bluuebunny/crossref_metadata_2025 huggingface dataset:
Reuse of Textile Reactive Azo Dyebaths Following Biological Decolorization
Authors: Lee Young H. , Pavlostathis Spyros G.
Published: September 2006

The objective of this work was to evaluate the feasibility of biological decolorization and reuse of textile reactive azo dyebaths with the goal of developing an in–plant, closed–loop decolorization system leading to water conservation and wastewater minimization. Decolorization of three spent dyebaths was investigated using a suspended–growth, halophilic mixed culture under anoxic conditions. A high rate and extent of color removal ranging from 77 to 90% was achieved. The three azo dyebaths and their decolorization products did not inhibit the halophilic culture. Although single dyeings using the biologically renovated dyebaths as process water resulted in highly reproducible and consistent fabric color shades, pH adjustment of the renovated dyebaths during the dyeing cycle was necessary. The extent of color removal using a biofilm reactor ranged from 86 to 95% during five repetitive dyebath decolorization and reuse cycles without any inhibition and residual color buildup. Repetitive dyeing with the same biologically decolorized dyebath for up to five cycles using a biofilm reactor and dyebath pH adjustment during the redyeing process resulted in almost identical fabric color shades as standard dyeing using fresh water. Excellent reproducibility in fabric color shades was also obtained by using biologically decolorized dyebaths in cross dyeings with different dyeing recipes. To our knowledge, this is the first report on the feasibility of biological decolorization of spent reactive dyebaths using a halophilic mixed culture and the direct reuse of the renovated dyebath as process water in the dyeing process. The results of this study demonstrate that in–plant application of closed–loop dyeing and decolorization is feasible and has the potential to not only decrease wastewater volume and treatment cost, but also minimize water use as well as the discharge of textile pollutants such as salt and dyes.
Effects of Sample Holding Time on Concentrations of Microorganisms in Water Samples
Authors: Selvakumar Ariamalar , Borst Michael , Boner Mark , Mallon Phil
Published: September 2006

This research investigated the effects of extending the holding time of samples for microbial analysis beyond the standard of 24 hours for purposes such as watershed characterization. Experiments were conducted with both sanitary wastewater and stormwater samples. The refrigerated samples (4 °C) were held for up to 9 days before being analyzed for two pathogens (Pseudomonas aeruginosa and Staphylococcus aureus) and five indicator organisms (total coliform, fecal coliform, fecal streptococcus, enterococcus, and Escherichia coli) by membrane filtration. The concentrations (as colony–forming units per 100 mL) were normalized by log10 transformation and used in subsequent statistical analysis testing for significant differences. The results suggested that the concentrations of microorganisms in water samples analyzed on days 1 and 2 did not vary significantly in 8 of 13 analyses. The results of a field study concluded that the concentration of fecal coliform did not change significantly between 7 hours holding time and greater than 24 hours holding time for fecal coliform.
The Effect of Sodium Chloride on the Two–Step Kinetics of the Nitrifying Process
Authors: Sánchez Omar , Aspé Estrella , Martí María C. , Roeckel Marlene
Published: September 2006

Sodium chloride affects the transformation rate of several compounds in bioreactors. Most authors report a decrease in microorganism activity at increasing salt concentrations. In this work, a kinetic model that relates sodium chloride concentration with the rates of each step of the nitrification process is proposed; thus, the effect of sodium chloride concentration (0 to 60 g/L) on the nitritation and nitratation rates was separately studied. To carry out the independent study of each step, a combination of the respirometric method with sodium azide, an inhibitor of the nitratation step, was performed. The dot–blot hybridization technique with 16S rRNA–targeted probes was used to determine the ammoniaoxidizing and nitrite–oxidizing bacterial fraction, then it was possible to relate the culture's function with its biological composition. Rates of both steps were linearly reduced at increasing salt concentrations; the nitratation rate was more affected than the nitritation rate. Simulations carried out in a nitrifying sequencing batch reactor indicate that nitrite might accumulate at high salt concentrations. Sodium chloride exerts a reversible inhibition on ammonia oxidation and nitrite oxidation.
Air–Water Transfer of Hydrogen Sulfide: An Approach for Application in Sewer Networks
Authors: Yongsiri Chaturong , Vollertsen Jes , Rasmussen Michael , Hvitved–Jacobsen Thorkild
Published: September 2006

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 (KLaH2S), referring to total sulfide, was correlated to that of oxygen (KLaO2) (i.e., the reaeration coefficient). Results demonstrate that both turbulence and pH in the water phase play a significant role for KLaH2S. An exponential expression is a suitable representation for the relationship between KLaH2S and the Froude number at all pH values studied (4.5 to 8.0). Because of the dissociation of hydrogen sulfide, KLaH2S increased with decreasing pH at a constant turbulence level. Relative differences in KLaH2S 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, KLaH2S/KLaO2 was observed not to be dependent on the turbulence range studied. KLaH2S/KLaO2 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 KLaH2S/KLaO2 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 Occurrence of Cyanide Formation in Six Full‐Scale Publicly Owned Treatment Works
Authors: Zheng Anping , Dzombak David A. , Luthy Richard G. , Kavanaugh Michael C. , Deeb Rula A.
Published: September 2006

