphide, especially the dihydrogen sulphide formation process in sewage pressure pipes and the influence of sulphur rich wastewater on oxygen consumption of activated sludge of Kohtla-Järve wastewater treatment plant (WWTP). In this work the equilibrium distribution between three different forms of sulphide was investigated by changing pH of the wastewater and Na2S solutions in the closed vessel. At the same time the content of H2S in the gas phase was measured. To estimate the influence of H2S on the aerobic microorganisms of activated sludge, the ISO 8192 standard test of inhibition of oxygen consumption by activated sludge has been used. At the same time, other inflows of Kohtla-Järve WWTP have been investigated. The leachate from semicoke and ash heaps, rich in sulphates and sulphides (pH 10-12) did not cause any significant inhibition of oxygen consumption of activated sludge microorganisms. The wastewater from oil shale chemical industry containing sulphates and sulphides (pH around 6-6.5), and also gross inflow of Kohtla-Järve WWTP, cause inhibition of oxygen consumption of activated sludge.
... Such equations are referred to in Hvitved-Jacobsen (2002) primarily based on the original and more detailed information in e.g. Thistlethwayte (1972), Boon and Lister (1975), Pomeroy and Parkhurst (1977), Jacobsen et al. (1988), Matos (1992) and Nielsen et al. (1998). Until recently, only empirical models for the prediction of sulfide in sewer networks have been available and only for prediction of sulfide in the water phase. ...
... A number of simple empirical equations have been developed to predict sulfide formation and occurrence in both pressure mains and gravity sewers. Such equations are referred to in Hvitved-Jacobsen (2002) primarily based on the original and more detailed information in Thistlethwayte (1972), Boon and Lister (1975), Pomeroy and Parkhurst (1977), Hvitved-Jacobsen et al. (1988), Matos (1992) and Nielsen et al. (1998). ...
... Hvitved-Jacobsen et al. [15] proposed a parametric equation predicting the sulfide generation in the collection pipes as a function of the soluble COD and residence time that includes a typical proportionality factor for temperature dependence as follows: ...
Two biotrickling filters were set up at two wastewater treatment plants (WWTP) in The Netherlands to investigate their effectiveness for treatment of odorous waste gases from different sources. One biotrickling filter was installed at Nieuwe Waterweg WWTP in Hook of Holland to study the hydrogen sulfide removal from headworks waste air. The other reactor was installed at Harnaschpolder WWTP (treating wastewater of the city of The Hague) to remove mercaptans and other organic compounds (odor) coming from the emissions of the anaerobic tanks of the biological nutrient removal (BNR) activated sludge. The performance of both units showed a stable and highly efficient operation under seasonal variations of load and temperature over nearly one year of monitoring. The Nieuwe Waterweg unit achieved removals of up to 99%, corresponding to a maximum daily average elimination capacity (EC) of 55.8 g H(2)S/m(3)/h at an empty bed residence time (EBRT) as short as 8.5 s. Odor reduction at the Harnaschpolder unit was 95% at an EBRT of 18.9 s, with average outlet concentration lower than the objective value which was established as 1000 European Odor Units (OU(E)/m(3)).
... Fundamental pro cesses related to the sulfur cycle in sewer networks as depicted in Figure 1 are (1) formation of sulfide in sediments and biofilms; (2) emission of H2S(aq) at the air-water interface; (3) chemical and biological oxidation of sulfide in the biofilms, sediments, and water phase; (4) adsorption and consecutive biological oxidation of H2S(g) at sewer surfaces exposed to the sewer atmosphere; and (5) precipitation of sulfide in the water phase. Among these processes, only sulfide formation in the biofilms of pressure mains and gravity sewers has been comprehensively studied (Boon and Lister, 1975; Hvitved-Jacobsen et al., 1988; Nielsen et al., 1998; Pomeroy and Parkhurst, 1977; Thistlethwayte, 1972 ...
