Municipal Wastewater Plant Research Articles

Environmental assessment of different dewatering and drying methods on the basis of life cycle assessment

Sewage sludge is an inevitable product of wastewater treatment in municipal wastewater plants and its amount has increased dramatically due to the growing number of sewage systems users. This sludge needs to be adequately treated in order to decrease its hazardous properties and any negative influence on the environment. In this paper, gate to gate analysis, on the basis of life cycle assessment (LCA), was carried out in order to compare the environmental impact of alternative ways of sludge processing employing a dewatering press and three different kinds of dryers - belt dryer, container dryer and batch dryer. SimaPro 7.2 software and Ecoinvent 2.2 database were used to estimate the carbon footprint and energy balance of these processes. The main energy consumption in the scenarios analyzed is caused by the drying process. The solution based on application of the batch dryer allows a saving of 39.6% of energy compared with the most energy-consuming solution using a belt dryer. Sludge processing using belt and container dryers cause greater environmental burdens.

Identifying the microbial communities and operational conditions for optimized wastewater treatment in microbial fuel cells

Microbial fuel cells (MFCs) are devices that exploit microorganisms as “biocatalysts” to recover energy from organic matter in the form of electricity. MFCs have been explored as possible energy neutral wastewater treatment systems; however, fundamental knowledge is still required about how MFC-associated microbial communities are affected by different operational conditions and can be optimized for accelerated wastewater treatment rates. In this study, we explored how electricity-generating microbial biofilms were established at MFC anodes and responded to three different operational conditions during wastewater treatment: 1) MFC operation using a 750 Ω external resistor (0.3 mA current production); 2) set-potential (SP) operation with the anode electrode potentiostatically controlled to +100 mV vs SHE (4.0 mA current production); and 3) open circuit (OC) operation (zero current generation). For all reactors, primary clarifier effluent collected from a municipal wastewater plant was used as the sole carbon and microbial source. Batch operation demonstrated nearly complete organic matter consumption after a residence time of 8–12 days for the MFC condition, 4–6 days for the SP condition, and 15–20 days for the OC condition. These results indicate that higher current generation accelerates organic matter degradation during MFC wastewater treatment. The microbial community analysis was conducted for the three reactors using 16S rRNA gene sequencing. Although the inoculated wastewater was dominated by members of Epsilonproteobacteria, Gammaproteobacteria, and Bacteroidetes species, the electricity-generating biofilms in MFC and SP reactors were dominated by Deltaproteobacteria and Bacteroidetes. Within Deltaproteobacteria, phylotypes classified to family Desulfobulbaceae and Geobacteraceae increased significantly under the SP condition with higher current generation; however those phylotypes were not found in the OC reactor. These analyses suggest that species related to family Desulfobulbaceae and Geobacteraceae are correlated with the electricity generation in the biofilm and may be key players for optimizing wastewater treatment rates and energy recovery in applied MFC systems.

The Effectiveness of Single Oxidants and AOPs in the Degradation of Emerging Contaminants in Waters: A Comparison Study

The effectiveness of single oxidants and several AOPs was studied for the degradation of five selected emerging contaminants: Benzotriazole, N,N-diethyl-m-toluamide or DEET, Chlorophene, 3-Methylindole and Nortriptyline HCl. First-order rate constants and half-life times for the degradation of each compound in ultra-pure water were deduced and compared. The AOPs were later applied to the degradation of these ECs present in three real waters: public reservoir water, and two secondary effluents from municipal wastewater plants. The effect of the variables on the ECs elimination was established. Finally, a cost estimation based on the operating costs was established for the degradation of 3-Methylindole by the single oxidants and AOPs tested.

