Bluffer’s Park Beach in the Toronto and Region Area of Concern had a history of beach postings often exceeding 80% of the beach season since the 1980s. A study applied expanded E. coli surveillance and microbial source tracking techniques in 2005–2007 to identify fecal pollution sources contributing to beach postings. Expanded surveillance in the beach vicinity identified significant E. coli hotspots in the foreshore beach sand (pore water max E. coli = 255,000 CFU 100 ml−1) and associated with a marsh inland of the beach. During rain events, streams from the marsh (max E. coli = 173,000 CFU 100 ml−1) and runoff from the parking lot (max E. coli = 4100 CFU 100 ml−1) were observed to overflow across the beach to contaminate beach waters. Microbial source tracking using library-dependent (antibiotic resistance and rep-PCR DNA fingerprinting of E. coli isolates) and library-independent (human HF183 bacterial DNA marker) methods indicated the prevalence of animal fecal pollution sources at the beach rather than human sewage. These results were consistent with sanitary survey information, observations of wildlife in the marsh area, and Gulls and Canada Geese on the beach. In 2006, a bird management program was initiated, and remedial actions continued in advance of the 2008 bathing season to engineer a berm to prevent marsh runoff into beach water and re-direct parking lot drainage into the marsh. Since these remediation actions, Bluffer’s Park Beach has been posted less than 20% of each beach season, and it was awarded a Blue Flag accreditation in 2011.

Ultraviolet (UV) disinfection of wastewater is adversely affected by the presence of particle-associated bacteria. Earlier studies have shown that disrupting these particles by ultrasonic cavitation can enhance the UV disinfection of wastewater. However, the use of ultrasound as a pretreatment technology for UV disinfection is hindered by its high energy demand. In this work, the addition of several organic solutes, including 1-propanol, 1-hexanol, and pentyl acetate, to promote the cavitation process and to improve the breakage of wastewater particles was examined. It was found that the enhancement in the cavitation and the breakage efficiency of particles was positively related to the hydrophobicity of surfactant. In addition, particle breakage was a function of the concentration of surfactant as well as the delivered ultrasound energy density. Sonication of wastewater samples containing small amounts of 1-hexanol (16 mM) or pentyl acetate (12 mM) increased the UV disinfection efficiency and decreased the required UV dose to achieve the disinfection target by a factor of more than 2.5.

The aim of this research was to better understand chemical pre-treatment of combined sewer overflows (CSOs) for subsequent ultraviolet (UV) disinfection. Approximately 200 jar tests were completed. Alum (Al2(S04)3·12H2O) resulted in a higher UV light transmission (UVT), and equivalent total suspended solids (TSS) removal, than ferric chloride (FeCl3). An alum dose of 20 mg/L increased the UVT of the raw CSO from 30 to 60% after settling. The addition of 100 mg/L of alum maximized UVT reaching approximately 85%. Flocculation did not increase UVT. However, it did improve the removal of TSS. Cationic polymers worked quickly compared with metal coagulants, but only reached a UVT of 60%. A high positive charge density on the polymer improved the removal of turbidity when compared with low charge, but did not affect UVT. If the goal is to maximise UVT, a very high alum dose may be preferred. If the goal is to minimize coagulant dose with moderate UV performance, cationic polymer at approximately 3 mg/L is recommended.

Bench scale experimentation was completed to assess the potential of using a short residence time pretreatment reactor upstream of aerobic digestion to enhance the destruction of pathogens. The impact of aeration, temperature, hydraulic residence time (HRT), solids concentration, and feeding frequency on the pretreatment process was investigated. Subsequent testing evaluated pathogen destruction resulting from the operation of selected pretreatment conditions in a staged configuration with conventional aerobic digesters. Either highly oxidative or highly reductive conditions were observed to be most effective in reducing the concentrations of E. coli. and Salmonella spp. in the pretreatment reactor. When operated in series with the aerobic digesters, the more highly reducing conditions in pretreatment were found to enhance die-off of the microorganisms in subsequent aerobic digestion compared to the control.