The emissions process of hydrogen sulfide was studied to quantify air-water transfer of hydrogen sulfide in sewer networks. Hydrogen sulfide transfer across the air-water interface was investigated at different turbulence levels (expressed in terms of the Froude number) and pH using batch experiments. By means of the overall mass-transfer coefficient (KLa), the transfer coefficient of hydrogen sulfide (KLa(H2S)), referring to total sulfide, was correlated to that of oxygen (KLa(O2)) (i.e., the reaeration coefficient). Results demonstrate that both turbulence and pH in the water phase play a significant role for KLa(H2S). An exponential expression is a suitable representation for the relationship between KLa(H2S) and the Froude number at all pH values studied (4.5 to 8.0). Because of the dissociation of hydrogen sulfide. KLa(H2S) increased with decreasing pH at a constant turbulence level. Relative differences in KLa(H2S) at pH values between 4.5 and 8.0 became larger as the turbulence level increased, whereas those at pH between 4.5 and 7.0 did not statistically show any change. At constant pH, KLa(H2S)/KLa(O2) was observed not to be dependent on the turbulence range studied. KLa(H2S)/ KLa(O2) ratio was 0.86, with a 95% confidence interval of 0.08 at low pH, where only molecular hydrogen sulfide was present. This ratio was found to be equal to the ratio between the diffusion coefficient of hydrogen sulfide and that of oxygen. which was determined by empirical equations proposed in the literature. This fact was observed at all the turbulence levels investigated. Based on the findings in this study, an empirical equation describing the pH dependence of KLa(H2S)/KLa(O2) at a pH range of 4.5 to 8.0 is proposed. Theoretical and experimental aspects of hydrogen sulfide emissions and an application are discussed related to in-sewer conditions.
The corrosion and odor in concrete sewers are mainly related to the sulfide production, which is, under certain circumstances, directly proportional to the hydraulic retention time (HRT) of the sewer. To reduce the corrosion and control the odor in concrete sewers, it is necessary to model the production of sulfide in the concrete sewers with different HRTs. However, previous researches were mostly carried out in simulated Perspex-made sewers, and the obtained theoretical formulas based on the Monod equation were impractical because of the complexity. An actual concrete pipe with domestic sewage was employed in this study to obtain a simple but practical model, which can be applied to quantitively describe the sulfide production according to the HRT of the sewer and the chemical oxygen demand (COD) of the sewage. The empirical equation obtained was , the coefficient is a logarithmic function of the HRT, and the sulfide production rate and COD have a power relationship. Based on the data of COD and HRT obtained in the realistic sewer, the production of sulfide in the sewer can be predicted for better maintaining sewers through sulfide control. HIGHLIGHTS
An actual concrete pipe was used to evaluate the effect of HRT on the variation of pollutants.;
Few degradations of nitrogen and phosphorus in an actual concrete pipe were found with HRT.;
The degradation of COD in an actual concrete pipe accorded with the first-order reaction law.;
Sulfide production rate was the power function of solute COD, and the coefficient is the logarithmic function of the HRT.;
The aim of the research was to determine changes in the elemental composition of concrete under the influence of exposure to hydrogen sulphide in the existing sewage system. The system operator pointed to significant problems with odours in this system. The research included a fragment of the pressure sewage system. The concentration of gases: hydrogen sulphide, ammonia and methane was measured in selected wells. High concentrations of hydrogen sulphide (over 200 ppm) were recorded in the studies. Concrete samples were taken from the internal walls of the well for testing. The samples were used for a microscopic analysis of their composition, using an electron microscope with an EDS attachment. Also, concrete samples from a new sewage well were tested to compare their elemental composition. Gas measurements confirmed the problem of odors, while the analysis of the elemental composition showed a significant proportion of sulphur (from 7.53% to 42.9%) on the surface of the well compared to the reference sample (0%).