This paper presents results from an intensive monitoring program implemented at six full‐scale publicly owned treatment works (POTWs) to investigate the fate and formation of cyanide in wastewater treatment processes, with a focus on chlorination and dechlorination processes. A review of historical monitoring data for cyanide species in these POTWs was also conducted. This POTW monitoring program provided a database for the investigation of cyanide formation in wastewater secondary treatment. Data from participating POTWs showed evidence of cyanide formation in this 1‐year monitoring effort, although the cyanide formation pattern varied significantly from one plant to another and among seasons. Generally, the chlorination of thiocyanate (SCN) seems to be the most important mechanism for the formation of cyanide in wastewater treatment processes, especially in chlorination and dechlorination. This hypothesis is supported by the findings of a related laboratory study of mechanisms of cyanide formation in POTWs. It is recommended that POTWs monitor SCN− in influent and secondary effluent to identify its presence and adjust chlorine dose appropriately.
Formation of Free Cyanide and Cyanogen Chloride from Chloramination of Publicly Owned Treatment Works Secondary Effluent: Laboratory Study with Model Compounds
Authors: Zheng Anping , Dzombak David A. , Luthy Richard G.
Published: September 2006

The potential generation of cyanide species in wastewater upon chlorination in the presence of residual ammonia (resulting in chloramine formation) was investigated in experiments with synthetic solutions and publicly owned treatment works (POTW) secondary effluent. This study demonstrated that low concentrations (approximately 5 to 25 μg/L as cyanide) of cyanogen chloride (CNCl), a highly toxic cyanide species not measured in total or free cyanide analyses, could be detected as a result of chloramination reactions in POTW secondary effluent. The potential for chloramination of nitrogen‐bearing organic compounds to yield CNCl and/or free cyanide was demonstrated in experiments with synthetic solutions spiked with selected precursor organics: L‐serine, benzene, catechin, and humic acid. The amino acid L‐serine yielded the largest concentrations of CNCl upon chloramination. Additionally, detectable cyanide (approximately 10 μ/L) was observed in solutions of L‐serine and in POTW secondary effluent that was chloraminated followed by dechlorination to prevent destruction of any free cyanide produced. Thus, chlorination of POTW secondary effluent containing residual ammonia can lead to chloramination of organic compounds and the resulting production of CNCl and free cyanide.
Water‐Extractable Phosphorus in Biosolids: Implications for Land‐Based Recycling
Authors: Brandt R.C. , Elliott H.A. , O'Connor G.A.
Published: September 2006

Phosphorus‐based nutrient management will inevitably be required for land application of biosolids. Water‐extractable phosphorus (WEP) in livestock manures is an indicator of phosphorus loss from agricultural watersheds and this study evaluated its use for biosolids. The WEP to total phosphorus percentage (PWEP) in 41 biosolids (representing a variety of wastewater and solids treatment processes) was compared to dairy and poultry manures and triple superphosphate fertilizer. The mean PWEP for conventionally treated and stabilized biosolids was 2.4%, which was significantly lower than inorganic fertilizer (85%), dairy manure (52%), and poultry manure (21%). Low biosolids PWEP is attributed to elevated aluminum and iron content from chemical additions during wastewater treatment and solids dewatering operations. Facilities using biological phosphorus removal had the highest mean biosolids PWEP (∼ 14%), whereas heat‐dried biosolids had the lowest average PWEP (< ∼ 0.5%). Paired samples of digested cake and the corresponding biosolids treated by processes to further reduce pathogens (i.e., thermal treatment, composting, and advanced alkaline stabilization) showed that these processes tended to reduce biosolids PWEP. Biosolids composition and processing mode exert a controlling influence on the potential for off‐site phosphorus migration at land‐application sites. Nutrient management policies for land‐based recycling should account for the widely varying potential of organic amendments to cause soluble phosphorus losses in runoff and leaching.
Characteristics of Biotic and Abiotic Removals of Dissolved Organic Carbon in Wastewater Effluents Using Soil Batch Reactors
Authors: Cha Woosuk , Fox Peter , Mir Fahad N. , Choi Heechul
Published: September 2006

Biodegradable dissolved organic carbon (BDOC) analyses and abiotic adsorption of dissolved organic carbon (DOC) from different wastewater effluent were conducted to evaluate biotic and abiotic removal mechanisms as a function of the initial DOC concentration and source of DOC using soil batch reactors. To obtain high DOC concentrations, a laboratoryscale reverse osmosis unit was used.  It was found that BDOC fraction was independent of the initial DOC concentration and was dependent on the source of wastewater and/or the types of wastewater treatment. The BDOC fractions varied from 9 to 73%. Trickling filter effluent (Tucson, Arizona) showed the highest BDOC, ranging from 65 to 73% biodegradable, while wastewater treated by the soil aquifer treatment (SAT) (NW‐4) was found to be most refractory, with DOC removals of 9 to 14%. For nitrified/denitrified tertiary effluent (Mesa, Arizona) and secondary effluent (Scottsdale, Arizona), 36 to 42% removal of DOC was observed during the BDOC test. The amount of BDOC in the wastewater depended not on the concentration of DOC, but on the effectiveness of pretreatment. Abiotic adsorption capacity of wastewater effluent varied from 6 to 18%. Molecular weight distribution analyses showed that more than 50% of DOC in the Scottsdale concentrate had a molecular weight of less than 1000 Da, and no significant change in distribution profiles occurred after approximately 12% abiotic adsorption with both soils with acclimated microorganisms (SAT soil) and soils without acclimated microorganisms (non‐SAT soils). Hence, preferential adsorption was not observed and the presence of acclimated microbes did not influence adsorption.
Phase Distribution of Hexachlorobenzene in a Suspended‐Growth Culture Amended with a Polysorbate Surfactant
Authors: Yeh Daniel H. , Pavlostathis Spyros G.
Published: September 2006