Optimization of solid phase microextraction for non-lethal in vivo determination of selected pharmaceuticals in fish muscle using liquid chromatography–mass spectrometry

A new thin film microextraction (TFME) configuration based on C18 thin film was optimized to improve solid phase microextraction (SPME) sensitivity and extraction kinetics for in vivo determinations of trace pharmaceuticals in fish tissue. Optimization of SPME involved increasing sampler surface area and volume of extraction phase to improve performance within in vitro applications such as agarose gel matrix and spiked fish tissue, as well as in vivo determinations of pharmaceuticals in fish exposed to municipal wastewater. Rainbow trout (Oncorhynchus mykiss) were exposed for 4d to effluents from a municipal wastewater plant that was treated under three different configurations of a pilot plant. Fathead minnow (Pimephales promelas) were caged for 14d upstream and downstream of municipal wastewater effluent discharges along Grand River at near Kitchener, ON. TFME and regular C18 fibers were inserted into the dorsal-epaxial muscle of rainbow trout and fathead minnow, respectively, for 30min sampling intervals. Sample extracts obtained from fibers were desorbed in methanol:water (3:2) for 90min under 1500rpm agitation and analyzed using liquid chromatography coupled with tandem mass spectrometry (LC/MS–MS) to determine pharmaceutical bioconcentration. Most target pharmaceuticals were detected in the wastewater with the exception of norfluoxetine and paroxetine. C18 TFME phase successfully quantified fluoxetine, venlafaxine, sertraline, paroxetine, and carbamazapine in muscle of living fish at concentrations ranging from 1.7 to 259ng/g. Reproducibility of the method in spiked fish muscle was 9–18% RSD with limits of detection and quantification ranging from 0.08 to 0.21ng/g and 0.09 to 0.64ng/g (respectively) for the analytes examined. Ibuprofen and gemfibrozil were not detected in fish tissues, likely due to rapid excretion leading to low rates of bioconcentration. This study demonstrates improved in vivo SPME sensitivity (recovery) and extraction rates during pre-equilibrium sampling of target pharmaceuticals in fish tissue due to the improved C18 extraction phase geometry.

Overcoming the toxicity effects of municipal wastewater sludge and biosolid extracts in the Yeast Estrogen Screen (YES) assay

For nearly two decades, the Yeast Estrogen Screen (YES) has been used as a valuable tool for determining the total estrogenic potency of various environmental samples, including influent and effluent streams at municipal wastewater plants. However, applying the YES assay to wastewater sludges and stabilized biosolids has been problematic. This is due to co-extracted compounds from the solids either proving toxic to the yeast or masking the presence of estrogenic substances. The present research describes the development and validation of sample preparation steps that mitigate the toxicity effects of municipal wastewater sludge and biosolid samples in the YES assay, while allowing for reliable dose-dependent expression of estrogenic activity. A copper work-up for sulfur removal and chromatographic cleanup with silica and alumina were required in addition to solid-phase extraction to adequately remove interfering compounds. Sample stabilization methods such as autoclaving, lyophilization and formaldehyde treatment were found to be detrimental to the assay. Hence, heat-drying is recommended to prevent cytotoxicity and the degradation of estrogenic substances.

Water reuse: >90% water yield in MBR/RO through concentrate recycling and CO 2 addition as scaling control

Over 1.5 years continuous piloting of a municipal wastewater plant upgraded with a double membrane system (ca. 0.6 m 3 d −1 of product water produced) have demonstrated the feasibility of achieving high water quality with a water yield of 90% by combining a membrane bioreactor (MBR) with a submerged ultrafiltration membrane followed by a reverse osmosis membrane (RO). The novelty of the proposed treatment scheme consists of the appropriate conditioning of MBR effluent prior to the RO and in recycling the RO concentrates back to the biological unit. All the 15 pharmaceuticals measured in the influent municipal sewage were retained below 100 ng L −1, a proposed quality parameter, and mostly below detection limits of 10 ng L −1. The mass balance of the micropollutants shows that these are either degraded or discharged with the excess concentrate, while only minor quantities were found in the excess sludge. The micropollutant load in the concentrate can be significantly reduced by ozonation. A low treated water salinity (<10 mM inorganic salts; 280 ± 70 μS cm −1) also confirms that the resulting product has a high water quality. Solids precipitation and inorganic scaling are effectively mitigated by lowering the pH in the RO feed water with CO 2 conditioning, while the concentrate from the RO is recycled to the biological unit where CO 2 is stripped by aeration. This causes precipitation to occur in the bioreactor bulk, where it is much less of a process issue. SiO 2 is the sole exception. Equilibrium modeling of precipitation reactions confirms the effectiveness of this scaling-mitigation approach for CaCO 3 precipitation, calcium phosphate and sulfate minerals.