Dark fermentative hydrogen production under the effect of zero-valent metal shavings (iron, aluminum and copper) was studied by using a sucrose medium and a mixed bacterial consortium. The iron shavings were found to be unique to promote the hydrogen production, the hydrogen yield obtained from an optimal dose of 8-16 g/L reached 4.2 mol/mol hexose, doubled compared with that obtained from the control without addition of the iron shavings. The effect was more obvious in low pH buffered medium than in higher buffered medium. The aluminum and copper shavings were either inert or toxic to the cultivation. It is evident that the addition of the zero-valent iron helped maintaining the pH to an optimal range for hydrogen production and drove more reducing equivalents to the production of hydrogen. A microbial corrosion system mediated by the hydrogen producing bacteria was proposed to be responsible for the improvement of hydrogen production. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

This study tested municipal sewage effluents generated at the pilot scale using conventional activated sludge (CAS), nitrifying activated sludge (CAS-N) and biological nutrient removal (BNR) in terms of the removal of trace organic compounds (TrOCs) and final effluent quality as indicated by yeast estrogenicity screening (YES), short term zebrafish reproduction and fathead minnow life-cycle tests. Under cold weather conditions (extended SRTs), the BNR configuration reduced the concentrations of the largest number of TrOCs while under warm weather conditions (reduced SRTs) the CAS-N was most effective. By comparison, YES test results indicated statistically lower responses in the BNR effluent in the warm weather tests and no difference between the effluents of CAS-N and BNR in the cold weather tests. Short term tests with adult zebrafish revealed no impact of the BNR and CAS-N effluents on egg production. By contrast egg production and gene expression in the CAS-exposed zebrafish were substantially less than that of control exposures and were similar to that of exposures to ammonia at similar concentrations as the CAS exposures. In fathead minnow life-cycle tests, exposures to CAS effluent (70-50% v/v) resulted in considerable mortality, reduced growth and reduced egg production that was likely due to the elevated ammonia concentrations. The CAS-N effluent (100% v/v) also resulted in some mortality and reduced growth and egg production in the fathead minnows. By contrast, the BNR effluent (100% v/v) had no effect on mortality, growth or egg production. The results suggest that enhancements to wastewater treatment plants that are associated with improved nitrogen removal can result in enhanced removal of TrOCs and can reduce the harmful effects of the effluents on aquatic biota.

Pilot-scale sequencing batch reactors (SBRs) were used to assess the effects of sludge retention time, temperature, and influent phosphorus level on floc physicochemical characteristics, effluent quality, and UV disinfection kinetics. Increasing the operating temperature from 12 to 22 °C caused an increase in the activated sludge flocs fractal dimension from 0.1 to 0.2, and improved the UV disinfection of final effluent. Influent phosphorus limitation, i.e., COD:N:P of 100:10:0.3, caused the formation of more spherical flocs with higher resistance to UV disinfection (by 1 log). However, influent phosphorus starvation, i.e., COD:N:P of 100:10:0.03, decreased the average floc size and sphericity, increased the final effluent turbidity, and lowered effluent UV dose demand. The findings provide useful information in terms of modifying wastewater treatment processes in the context of water reuse and improving UV disinfection efficiency.

Activated sludge flocs that are carried to the final effluent can significantly decrease the effectiveness of ultraviolet (UV) disinfection of wastewater. This effect is detected in a typical UV dose-response curve, where at higher UV doses there is a decrease in the inactivation rate (tailing). In this study, the effect of activated sludge process conditions on the UV inactivation kinetics of flocs was investigated. The conditions compared were nitrifying vs. non-nitrifying vs. an enhanced biological nutrient removal-University of Cape Town (BNR-UCT) system. The results showed that the flocs generated in the BNR-UCT process were easier to disinfect. The final effluent from the BNR-UCT process also showed improved kinetics of inactivation and reached higher levels of disinfection. The nitrifying system's final effluent had a lower number of initial fecal coliforms, which contributed to reaching higher disinfection levels compared to the non-nitrifying system.