The effect of a non‐ionic surfactant on the phase distribution of hexachlorobenzene (HCB) in a suspended‐growth culture system was assessed. Tween 60, a polyoxyethylene sorbitan stearate ester surfactant, and an azide‐inactivated, mixed, methanogenic, HCB‐dechlorinating culture were used in this work. The sorption of HCB on the biomass as well as sorption and aggregation/precipitation of Tween 60 were experimentally quantified. The values of the HCB and Tween 60 distribution parameters were determined and the phase distribution of HCB in the presence of surfactant and biomass was described quantitatively. Both the HCB and surfactant distribution are highly dependent on the total amount of surfactant present in the system. At low initial surfactant concentrations, most of the HCB is associated with the biomass. As the surfactant concentration increases, the effect of surfactant sorption and precipitation diminishes and the higher pool of surfactant micelles shifts the distribution of HCB from the solid phase to the solution phase. The HCB phase distribution in the presence of the surfactant may have a significant effect on HCB bioavailability for reductive dechlorination. The quantitative description of the HCB phase distribution presented here was subsequently used as the basis for the development of a model that describes the bioavailability and reductive dechlorination of HCB in a surfactant/biomass system.
The Effect of Residual Chemical Oxygen Demand on Anoxic and Aerobic Phosphate Uptake and Release with Various Intracellular Polymer Levels
Authors: You S.J. , Shen Y.J. , Ouyang C.F. , Hsu C.L.
Published: September 2006

This study investigated the anoxic and aerobic phosphate uptake and release reactions and the fraction of denitrifying phosphate‐accumulating organisms (DPAOs) under various initial chemical oxygen demand (COD) and residual COD conditions. The results showed that DPAOs and non‐DPAOs could release phosphate when high soluble COD was present. Consequently, the phosphate‐uptake potential was dynamic and increased when the initial COD increased, the initial polyhydroxyalkanoates (PHA) increased, and the residual COD decreased. Furthermore, the electron acceptor (oxygen of nitrate) has more significant influence on the phosphate uptake/release characteristics, while the residual COD concentrations have little influence on that. The fraction of DPAOs to phosphate‐accumulating organisms was 42% when the initial PHA storage was enough by both DPAOs and non‐DPAOs. This was closely related to the relative phosphate uptake (47%) in the anoxic zone of the process.
Influence of Chemical Oxygen Demand/Total Kjeldahl Nitrogen Ratio and Sludge Age on Nitrification of Nitrogenous Wastewater
Authors: Sharma R. , Gupta S.K.
Published: September 2006

Four laboratory‐scale biological nitrification units (influent total Kjeldahl nitrogen [TKN] = 1002 to 1062 mg/L) were operated at chemical oxygen demand (COD)/TKN ratios of approximately 0.5, 1.0, 15, and 2.0 and at three different sludge ages of 30, 20, and 10 days to study the influence of COD/TKN, sludge age, COD loading, and TKN loading on nitrification and nitrifiers. Percent nitrification was found to increase with decreases in COD/TKN and increases in sludge age. The average nitrifier concentration increased from 460 mg/L at a COD/TKN of 2.22 and a sludge age of 10 days to 706 mg/L at a COD/TKN of 0.676 and a sludge age of 30 days. The nitrifier fraction was found to be higher at a lower COD/TKN and lower at a higher COD/TKN. The nitrifier fraction increased with the decrease in sludge age and COD loadings and the increase in TKN loadings. The effect of sludge age on the nitrifier fraction was amplified at a COD/ TKN of approximately 0.5 rather than at approximately 2.0. The nitrification rate (kilograms TKN oxidized per kilograms nitrifiers per day) was shown to be dependent on COD/TKN and sludge age. The activity performed by Nitrobacter was affected at all COD/TKN ratios studied as well as at a sludge age of 10 days. This was manifested by the accumulation of high levels of nitrite‐nitrogen in the nitrified effluent. The presence of heterotrophs did not affect nitrification rates and the growth of nitrifiers, which were found to be beneficial. High sludge age and COD loadings resulted in a higher sludge volume index of more than 200 mL/g mixed liquor suspended solids. Microscopic examination showed filamentous structure of sludge under these conditions. It is concluded from the investigations that a sludge age of 30 days and a COD/TKN of approximately 1.0 are optimal to yield maximum nitrification and nitrifier growth rates for treating high‐strength nitrogenous wastewater.
Ozone Disintegration of Excess Biomass and Application to Nitrogen Removal
Authors: Park Ki Young , Lee Jae Woo , Ahn Kyu‐Hong , Maeng Sung Kyu , Hwang Jong Hyuk , Song Kyung‐Guen
Published: September 2006