The azo dye Disperse Orange 1 induces DNA damage and cytotoxic effects but does not cause ecotoxic effects in Daphnia similis and Vibrio fischeri

Azo dyes constitute the largest group of colorants used in industry and can pass through municipal waste water plants nearly unchanged due to their resistance to aerobic treatment, which potentially exposes humans and local biota to adverse effects. Unfortunately, little is known about their environmental fate. Under anaerobic conditions, some azo dyes are cleaved by microorganisms forming potentially carcinogenic aromatic amines. In the present study, the azo dye Disperse Orange 1, widely used in textile dyeing, was tested using the comet, Salmonella/microsome mutagenicity, cell viability, Daphnia similis and Microtox ® assays. The human hepatoma cell line (HepG2) was used in the comet assay and for cell viability. In the mutagenicity assay, Salmonella typhimurium strains with different levels of nitroreductase and o-acetyltransferase were used. The dye showed genotoxic effects with respect to HepG2 cells at concentrations of 0.2, 0.4, 1.0, 2.0 and 4.0 μg/mL. In the mutagenicity assay, greater responses were obtained with the strains TA98 and YG1041, suggesting that this compound mainly induces frameshift mutations. Moreover, the mutagenicity was greatly enhanced with the strains overproducing nitroreductase and o-acetyltransferase, showing the importance of these enzymes in the mutagenicity of this dye. In addition, the compound induced apoptosis after 72 h in contact with the HepG2 cells. No toxic effects were observed for either D. similis or Vibrio fischeri.

Intersex and reproductive impairment of wild fish exposed to multiple municipal wastewater discharges

The Grand River watershed in Ontario, Canada, receives and assimilates the outflow of 29 Municipal Wastewater Effluent (MWWE) discharges which is a mixture of domestic and industrial wastes. The purpose of this study was to investigate the cumulative impact of multiple sewage discharges on populations of wild fish. In field studies, responses of fish populations and individual fish responses in terms of growth (condition factor), reproduction (in vitro sex steroid production, gonadosomatic indices, histology [cellular development and intersex]) were assessed upstream and downstream of two municipal discharges. Fish [Greenside Darters Etheostoma blennioides and Rainbow Darters E. caeruleum] collected downstream of two municipal wastewater plants had the potential to have greater growth (longer and heavier) when compared to reference fish collections regardless of sex. Fish were not assimilating additional anthropogenic resources into energy storage (increased condition, liver somatic index). Impacts on ovarian development appeared to be minor with no differences in growth, steroid production or cellular development. Sewage exposed male fish were experiencing impairment in the capacity to produce testosterone and 11-ketotestosterone in vitro, and in cellular development (GSI, intersex). Male darters of both species collected in the upstream agricultural region demonstrated no evidence of intersex whereas our urban reference sites had incidence of intersex of up to 20%. Rates of intersex were elevated downstream of both sewage discharges studied (33% and>60%, respectively). Lower rates of intersex at the intermediate sites, and then increases downstream of second sewage discharge suggests that fish populations have to potential to recover prior to exposure to the second sewage effluent. Pre-spawning darters demonstrated dramatically higher incidence of intersex in the spring at both urban reference sites (33% and 50%, respectively), and increased more so downstream of the near-field and far-field exposure sites (60% and 100%, respectively). These findings suggest that the compounds released in STP effluents have a tendency to act on the male reproductive system. These effects may become more pronounced as projected human population growth will require the aquatic environment to assimilate an increasing amount of sewage waste.

Two New Designs for Manure Solids and Liquids Sampling from Tank, Pit, and Lagoons at Various Depths

The wide variety of animal manure slurry storage structures and the spatially heterogeneous nature of manure within the storage structure present a difficult challenge to researchers studying the composition and activities within manure storage systems. The objective of this study was to design and construct a manure sampling system that could be used to sample manure at various depths greater than 7.6 m (25 ft) from a variety of swine manure storage systems, including deep pit, lagoon systems, and above ground manure slurry storage tanks. Two slurry sampler systems were devised that could be lowered to a variety of depths within the manure slurry and then opened and closed remotely in order to collect a sample from a specific depth with minimal contamination from manure slurry from shallower or deeper depths. Over more than a year, these two samplers were repeatedly field tested at four animal production sites. These two designs proved to be low cost, robust, and possessed a combination of several features (easily transportable, large sample orifice, minimal sample contamination, ample volume collection, and variable depth collection) that were not available in commercially-available wastewater collection systems designed for sample collection at municipal wastewater plants.