The problems related to hydrogen sulfide in terms of deterioration of sewer networks, toxicity and odor nuisance have become very clear to the network stakeholders and the public. The hydraulic and (bio)chemical phenomena and parameters controlling sulfide formation, emission and their incidences in sewer networks are very complex. Recent research studies have been developed in gravity and pressure sewers and some transfermodels have been published. Nevertheless, themodels do not take into account all the physical phenomena influencing the emission process. After summing up the main scientific knowledge concerning the production, oxidation, transfer and emission processes, the present review includes: (i) a synthetic analysis of sulfide and hydrogen sulfide emission models in sewer networks, (ii) an estimation of their limit, (iii) perspectives to improve the modelling approach. It shows that sulfide formation and uptake models still need refinements especially for somephenomena such as liquid to gasmass transfer. Transfermodels that have been published so far are purposely simplified and valid for simple systems. More efforts have to be undertaken in order to better understand the mechanisms and the dynamics of hydrogen sulfide production and emission in real conditions.
An empirical model for predicting sulfide production in pressure mains (Hvitved-Jacobsen et al., 1988) was evaluated and modified based on results obtained from two intercepting pressure mains located in the Northern part of Jutland, Denmark. Mass balances in pipe influent and effluent were made for volatile fatty acids, VFA (formate, acetate, propionate and butyrate), dissolved COD, DOC and sulfide and biofilm surface rate for sulfide and organic matter were calculated. Relatively high sulfide formation rates were observed at low temperatures (5–12°C). The sulfide production rate strongly depended on wastewater quality in terms of VFA and dissolved carbohydrate concentration. Based on these two sets of observations — wastewater quality and temperature — the original empirical model was modified.
During treated wastewater transport, phenomena related to the presence or absence of dissolved oxygen (DO) have been observed. In Tenerife reclaimed urban wastewater (RUWW) transport from the capital, Santa Cruz to the south of the island for agriculture reuse was studied. Anoxic conditions and H2S generation were noted during transport. As RUWW has an electrical conductivity (EC) of about 1600 μS/cm, BALTEN decided to add fresh water (FW) with low EC, saturated or over saturated in DO at an intermediate point in the pipe to reduce the conductivity of water supplied to agriculture, also thus reducing the organic load and consequently H2S generation. However, injection of DO over-saturated fresh water brought on the appearance of nitrification and later denitrification. A study was carried out of H2S generation, nitrification and denitrification during RUWW transport with and without added FW.
The present study has been carried out in a completely filled gravity pipe, 61 km long, which transports reclaimed urban wastewater (RTJWW), for crop irrigation in the island of Tenerife (Spain), at an average water velocity of 0.4 m/s. Due to the long residence time of the reclaimed wastewater in the pipe (40 hours), anaerobic conditions usually appear, and chemical transformation of reclaimed wastewater occurs during transportation, especially sulfide generation. Field studies have been conducted from November 1994 to January 1997. The variation in sulfide and oxidation-reduction potential (ORP) among other parameters during wastewater transportation have been reported. The object of this work is to study the kinetics of the sulfide generation in a full scale reclaimed wastewater pipe, in order to obtain a forecasting equation of sulfide generation, and to compare this equation with those previously proposed for raw wastewater sewers. Equations obtained from this research differ quite from those previously proposed for sewers. This can be due to the reclaimed wastewater used in this system, which has a very much lower organic matter content than raw wastewater.
The kinetics and stoichiometry of Desulfovibrio desulfuricans attached to a polycarbonate surface were determined in RotoTorque™ reactors and compared with those of suspended cells. Biofilm specific cellular growth rate (μb) and detachment rate (qdx) were determined from unsteady state biofilm experiments. In the initial biofilm accumulation phase, the specific cellular growth rate was the same as the maximum specific growth rate for D. desulfuricans in suspension (μmax = 0.37‐h); thereafter μb decreased and approached a steady state value of about 0.1‐h. The decrease in average cellular specific growth rate could be attributed to substrate (lactate) limitation in some experiments, but in others there was no evidence of this. Biofilm‐specific cellular detachment rate decreased similarly to biofilm‐specific cellular growth rate. In biofilms, cellular yield at μb= 0.1.h was approximately 18% of planktonic cellular yield partly due to the production of extensive extracellular polymeric substance. A linear relationship between μb and specific lactate utilization rate (qs) in the biofilm did not exist. During the steady state biofilm accumulation phase (μb =.0.1.h), specific lactate utilization by biofilm cells was about 2–3 times greater than by planktonic cells, whereas it was essentially the same during the initial biofilm accumulation phase. These results suggest that kinetic and stoichiometric data derived from suspended cells must be cautiously incorporated into biofilm accumulation models.