A pilot‐scale facility integrated with an ozonation unit was built to investigate the feasibility of using ozone‐disintegration byproducts of wasted biomass as a carbon source for denitrification. Ozonation of biomass resulted in mass reduction by mineralization as well as by ozone‐disintegrated biosolids recycling. Approximately 50% of wasted solids were recovered as available organic matter (ozonolysate), which included nonsettleable microparticles and soluble fractions. Microparticles were observed in abundance at relatively low levels of ozone doses, while soluble fractions became dominant at higher levels of ozone doses in ozone‐disintegrated organics. Batch denitrification experiments showed that the ozonolysate could be used as a carbon source with a maximum denitrification rate of 3.66 mg nitrogen (N)/g volatile suspended solids (VSS)·h. Ozonolysate was also proven to enhance total nitrogen removal efficiency in the pilot‐scale treatment facility. An optimal chemical oxygen demand (COD)‐to‐nitrogen ratio for complete denitrification was estimated as 5.13 g COD/g N. The nitrogen‐removal performance of the modified intermittently decanted extended aeration process dependent on an external carbon supply could be described as a function of solids retention time.
Residence Time Distribution Model for Soil Filters
Authors: Pattanaik Biplab R. , Gupta Ajay , Shankar Hariharan S.
Published: September 2006

Pulse tracer tests were carried out to determine the residence time distribution (RTD) in earthworm‐cultured and uncultured, laboratory‐scale soil filters. A two‐parallel‐cell dispersion model for the mixing behavior in soil filters is presented; the model showed excellent fit to experimental data. Results showed a fitted Peclet number of 0.83 to 0.89 for the uncultured soil filter and 0.18 to 0.29 for the cultured soil filter. Results also determined that the cultured soil filter dispersion number (1/Pe) was relatively high, showing the significant effect of earthworms on mixing. Reactor performance data and dispersion model predictions based on present RTD model parameters also reveal good agreement, indicating the usefulness of RTD parameters for describing real situations.
Determination of the Required Surface Area of a Final Clarifier for an Activated‐Sludge System
Authors: Yuen Weng Ah
Published: September 2006

A generic methodology for determining the required surface area of a final clarifier is presented. Clarification and thickening requirements are integrated to form a unified procedure for final clarifier design. The new method is based on results obtained by Yuen (2002) on the solids flux theory for a secondary clarifier; it does not require the specification of recycle rate, which is computed as an output of the method. The author shows that there is a minimum required surface area (Am) for a final clarifier under the thickening requirement when the designed recycle rate is set at the maximum allowable value (FR)m (at the critical state). The designed surface area and the return activated sludge pumping capacity can be determined by applying a safety factor to Am and (FR)m, respectively. The method is shown to conform to conventional design criteria under typical design conditions.
Comparison of Oxygen‐Transfer Measurement Methods Under Process Conditions
Authors: Capela Stéphanie , Gillot Sylvie , Héduit Alain
Published: September 2006

The objective of this paper is to compare the following four methods of measuring oxygen transfer in wastewater treatment plants under process conditions: the offgas, hydrogen peroxide (H2O2), reaeration, and in situ oxygen uptake rate (OUR) methods. Comparative tests were performed under controlled conditions in a pilot column and in six full‐scale oxidation ditches equipped with fine‐bubble diffusers and slow‐speed mixers. The offgas and H2O2 methods give similar results (differences between the oxygen‐transfer coefficients under field conditions [kLaf] from each method lower than 10%). The reaeration procedure gives more random results (differences from −5 to −43% compared with values obtained using the offgas method). The in situ OUR method, in the presence of a horizontal flow of mixed liquor, leads to an estimate of kLaf to within 15% of the offgas value.
Effects of Nitrosation on the Formation of Cyanide in Publicly Owned Treatment Works Secondary Effluent
Authors: Zheng Anping , Dzombak David A. , Zheng Richard G.
Published: September 2006

Cyanide has been detected in the effluents of some publicly owned treatment works (POTWs) at levels exceeding the influent concentration. The presence of nitrite ion (NO2− as a common constituent in domestic wastewater effluents may play an important role in the formation of cyanide through reaction with certain kinds of organic compounds, especially aromatic compounds. Laboratory studies with seven organic compounds (aniline, p‐toluidine, phenol, 1,2,4‐trihydroxybenzene, L‐serine, glycine, and benzoic acid) revealed that cyanide can be formed by reaction of nitrite with some of these compounds. The most substantial free cyanide (HCN, CN−) production observed at 25°C was 0.15 mg/L from reaction of 0.01 mM 1,2,4‐trihydroxybenze with 5 mg/L nitrite for 72 hours. Substantial free cyanide formation was also observed at pH 2‐4 in experiments with POTW effluents when reactive organics and nitrite were both added to wastewater. Formation of cyanide through nitrosation was strongly pH dependent, being most significant at low pH (2 to 4) and negligible at neutral‐to‐high pH. This result points to nitrous acid (HNO2) as being more reactive than the dissociated NO2− ion. The reaction of these nitrite species with organics also occurs in conventional analyses for total cyanide which involve distillation under strongly acidic conditions. Sufficient sample pretreatment with sulfamic acid at the time of sampling, not at the time of analysis, is highly recommended to prevent biasing analytical measurement of total cyanide in POTW effluents.
Effects of Thiocyanate on the Formation of Free Cyanide during Chlorination and Ultraviolet Disinfection of Publicly Owned Treatment Works Secondary Effluent
Authors: Zheng Anping , Dzombak David A. , Luthy Richard G.
Published: September 2006