Pilot Studies on Cloth Media Filter Applied in WWTP for the Treatment of Secondary Effluent

Cloth media filter was applied in the treatment of the effluent of a municipal wastewater plant through pilot scale test for water reuse. Ferric chloride (FeCl3), PAFC and polyaluminum chloride (PAC) were employed as coagulants respectively to carry out the test. The average removal efficiency of TP and CODCr was 28.76% and 8% after cloth media filter without coagulation, and TP removal was influenced by the influent water quality. However, precoagulation with coagulants of ferric chloride, PAFC, PAC, the average removal efficiency of TP was 63.58%, 60.13%, 66.94% respectively, and no influence of TP removal can be found by the influent water quality. The average removal efficiency of CODCr was increased to 17.7%、26.3% and 27.7%，SS was 70.7%、64.3% and 49.1%. TN and NH3-N were removed unstably after cloth media filter.

Biological reduction of nitrate and perchlorate in brine water using up-flow packed bed reactors

Denitrifying up-flow packed bed bioreactors (UPBRs) were evaluated for their capacity to simultaneously remove nitrate and perchlorate from ion exchange regenerant brines. A continuous-flow UPBR, which was inoculated with denitrifying bacteria obtained from a municipal wastewater plant, completely removed perchlorate as well as nitrate in conditions of up to 10% salinity. When nitrate and perchlorate were added to the UPBR, they were removed immediately. To investigate factors that affected the contaminant removal, acetate (as an electron donor) and sulfate (as a competing electron acceptor) were added at different salinities. Lower carbon loading decreased the nitrate and perchlorate reductions, but increased sulfate loading did not decrease the reductions of nitrate and perchlorate. In conclusion, the UPBR is a useful and powerful technology that simultaneously removes nitrate and perchlorate in brine.

Molecular Typing of Enteroviruses, Adenoviruses, and Hepatitis A Viruses in Untreated and Treated Sewage of a Biological Treatment Plant in Greece

The effluents of a sewage treatment plant may contain infectious human viruses representing a major public health issue. In the present study, an 8 months survey was conducted in order to evaluate the presence of enteroviruses (EV), adenoviruses (AdV), and hepatitis A viruses (HAV) in untreated and treated sewage samples collected from a primary treatment municipal wastewater plant, located in the northeastern Greece. Reverse transcriptase-polymerase chain reaction (RT-PCR) and nested polymerase chain reaction techniques have been applied for viral nucleic acid detection. Positive samples were confirmed by sequencing, and comparative phylogenetic analysis was performed on the isolated viral strains. EVs, AdVs, and HAV have been detected in 40% (10/25), 40% (10/25), 4% (1/25) of the samples collected from the plant’s inlet, and in 12% (3/25), 44% (11/25), 0% (0/25) of the samples collected from the plant’s outlet. Adenovirus types 3 (Ad3), 10 (Ad10) and 41 (Ad41), and hepatitis A virus type H2 have been recognized, while for enteroviruses Coxsackie type A2 and Echovirus types 27 and 30 have been recorded. The results suggest that treated sewage may still contain human viruses and thereby represent a potential health hazard. Moreover, their possible reuse in agriculture or elsewhere must be considered with concern. Furthermore, this study shows the usefulness of molecular methods for virus detection, typing and virological quality analysis of sewage treatment plants.