Transport of wastewater in sewer networks causes potential problems associated with hydrogen sulfide in regard to odor nuisance, health risk, and microbially induced corrosion. To what extent these problems occur depends not only on the rate of sulfide formation but also on the rate of hydrogen sulfide emission into the sewer atmosphere. To gain understanding of the influence of wastewater constituents on the emission process, a number of batch experiments were conducted on domestic wastewater collected from sewer networks. The emission rate of hydrogen sulfide in the wastewater investigated was found to be approximately 60% of that in de-ionized water in terms of the overall mass-transfer coefficient, resulting in a correction factor (alpha) of 0.6. The alpha factor did not change significantly within the turbulence range studied (Froude numbers of 0.04-0.23). The Henry's law constant for hydrogen sulfide in wastewater was observed to be close to that in de-ionized water, reflecting a correction factor (beta) of 1.0. By taking these results into account, modeling aspects of hydrogen sulfide emission in sewer networks are presented in this paper.
New equipment and procedures for chemical and microbiological tests, simulating biogenic sulfuric acid corrosion in sewerage systems, are presented. Subsequent steps of immersion and drying, combined with mechanical abrasion, were applied to simulate events occurring in sewer systems. Both chemical and microbiological tests showed that the aggregate type had the largest effect on degradation. Concrete with limestone aggregates showed a smaller degradation depth than did the concrete with inert aggregates. The limestone aggregates locally created a buffering environment, protecting the cement paste. This was confirmed by microscopic analysis of the eroded surfaces. The production method of concrete pipes influenced durability through its effect on W/C ratio and water absorption values. In the microbiological tests, HSR Portland cement concrete performed slightly better than did the slag cement concrete. A possible explanation can be a more rapid colonisation by microorganisms of the surface of slag cement samples. A new method for degradation prediction was suggested based on the parameters alkalinity and water absorption (as a measure for concrete porosity).
Over the past decade, considerable investment has been made in acquiring knowledge about in-sewer processes, with the objective of developing new analytical tools to predict the performance of these systems. A wide variety of these tools have emerged, from simple aggregated conceptual models of entire systems, to very detailed physically based relationships for particular processes such as suspended transport. The major investors in this research have been determined to produce commercial models which will form part of integrated system analysis suites of software for use in the formulation of holistic and optimum managerial methods for wastewater systems. Unfortunately, sewer processes are extremely complex, and the very limited investment, when compared proportionately with that made in hydrological and hydraulic analysis over previous decades, has produced apparently detailed empirical/physically based deterministic models for which there are a number of important outstanding gaps in underlying knowledge which are not generally acknowledged. This paper reviews the current position with regard to sewer process modelling, highlighting areas where knowledge is still deficient, and where new opportunities and limitations are emerging.
The present work is part of an experimental study carried out in a completely filled gravity pipe, 61 km long, which transports reclaimed urban wastewater (RUWW), for crop irrigation with an average water residence time of 42 h, in the island of Tenerife (Spain). Field studies were conducted from November 1994 to June 1995. H2S generation has been observed in the pipe when anaerobic conditions appear. A direct relation between sulfide generation and the organic matter measured as COD has been seen. S(II) build-up in this pipe is compared with the predicted S(II) according to equations proposed by Boon and Lister (1975), Hvitved-Jacobsen et al. (1988) and Boon (1995) for sewers [Boon, A. G. and Lister, A. R. (1975) Formation of sulphide in rising main sewers and its prevention by injection of oxygen. Prog. Water Technol. 7(2), 289–300; Hvitved-Jacobsen, T., Juette, P. H., Nielsen, P. H. and Jensen, N.Aa. (1988) Hydrogen sulphide control in municipal sewers. In Pretreat. in Chem. Wat. and Wast. Treat., Proceedings of the 3rd International Gothenburg Symposium, eds. H. H. Hahn and R. Klute, pp. 239–247. Springer Verlag, Gothenburg, Sweden; Boon, A. G. (1995) Septicity in sewers: causes, consequences and containment. Water Sci. Technol. 31(7), 237–253.]. Changes in oxidation–reduction potential (ORP) during transportation are presented and an empirical equation which relates S(II) concentration in wastewater with the oxidation–reduction potential (ORP) and sulfate has been developed.