Cyanide has been detected in effluent of some publicly owned treatment works (POTWs) at levels exceeding influent concentration. Thiocyanate (SCN−) is a cyanide‐related compoundencountered in most POTW influents and may be decomposed to free cyanide (CN−) under some circumstances. Effects of SCN− on the formation of cyanide during chlorination and UV disinfection were studied through a laboratory study with synthetic solutions and POTW secondary effluent. Results indicated that CN− was detected in SCN− solutions after chlorination in which the chlorine dose or reaction time was not sufficient to destroy SCN− completely, thus ensuring no residual chlorine to destroy any CN− produced. It was also found that SCN− can be broken down to yield cyanide by UV irradiation. In addition, SCN− was observed to cause significant positive error in the conventional total cyanide analysis technique involving acidic distillation and colorimetric measurement when nitrate was present in the sample.
Activated Sludge Deflocculation in Response to Chlorine Addition: The Potassium Connection
Authors: Wimmer Robert F. , Wimmer Nancy G.
Published: September 2006

Chlorination is often used to control filamentous bulking in activated sludge systems. Pure culture and mixed‐liquor experiments showed that soluble potassium (K+) concentrations increased by 2.4 mg/L (80%) and 1.5 to 3.6 mg/L (11 to 30%) in the bulk liquid phase of pure and activated sludge cultures that were exposed to chlorine, relative to unchlorinated controls. Effluent turbidity and total suspended solids from settled mixed liquor increased significantly in both short‐term batch and sequencing batch reactor experiments when chlorine mass load increased above 6 milligrams of chlorine per gram mixed liquor volatile suspended solids (mg Cl2/g MLVSS) in a single dose, which correlated with a localized chlorine concentration at the dose point of 10 mg/L as Cl2 or greater. The results support the hypothesis that the glutathione‐gated potassium efflux (GGKE) bacterial stress response may contribute to increased effluent turbidity associated with high doses of mixed‐liquor chlorination. It is suggested that potassium is a useful parameter to monitor at full‐scale facilities when determining chlorine mass doses that should be used to control filaments and minimize increases in effluent turbidity.
Use of Naturally Growing Aquatic Plants for Wastewater Purification
Authors: Zimmels Y. , Kirzhner F. , Roitman S.
Published: September 2006

This paper examines potential uses of n aturally growing aquatic plants for wastewater purification. These plants enhance the removal of pollutants by consuming part of them in the form of plant nutrients. This applies to urban and agricultural wastewater, in particular, where treatment units of different sizes can be applied at the pollution source. The effectiveness of wastewater purification by different plants was tested on laboratory and pilot scales. The growth rate of the plants was related to the wastewater content in the water. Batch and semicontinuous experiments verified that theplants are capable of decreasing all tested indicators for water quality to levels that permit the use of the purified water for irrigation. This applies to biochemical oxygen demand (BOD), chemical oxygen demand, total suspended solids, pH, and turbidity. In specific cases, the turbidity reached the level of drinking water. Comparison of BOD concentrations with typical levels in water treatment facilities across the country indicates the effectiveness of water purification with plants. A major effect of treatment with plants was elimination of the disturbing smell from the wastewater. It is shown that mixtures of wastewater and polluted water from the Kishon River are amenable in varying degrees to treatment by the plants. The higher the wastewater content in the mixture, the more effective the treatment by the plants. In this context, a scheme for rehabilitation and restoration of the Kishon River is presented and technical and economical aspects of the purification technology are considered.
An Experimental Study of Air Entrainment and Oxygen Transfer at a Water Jet from a Nozzle with Air Holes
Authors: Baylar Ahmet , Emiroglu M. Emin
Published: September 2006

An adequate supply of dissolved oxygen is important in natural rivers and in some water treatment processes. The dissolved oxygen concentration can be enhanced by entraining air bubbles in a receiving pool. When a water jet impinges a receiving pool at rest, air bubbles may be entrained and carried away below the pool free surface. This process is called plunging water jet entrainment and aeration. This paper describes an experimental study of the air entrainment rate and oxygen transfer efficiency of circular nozzles with and without air holes. In particular, the effect of varying the number, positions, and open/close status of the air holes is investigated. A negative pressure occurred depending on the air holes opened on the circular nozzles. This phenomenon affected the water jet expansion, water jet shape, air entrainment, and bubble penetration depth and, hence, the oxygen transfer efficiency. It was demonstrated that the air entrainment rate and the oxygen transfer efficiency of the circular nozzles with air holes were better than those of the circular nozzles without air holes. Therefore, adding air holes to a simple, circular nozzle could lead to a significantly increased air entrainment rate and oxygen transfer efficiency.
Analyzing the Uncorrected Error of Dilution Water Demand for the Dilution Biochemical Oxygen Demand Method
Authors: Chiang Chow F. , Wu Yeong S. , Young James C.
Published: September 2006