The Effect of Secondary Treatment Operating Temperature and Sludge Retention Time on UV Disinfectability of Final Effluents and Sludge FilterabilityThis work investigates the effect of operating temperature and sludge retention time (SRT) on the final effluent quality, UV disinfectability, and sludge filterability in treating municipal wastewater. The temperatures and sludge retention times studied were 12 °C & 22 °C, and 7 & 20 days, respectively. Four sequencing batch reactors, treating real municipal wastewater, were setup...Author(s)Y. AzimiP. AminD. G. AllenP. SetoR. R. FarnoodSourceProceedings of the Water Environment FederationDocument typeConference PaperPublisherWater Environment FederationPrint publication date Oct, 2013ISSN1938-6478DOI10.2175/193864713813715931Volume / Issue2013 / 9Content sourceWEFTECCopyright2013Word count179

This article presents the results of pilot scale studies that examined the use of negative and neutral charged tubular and hollow fiber (HF) anaerobic membrane bio‐reactors (AnMBR) for anaerobic digestion of waste activated sludge. Both AnMBR configurations were operated at a hydraulic retention time of 15 days, a sludge retention time (SRT) of 30 days, and a total solids loading of 1.2–1.3 kg m−3 day−1. The results indicate that both membrane digesters showed comparable total chemical oxygen demand and volatile solids removals of 47.6 and 49.1% respectively while maintaining a throughput that was two times that of the completely stirred tank reactor (CSTR) type digesters. The performance of the AnMBRs was similar to that of CSTRs operating at 30 days SRT. The AnMBRs were operated for 160 days. During this period no significant fouling was observed and membrane cleaning was not required. The average fluxes for the neutral and negative tubular membranes were 32 and 39 LMH when operated at a trans‐membrane pressure TMP of 30 kPa. The HF membranes were operated at a constant flux of 11 LMH and the average TMP was less than 10 kPa. The critical flux measured for the tubular and HF membranes were near to 30 and 18 LMH mark respectively indicating a better performance by the former. However both AnMBR configurations generated comparable net energy. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 598–604, 2013

Waste-activated sludge (WAS) samples that were generated over a range of solids residence times (SRTs) under controlled operating conditions were employed in bench-scale sonication tests to characterize the impact of physical pretreatment processes on WAS anaerobic digestion and to assess the applicability of indicators for characterizing WAS digestibility. Physical, chemical, and biochemical analyses were conducted on raw and pretreated WAS samples and the results were compared to those obtained in biochemical methane potential (BMP) and biochemical acid potential (BAP) tests. The solublization responses indicated that the materials that were solublized were affected by the WAS SRT and sonication level. Despite differences in solublization responses, BMP tests revealed that sonication only marginally increased the ultimate biodegradability of the sludges. NH4 responses from the BMP tests and volatile fatty acids (VFAs) responses from the BAP tests were found to be indicative of the impact of sonication on the rate of hydrolysis and acidification/ammonification. Both responses suggested an increase in the rate of hydrolysis, which is typically the rate-limiting process in WAS digestion. DOI: 10.1061/(ASCE)EE.1943-7870.0000657. (C) 2013 American Society of Civil Engineers.

The potential to use the results of biochemical acid potential (BAP) tests to predict the ultimate digestibility of raw and pretreated waste activated sludge (WAS) was investigated. The ultimate methane production from biochemical methane potential (BMP) tests on raw and pretreated samples which spanned a range of biodegradability proved linearly related to the volatile fatty acid (VFA) and soluble chemical oxygen demand (COD) production in corresponding BAP tests. In addition, a linear relationship between NH 4 ‐N production in the BMP and BAP tests was observed. Despite the linear nature of the relationships, the ratio of the production of methane in the BMP tests to the production of VFAs in the BAP tests varied with the biodegradability of the sludge samples. Waste Activated Sludge samples with low digestibility had ultimate yields of CH 4 that were greater than the VFA yields in BAP tests, whereas sludge samples with high digestibility had lower yields of CH 4 than the corresponding VFA yields. This trend contrasted with the NH 4 results, in which the yields in the BAP tests were consistently less than those observed in the BMP tests. It was hypothesized that the varying relationship between CH 4 and VFA yields was because of the inhibition of anaerobic oxidation of long‐chain fatty acids (LCFAs) in the BAP tests. Long‐chain fatty acids would be converted to CH 4 in BMP tests but produced as digestion intermediates in the BAP tests and were not measured as part of the VFA yield. Hydrogen and acetate were identified as the two most likely intermediates that would accumulate in the BAP tests (which would cause inhibition). A stoichiometric model to facilitate the development of an improved understanding of the biodegradation processes in the BAP and BMP tests was assembled. When the model was applied to the BAP tests the anaerobic oxidation of LCFAs and propionate and methanogenesis were excluded from the model. The model was employed to estimate the extent of degradation of lipids, carbohydrates, and proteins in the batch tests as a function of the ultimate biodegradability of the sludge samples. On the basis of model fitting, it was determined that the degradation of lipids in BMP tests decreased, whereas the degradation of carbohydrates and proteins increased as the digestibility of the sludge samples increased. The varying ratio of lipid to protein and carbohydrate degradability with increasing digestibility of the sludge samples describes the relationship between VFA production and CH 4 production in the BAP, and BMP tests, respectively.