Investigating the link between pulp mill effluent and endocrine disruption: Attempts to explain the presence of intersex fish in the Wabigoon River, Ontario, Canada

The ability of some pulp mill effluents (PME) to act as reproductive and endocrine disrupters in fish is well documented in the literature. However, changes are not always consistent with regard to species, gender, hormones, or reproductive effects. In the present study, the presence of the first intersexed fish that, to our knowledge, has been found in a Canadian river exposed to PME, is reported. A field survey of the Wabigoon River near Dryden, Ontario, in the fall of 2000 found intersexed walleye (Sander vitreus vitreus) with significantly altered hormone levels and reduced gonad size. The Wabigoon River receives discharge from a bleached kraft pulp and paper mill and a municipal wastewater (MWW) plant. It also has historical sediment contamination (wood fiber mats) contributing to extended periods of low dissolved oxygen under low flow, drought conditions. A mesocosm-based partial life cycle test exposing fathead minnows (Pimephales promelas) to reference water, 20% effluent volume to river volume (v/v), 40% (v/v), or 60% (v/v) PME as well as a field survey of the walleye in the Wabigoon River were conducted. The only change in our mesocosm exposure was a decrease in testosterone in males with increasing effluent concentration and vitellogenin induction in males exposed to 60% (v/v) effluent. These results did not reflect the magnitude of endocrine disruption seen in the wild fish survey. Several hypotheses that may explain these discrepancies are proposed. Specifically, evidence is offered from published studies indicating that either hypoxia or MWW, alone or in combination with PME, may explain the discrepancy between our field experiment and the wild fish survey. The present study illustrates the complexities of multistressor receiving environments and the need for the development of cumulative effects assessment approaches.

Effective Biological Nitrogen Removal Treatment Processes for Domestic Wastewaters with Low C/N Ratios: A Review

Abstract Discharge of nitrogenous components to water bodies can cause eutrophication, deterioration of water quality, toxicity to aquatic life, and pose a potential hazard to human and animal health. Biological nitrogen removal can remove nitrogenous components via conversion to harmless nitrogen gas with high efficiency and relative low costs. However, the removal of nitrogen from domestic wastewater with a low carbon/nitrogen (C/N) ratio can often be limited in municipal wastewater plants (WWTPs) because organic carbon is a limiting factor for denitrification. The present work reviews innovative bacterial nitrogen removal pathways such as shortcut nitrification/denitrification, simultaneous nitrification/denitrification, and the nitritation Anammox process, which can remove nitrogen with low or zero dosage of organic carbon sources. We conclude that advanced process control and some new biological treatment processes including the modified anaerobic/anoxic/oxic (A2/O) process, the step-feed multistage ...

Membrane filtration technologies applied to municipal secondary effluents for potential reuse

Four UF membranes (denoted GH, GK, PT and PW with MWCO of 1000, 2000, 5000 and 20,000 Da, respectively) and four NF membranes (denoted DL, CK, DK and HL, with an approximate MWCO of 150–300 Da in all cases) were used for the filtration of an effluent generated in a municipal wastewater plant after a secondary treatment. The influence of the most important operating variables (nature and MWCO of the membranes, transmembrane pressure, tangential velocity, and temperature) on the permeate flux was widely discussed, and the resistances to the permeate flux were determined following the resistances in series model. Rejection coefficients for parameters that measure the global pollutant content of the effluent (chemical oxygen demand, total organic carbon, absorbance at 254 nm, turbidity, total nitrogen and total phosphorus) were also evaluated, and the results revealed that both UF and NF are feasible options for the treatment of this effluent, yielding a permeate stream that can be reused in several applications. Finally, 28 pharmaceutical compounds were initially detected in this effluent, and their respective rejection coefficients were determined, with eliminations higher than 75% in the case of NF with the HL membrane. Therefore, it is concluded that NF is an excellent option for the removal of toxic pharmaceuticals in municipal wastewaters.

Air emissions at large municipal wastewater treatment plants in Finland for national E-PRTR reporting register

EC regulation (166/2006) obligates all urban waste water treatment plants above 100.000 PE in European Union area to report their water and air emissions by PRTR protocol from year 2007. There were no general rules or correlations determined to calculate or measure air emissions of municipal wastewater plant. Due to fact that major part of the treatment plants is uncovered, individual air emission study was demanding to implement. In Finland a group of large wastewater treatment plants studied PRTR air emissions based on the samples of Viikinmäki WWTP (780.000 PE), the largest wastewater treatment plant in Finland. Since Viikinmäki WWTP is completely covered, underground plant, ventilation air analyses were possible to implement in full scale. Based on this study, air emissions of Viikinmäki WWTP has been determined and reported to fulfil the PRTR protocol demands. Air emission model was accepted by Finnish Environmental Authorities and the air emission model of Viikinmäki WWTP was used by other, large Finnish WWTPs.