Dilution water demand (DWD) can cause a positive error when the dilution biochemical oxygen demand (BOD) method is used. Dilution water demand may be attributed to oxidation of organic impurities in the dilution water and nitrification of ammonia added as a nutrient. To minimize the error associated with these sources, the standard BOD method requires that DWD be less than 0.2 mg/L in 5 days and does not allow correction for DWD when calculating test results. This study derives a set of theoretical equations to analyze the uncorrected errors with and without seeding. The authors concluded that DWD can be completely corrected if seeded dilution water is used for the sample dilution. When seeding individual bottles, the uncorrected error approaches 8.3 to approximately 8.8% at a 5‐day depletion of 2 mg/L for a typical secondary effluent. Tests without seeding show an almost 1% higher uncorrected error than seeded tests. The analysis also suggests that these errors can be effectively reduced to less than 3% when the 5‐day depletion approaches 6 mg/L, even for 5‐day biochemical oxygen demand concentrations exceeding 1 × 104 mg/L. Further analysis indicates that, if not inhibited, the ammonium added to dilution water as a nutrient may contribute additional error due to nitrification.
Comparison of E.Coli, Enterococci, and Fecal Coliform as Indicators for Brackish Water Quality Assessment
Authors: Jin Guang , Englande A.J. , Bradford Henry , Jeng Huei‐Wang
Published: September 2006

Escherichia coli(E.coli), enterococci, and fecal coliform data were collected and comparedas potential indicators for swimmablility assessment of a brackish waterbody (Lake Pontchartrain, Louisiana). These indicators were measured during lake background conditions, in stormwater runoff (before dilution with lake water), and in the outfall plume within the lake following storm events. Microbial indicator titers associated with suspended particles and lake‐bottom sediments were also investigated. Overall reduction rate constants for fecal coliform, E.coli, and enterococci in lake water and sediment were measured and reported. Attachment of microbial indicators to suspended matter and subsequent sedimentation appeared to be a significant fate mechanism. A slower reduction rate of indicator organisms in sediment further suggested that bottom sediment may act as a reservoir for prolonging indicator organism survival and added concern of recontamination of overlaying waters due to potential solids resuspension. Results indicated that enterococci might be a more stable indicator than E.coli and fecal coliform and, consequently, a more conservative indicator under brackish water conditions.
Relative Efficacy of Intrinsic and Extant Parameters for Modeling Biodegradation of Synthetic Organic Compounds in Activated Sludge: Dynamic Systems
Authors: Magbanua Benjamin S. , Stanfill J. Chris , Fehniger Steven M. , Smets Barth F. , Farkas Ferenc , Leslie Grady C.P.
Published: September 2006

The utility of intrinsic and extant kinetic parameters for simulating the dynamic behavior of a biotreatment system coupled with a distributed, unstructured, balanced microbial growth model were evaluated against the observed response of test reactors to transient loads of synthetic organic compounds (SOCs). Biomass from a completely mixed activatedsludge (CMAS) system was tested in fed‐batch reactors, while a sequencing batch reactor (SBR) was tested by measuring SOC concentrations during the fill and react period. Both the CMAS system and the SBR were acclimated to a feed containing biogenic substrates and several SOCs, and the transient loading tests were conducted with biogenic substrates along with one or more SOCs. Extant parameters more closely reflect the steady‐state degradative capacity of activated‐sludge biomass than intrinsic parameters and, hence, were expected to be better predictors of system performance. However, neither extant nor intrinsic parameters accurately predicted system response and neither parameter set was consistently superior to the other. Factors that may have contributed to the inability of the model to predict system response were identified and discussed. These factors included the role of abiotic processes in SOC removal, disparity in the bases used to evaluate parameter estimates (substrate mineralization) and reactor performance (substrate disappearance), inhibitory substrate interactions under the severe loading conditions of the SBR, changes in the physiological state of the biomass during the transient loading tests, and the presumed correlation between the competent biomass concentration and the influent SOC concentration.
Can Chemical Oxidation Improve the Permeability of Infiltration Basins?
Authors: Amrhein Christopher , Alder Jay R. , Graham Robert C. , Housel Valerie K.
Published: September 2006

The Rapid Infiltration and Extraction (RIX) facility, a soil aquifer treatment system, began taking secondary effluent from the City of San Bernardino, California, in 1996. The gradual decreasein the hydraulic conductivity of the infiltration basins at RIX has been attributed tothe accumulation of organic matter in the surface sand. Periodic tillage of the surface sand to restore the permeability has mixed this organic matter to a depth of nearly 50 cm. We hypothesized that in situ chemical oxidation of the surface sand might improve the infiltration rate and increase the time between filling and drying cycles. The effect of organic matter oxidation on sand permeability was tested in laboratory sand columns treated with sodium hypochlorite, calcium hypochorite, and ozone gas. All oxidants significantly decreased the hydraulic conductivity of the surface sand. The loss in permeability was attributed to an increase in dispersed clay plus silt‐sized particles that were released as a result of oxidation. This study suggests that ex situ sand‐washing operations, currently being used to clean the sand, could be improved by the addition of oxidants to the wash water.
Behaviors of Intercellular Materials and Nutrients in Biological Nutrient Removal Process Supplied with Domestic Wastewater and Food Waste
Authors: Chae So‐Ryong , Jeong Hyeong‐Seok , Lim Jae‐Lim , Kang Seok‐Tae , Shin Hang‐Sik , Paik Byeong‐Cheon , Youn Jong‐Ho
Published: September 2006