Sewers systems are dynamic in nature, with periodic variation of hydraulic flow and wastewater substrate concentrations. While various models are currently available for predicting hydrogen sulfide (H2S) production in rising mains, they assume constant biofilm activities along the length and ignore the effect of substrate availability on biofilm development. To investigate variation in rising main biofilm structure and activity, detailed studies were carried out on a Robbins device setup, which was established in parallel to a real rising main that it simulated. The changes in wastewater characteristics, as wastewater traveled through both the experimental setup and the real sewer system, were monitored. The study revealed that the biofilm activities varied significantly with locations, with biofilm corresponding to the start of the rising main capable of greater sulfide and volatile fatty acid production than biofilm downstream. Analysis of microbial community composition of these biofilms showed a difference in diversity and abundance, both with regard to general bacterial populations and sulfate reducers. These differences were hypothesized to be a consequence of varying substrate types and availability along the sewer line. The results suggest that the biofilm structure and activity may vary considerably along the length of rising mains and should be taken into consideration for improved sewer modeling and when considering the overall effect of different hydrogen sulfide management options.
The agricultural reuse of reclaimed wastewater has become a necessity in places with water shortages. Frequently, this involves the operation of long transportation pipelines, like in the South Tenerife reuse system, whose main element is a completely filled 61 km long gravity pipe in cast iron. Sulphide generation, which could contribute to pipe corrosion, is a usual process taking place during transportation if anaerobic conditions prevail. In the Wastewater Treatment Plant of Santa Cruz (Tenerife, Spain) a partial nitrification process was achieved by increasing the mean residence time through the aeration step at low dissolved oxygen concentration. Such conditions, combined with the right temperature and a free ammonia concentration above 1 mg l(-1), inhibited nitratation and favoured nitritation, which led to concentrations of NO2-N above 8 mg l(-1) in the secondary effluent. During the transportation, nitrite inhibited the appearance of anaerobic conditions, and, consequently, no sulphide generation occurred. At the same time, a nitrite reduction process took place with a first order kinetics and a rate coefficient of 0.052 h(-1)' at 25 degrees C. A parallel behaviour between the nitrite depletion and the oxidation-reduction potential evolution along the pipeline was also observed.
Thiothrix from activated sludge is, in the presence of oxygen, able to oxidize sulfide and thiosulfate and store many clear sulfur granules at sulfide concentrations less than about 1 mM and thiosulfate concentrations of 0.1-20 mM. On this basis, a sulfur storage test for the identification of Thiothrix in activated sludge was developed. It is shown that the filamentous bacteria, Type 021N (commonly causing bulking in sewage plants), is able to store sulfur granules and thus is a Thiothrix. In enrichment cultures with thiosulfate typical Thiothrix rosettes and motile gonidia are developed, and the presence of a sheath is demonstrated. Filamental diameter varies between 0.8-2.4 μm, the youngest filaments being thinnest. Attempts to isolate Thiothrix have been unsuccesful, but Thiothrix filaments with only a few contaminants are able to grow on solid media with acetate as the only carbon and energy source, indicating the presence of heterotrophic strains. The filamentous organisms of 14 Danish sewage treatment plants are identified, Thiothrix being the most common in 8, and responsible for bulking in 4 plants.
This paper describes a theoretical and experimental approach to evaluating nitrification inhibition (types and degrees) by some substances to be found in coke plant discharges.
The Problem of Hydrogen Sulphide in Sewers
- R D Pomeroy
The Problem of Hydrogen Sulphide in Sewers. Clay Pipe Development Association Ltd
- R D Pomeroy
- RD Pomeroy