Effectiveness of pilot-scale wetland designs in removing estrogenic compounds from municipal wastewater plant effluent

Discharge from wastewater treatment plants (WWTPs) is a point source for 17-estradiol (E2) and estrone (E1) into surface water systems. This work examines the potential of three pilot-scale wetland designs, a subsurface flow (SSF), a surface flow (SF), and a floating aquatic plant (FAP), to remove E2 and E1 from effluent of a WWTP. None of the three designs completely removed E1 or E2 from the wastewater effluent. Mean E2 and E1 concentrations in the effluent ranged from 32.80 to 55.54 ng/L and 73.60 to 74.80 ng/L, respectively. The SSF design reduced E2 by 27% and the FAP design reduced E2 by 13%. The surface-flow design failed to reduce E2. Effluent E1 concentrations from the different systems were not statistically different from the influent E1 concentration. Adsorption of E2 and chemical transformation of E2 to E1 appears to be the removal mechanisms. An increase in E2 concentrations in the surface-flow system and a decrease of E2 in the FAP system suggest that plants are a factor in the removal of E2. However, evapotranspiration effects complicate the ability to discern the removal mechanism.

Predicting Influent Estradiol and Estrone Concentrations for Wastewater Treatment Facilities

An externally validated model was developed to predict influent concentrations of natural estrogens at municipal wastewater plants. The model kinetic constant for the first-order biotransformation of estradiol into estrone, k(E2), was calculated as 0.030 hour(-1) (ranging from -0.080 to 0.49 hour(-1), with a standard deviation of 0.23) and the model value for the biodegradation k of estrone, k(E1), was -0.18 hour(-1) (ranging from -0.44 to 0.38 hour(-1), with a standard deviation of 0.3). The k values were not found to be temperature-sensitive within the range 12 to 24.5 degrees C and displayed a weak trend of increasing with total suspended solids within the range 0.103 to 0.450 g/L. The new model improved on the predictions of a previous model for influent estrone concentrations, but gave comparable results for estradiol.

A novel laboratory cultivation method to examine antibiotic-resistance-related microbial risks in urban water environments

Although microbial risk due to antibiotic-resistant microbes in water has been a serious public health concern, the current culture-dependent detecting methods using nutrient-rich conditions may not be suitable for evaluating microbial risk. In the present study, a novel cultivation method was developed to detect antibiotic-resistant microbes at various nutrient levels. A nutrient-rich medium Luria-Bertani broth (LB) was diluted at a wide range of dilution factors (10(0)-10(4)) and amended with either tetracycline or vancomycin. A standard environmental cultivation medium, R2A, was also used by amending with antibiotics. The diluted LB with antibiotics was able to detect previously known oligotrophic and antibiotic-resistant bacteria in drinking water and swine manure samples, respectively. These results validate the capability of the new method to detect antibiotic-resistant microbes in various environmental water samples. Using the developed method in assessing microbial risk due to antibiotic-resistant microbes in river and municipal wastewater plants, we found that the viable counts and antibiotic resistance fraction were significantly influenced by the type and concentration level of antibiotic exposure and the cultivation medium conditions. This suggests a further need to standardize cultivation method procedures, to assess microbial risk in water samples.

Wastewater recycling: Application of ozone based treatments to secondary effluents

A secondary effluent from a municipal wastewater plant has been treated by means of several processes based on the use of ozone. Application of O 3 as the only oxidising reagent is capable of halving the initial COD (35 ppm at a flowrate of 40 L h −1) with a roughly 40% of mineralization degree. The system O 3/H 2O 2 slightly enhances COD removal albeit it is capable of significantly increasing the mineralization level up to 70% (35 ppm of O 3 at a flowrate of 40 L h −1 in the presence of 0.01 M of H 2O 2). The combination of two commercial activated carbons and ozone did not improve the results obtained in the single ozonation process. However, the simultaneous application of ozone and UV radiation showed beneficial effects both in the COD removal rate and TOC conversion if compared to ozonation alone. The systems applied in this work can be acceptably modelled by empirical mathematical expressions based on the inlet ozone concentration, hydrogen peroxide concentration, COD, etc.