A four‐stage biological nutrient removal (BNR) process was operated to investigate the effectof anaerobically fermented leachate of food waste (AFLFW) as an external carbon source on nutrient removal from domestic wastewater having a low carbon‐to‐nitrogen ratio. The BNR system that was supplemented with AFLFW showed a good performance at a sludge retention time (SRT) of 30 days, despite low temperature. With this wastewater, average removal efficiencies of soluble chemical oxygen demand (COD), total nitrogen (T‐N), and total phosphorus (T‐P) were 88 to 93%, 70 to 74%, and 63 to 68%, respectively. In this study, several kinds of poly‐hydroxyalkanoates (PHAs) were observed in cells. These included 24% poly‐3‐hydroxybutyrate (PHB), 41% poly‐3‐hydroxyvalerate (PHV), 18% poly‐3‐hydroxyhexanoate (PHH), 10% poly‐3‐hydroxyoctanoate (PHO), 5% poly‐3‐hydroxyde‐canoate (PHD), and 2% poly‐3‐hydroxydodecanoate (PHDD), indicating that microorganisms could store various PHAs through the different metabolic pathways. However, breakdown of the enhanced biological phosphorus removal (EBPR) mechanism was observed when SRT increased from 30 to 50 days for the enhancement of nitrification. To study the effect of SRT on EBPR, a sequencing batch reactor (SBR) system that was supplied with glucose was operated at various SRTs of 5, 10, and 15 days. Nitrification and denitrification efficiencies increased as SRT increased. However, the content of intracellular materials such as PHAs, glycogen, and poly‐P in cells decreased. From these results, it was concluded that SRT should be carefully controlled to increase nitrification activity and to maintain biological phosphorus removal activity in the BNR process.
Removal of Struvite to Prevent Problems Associated with its Accumulation in Wastewater Treatment Works
Authors: Stratful I. , Scrimshaw M. D. , Lester J. N.
Published: September 2006

Deposition of struvite within the infrastructure of wastewater treatment works can cause significant operating difficulties. A laboratory‐scale, two‐stage, continuously stirred tank reactor was developed to remove struvite to prevent problems associated with its deposition. Before any experimental work was conducted, the mixing regime within the system was determined using a pH‐tracer response method. Perfect mixing conditions were achieved once the stirring speed reached 500 rpm. Experiments were conducted examining the effects of various process parameters such as retention time, pH, recycling rate, and ammonium concentration. By increasing the hydraulic retention time, the residual magnesium concentration decreased, with the optimum conditions occurring at 125 minutes.
Use of Extant Kinetic Parameters to Predict Effluent Concentrations of Specific Organic Compounds at Full‐Scale Facilities
Authors: Ellis Timothy G. , Eliosov Boris
Published: September 2006

To use the results of kinetic tests to predict effluent concentrations of specific contaminants in activated sludge systems, the fraction of the biomass that has an ability to degrade the test compound (i.e., competent biomass) must be estimated. A calibration procedure was developed to assess the competent biomass concentration because the chemical oxygen demand (COD) fraction tended to underestimate the degrading fraction for three of the four test compounds. Acetone, for instance, had ameasured influent COD fraction of 0.08%, and the actual competent fraction was estimated to be 2.3%, based on the model calibration. Once the competent biomass fraction in the mixed liquor was determined, the extant kinetic parameters were subsequently used to predict activated sludge system performance. Predicted effluent concentrations were within 2, 5, and 16% of the average measured concentrations for acetone, linear alkylbenzene sulfonate, and furfural, respectively. Day‐to‐day predictions forthese compounds were less accurate, possibly because of the non‐steady‐state nature of the activated sludge systems studied. The difference between the fraction of the influent COD contributed by the target compounds and the competent biomass fraction in the mixed liquor was found to be more significant when the target compound contributed less than 1% of the influent organic matter. The chemical structure of the target compound and chemical composition of the influent likely had an effect onthe resulting competent biomass concentration. The total maximum growth rate, μX, was observed to be independent of the influent concentration of acetone and furfural, thus suggesting that the competent biomass concentration for these compounds was not affected by the changes in their influent concentrations. Consequently, a majority of competent biomass growth resulted from the degradation of other substrates, resulting in a competent biomass concentration significantly higher thanpredicted based on the influent COD fraction contributed by the test compound.
A Review of Biofouling and its Control in Membrane Separation Bioreactors
Authors: Liao B. Q. , Bagley D. M. , Kraemer H. E. , Leppard G. G. , Liss S. N.
Published: September 2006