There is limited information on the impact of sludge characteristics, membrane type and operation parameters on membrane fouling under anaerobic conditions. This paper examined filtration characteristics of anaerobic sludges with solids concentration between 6 and 33g/L and the interaction with negatively and neutral charged membranes at various fluxes within the subcritical region. The study employed a short term filtration protocol using a bench-scale tubular ultra-filtration membrane operated at a cross-flow velocity of 1m/s and under constant pressure. The results showed that the effects of anaerobic sludge concentration and membrane surface charge on membrane fouling were a function of the operating flux. Their impact on fouling was found to be minimal at the lower fluxes (8LMH) however detrimental at higher fluxes (30LMH). Further study on impact of anaerobic sludge composition on membrane fouling indicated that the decline in membrane performance at the higher subcritical fluxes was associated mainly with the colloidal fraction when the suspended solids concentrations were less than 20g/L whereas at higher concentrations both the solids and colloidal fractions contributed to development of the fouling layer. Integration of a relaxation cycle and addition of cationic polymer were found to be effective in controlling anaerobic membrane fouling.

Hydrodynamic forces generated by an orifice plate under low pressure were examined as a means of disrupting flocs, in order to improve disinfection of treated wastewater effluents. Changes in cavitation conditions were found to have little impact on the extent of particle breakage in this experimental setup. The rate of strain (flow rate divided by the hole radius cubed), however, was found to be the best predictor of floc breakage. Floc breakage was not affected by changes in floc concentration, but was very sensitive to differences between flocs collected from different sources. Larger flocs (90 to 106 µm) were broken apart to a greater extent than smaller ones (53 to 63 µm). Hydrodynamic treatment decreased the viability of bacteria associated with large flocs, and also increased the ultraviolet dose response by up to one log unit (i.e., a factor of ten). Subjecting final effluent wastewaters to hydrodynamic treatment, therefore, provides a treatment strategy for conditions in which the presence of flocs limits the level of disinfection that can be achieved.

Soreanu, G., M. Béland, P. Falletta, K. Edmonson, L. Svoboda, M. Al-Jamal and P. Seto. 2011. Approaches concerning siloxane removal from biogas* A review. Canadian Biosystems Engineering/Le génie des biosystèmes au Canada. 53: 8.1 8.18. One of the major barriers to the use of biogas as an alternative renewable energy source is the presence of siloxanes. At combustion temperatures, siloxanes are converted to silicon dioxide (SiO2), which forms deposits on the combustion surfaces (pistons and cylinders) of gas processing equipment, thus reducing engine life and increasing overall operational and maintenance costs. This paper presents key multidisciplinary information with respect to siloxane removal, aimed at evaluating various treatment options and identifying future research needs. Current removal methods are typically based on the adsorption process, while others employ gas liquid absorption and refrigeration/ condensation. Otherwise these methods are appropriate for siloxane removal with regard to siloxane physical chemical characteristics (for example, low solubility in water, high solubility in organic solvents, volatility, chemical resistance) their application in practice is cost-limited. Adsorption and absorption methods become inappropriate when applied to moisture-rich biogas, and are often used in combination with a pre-treatment stage. Development of more cost-effective technologies, such as membrane separation and biofiltration is in progress, and initial findings suggest that these methods could represent an attractive alternative.