Membrane separation technology is increasingly becoming an important innovation in biological wastewater treatment. Biofouling of the membrane is a major factor affecting the efficient and economic operation of membrane separation bioreactors (MBRs). This review summarizes the state‐of‐the‐art progress in understanding the mechanisms and factors affecting membrane biofouling and the strategies for biofouling control. Biofouling mechanisms include the adsorption of soluble and suspended extracellular polymers on membrane surfaces and in membrane pores, the clogging of membrane pore structure by fine colloidal particles and cell debris, and the adhesion and deposition of sludge cake on membrane surfaces. Design and operating conditions of membrane modules and materials, hydrodynamic conditions in MBRs, process and environmental conditions of activated sludge systems, and the physicochemical properties of the wastewater are the dominant factors determining membrane biofouling. Current strategies to control biofouling include periodic relaxation, backwashing, chemical cleaning, and possible manipulation of hydrodynamic conditions and sludge properties. Achieving full integration of MBRs in wastewater treatment technology requires further research and development. Fundamental information on the bacteria, colloid, and membrane interaction, developed through multimethod and multiscale approaches, is particularly needed.
Aerobic Sludge Digestion under Low Dissolved Oxygen Concentrations
Authors: Arunachalam Ravi Sankar , Shah Hemant K. , Ju Lu‐Kwang
Published: September 2006

Low dissolved oxygen (DO) concentrations occur commonly in aerobic digesters treating thickened sludge, with benefits of smaller digester size, much reduced aeration cost, and higher digestion temperature (especially important for plants in colder areas). The effects of low DO concentrationson digestion kinetics were studied using the sludge from municipal wastewater treatment plants in Akron, Ohio, and Los Lunas, New Mexico. The experiments were conducted in both batch digestion and amixedmode of continuous, fed‐batch, and batch operations. The low DO condition was clearlyadvantageous in eliminating the need for pH control because of the simultaneous occurrence of nitrification and denitrification. However, when compared with fully aerobic (high DO) systems under constant pH control (rare in full‐scale plants), low DO concentrations and a higher solids loadinghad a negative effect on the specific volatile solids (VS) digestion kinetics. Nonetheless, the overall(volumetric)digestion performance depends not only on the specific digestion kinetics, but also the solids concentration, pH, and digester temperature. All of the latter factors favor thelow DO digestion of thickened sludge. The significant effect of temperature on low DO digestion was confirmed in the mixed‐mode study with the Akron sludge. When compared with the well‐known empirical correlation between VS reduction and the product (temperature × solids retention time),the experimental data followed thesametrend, but were lower than the correlation predictions. The latter was attributed to the lower digestible VS in the Akron sludge, the slower digestion at low DO concentrations, or both. Through model simulation, the first‐order decay constant (kd)was estimated as 0.004 h‐1 in the mixed‐mode operations, much lower than those (0.011 to 0.029 h‐1) obtained in batch digestion. The findings suggested that the interactions among sludges with differenttreatmentages may have a substantially negative effect on digestionkinetics. The use of multistage digesters, especially with small front‐end reactors, may be advantageous in both “process” kinetics and “biological reaction” kinetics for sludge digestion.
Analysis of Microbiological Characteristics of Wastewater Along the Polishing Sequence of a Treatment Plant
Authors: Mezzanotte Valeria , Prato Nadia , Sgorbati Sergio , Citterio Sandra
Published: September 2006

Microbial populations were studied by plate counts and flow cytometry along the polishing sequence of a wastewater plant. The comparison between plate count and flow cytometry showed comparable trends, but plate counts detected less than 10% of the total intact bacteria counted by flow cytometry. Six months monitoring showed that, in spite of the high ozone doses, the disinfection effect of ozonation was insignificant. This is in agreement with the variability of ozone demand, not only related to chemical oxygen demand or total suspended solids. Membrane‐intact bacterial population decreased after ozonation, slightly regrew between ozone and biological activated carbon (BAC), and sharply increased after BAC, probably for damaged bacteria regrowth and saprophytes release; BAC effluent had the highest bacterial counts. Preliminary investigations on the effluent microbial composition showed that the beta Proteobacteria subclass is the most represented in the BAC effluent, whereas the alpha subclass is the most sensitive to ozone effect.
Heterotrophic Community‐Level Physiological Profiles of Domestic Wastewater Following Treatment by Small Constructed Subsurface Flow Wetlands
Authors: Hench Keith R. , Sexstone Alan J. , Bissonnette Gary K.
Published: September 2006

Seasonal treatment performance of small‐surface flow wetlands was evaluated during their second operational year and compared with community‐level physiological profiles (CLPP) of the heterotrophic bacterial community obtained from sole‐carbon source utilization patterns in BIOLOG GN (Haywood, California) microplates. The CLPP patterns varied significantly by season, indicating reduced functional diversity in the heterotrophic community during warmer months of active plant growth (April through October). Principal component analysis (PCA) suggested that the functional community differed in planted versus unplanted wetlands during the growing season. Wetlands generally improved wastewater quality; however, treatment performance was reduced in the second year. Despite differences in the heterotrophic community suggested by CLPP, treatment efficiency with respect to removal of five‐day biochemical oxygen demand or reduction in fecal indicator organisms generally was not significantly changed as a function of growing season or plant treatment.