Municipal Water Resource Recovery Facility Research Articles

β-D-glucuronidase activity triggered monitoring of fecal contamination using microbial and chemical source tracking markers at drinking water intakes

Intense rainfall and snowmelt events may affect the safety of drinking water, as large quantities of fecal material can be discharged from storm or sewage overflows or washed from the catchment into drinking water sources. This study used β-d-glucuronidase activity (GLUC) with microbial source tracking (MST) markers: human, bovine, porcine mitochondrial DNA markers (mtDNA) and human-associated Bacteroidales HF183 and chemical source tracking (CST) markers including caffeine, carbamazepine, theophylline and acetaminophen, pathogens (Giardia, Cryptosporidium, adenovirus, rotavirus and enterovirus), water quality indicators (Escherichia coli, turbidity) and hydrometeorological data (flowrate, precipitation) to assess the vulnerability of 3 drinking water intakes (DWIs) and identify sources of fecal contamination. Water samples were collected under baseline, snow and rain events conditions in urban and agricultural catchments (Québec, Canada). Dynamics of E. coli, HF183 and WWMPs were similar during contamination events, and concentrations generally varied over 1 order of magnitude during each event. Elevated human-associated marker levels during events demonstrated that urban DWIs were impacted by recent contamination from an upstream municipal water resource recovery facility (WRRF). In the agricultural catchment, mixed fecal pollution was observed with the occurrences and increases of enteric viruses, human bovine and porcine mtDNA during peak contaminating events. Bovine mtDNA qPCR concentrations were indicative of runoff of cattle-derived fecal pollutants to the DWI from diffuse sources following rain events. This study demonstrated that the suitability of a given MST or CST indicator depend on river and catchment characteristics. The sampling strategy using continuous online GLUC activity coupled with MST and CST markers analysis was a more reliable source indicator than turbidity to identify peak events at drinking water intakes.

Is removal and destruction of perfluoroalkyl andpolyfluoroalkyl substances from wastewater effluent affordable?

Several jurisdictions are currently evaluating regulatory standards for perfluoroalkyl and polyfluoroalkyl substances (PFAS) in municipal water resource recovery facility (WRRF) effluent. Effective and responsible implementation of PFAS effluent limits should consider the costs and capabilities of currently available technologies, because the costs of meeting WRRF PFAS limits could disproportionally fall to ratepayers. Cost curves were developed for currently available PFAS separation and destruction options, assuming effluent treatment targets near current analytical detection limits. Removing and destroying PFAS from municipal WRRF effluent is estimated to increase costs per household by a factor of between 2 and 210, using Minnesota-specific data as an example. Estimated costs per household would increase more for residents of smaller communities, averaging 33% of median household income (MHHI) in communities smaller than 1000 people. This exceeds the U.S. Environmental Protection Agency (EPA)-developed affordability index of 2% of MHHI by a factor of 16. Estimated costs per household to remove and destroy PFAS varied among locations, primarily based on WRRF and community size, median income, rural versus urban, and type of wastewater treatment processes currently used. PRACTITIONER POINTS: Required tertiary treatment before WRRF effluent PFAS separation, using currently available technologies, is a significant portion (~40-80%) of estimated costs. Adding PFAS separation, destruction, and pre-treatment would make Minnesota wastewater rates unaffordable (defined by EPA affordability guidance) without external funding. The estimated cost per household is higher for smaller communities and would require substantial external funding to maintain rate affordability. Design and operating uncertainties remain for full-scale WRRF retrofits to consistently remove and destroy effluent PFAS with limited full-scale applications.

Removal of emerging micropollutants from nanofiltration retentate of municipal wastewater within biological fixed-bed reactors under nitrifying and denitrifying conditions.

Municipal water resource recovery facilities are not designed to eliminate micropollutants, leading to many pollutants entering the aquatic environment. Within this study, as part of the project MicroStop, the biological treatment of nanofiltration effluent (retentate) under pure aerobic (without nitrification) as well as nitrifying and denitrifying conditions has been investigated for micropollutant elimination. A potential of further biotransformation under increased hydraulic retention time (HRT) of 14 days was shown. Under both HRT of 7 and 14 days, eliminations below LOQ were achieved in the aerated bioreactor for gabapentin, iomeprol, and metoprolol, reaching > 95%, > 69 to > 92%, and > 72%, respectively. The reduction of diclofenac was positively influenced by longer HRT leading to an elimination of up to 67%. Sulfamethoxazole was reduced under denitrification, but accumulated under aeration, resulting in fluctuating results and an overall elimination of 78% under 14 days HRT. PRACTITIONER POINTS: The micropollutant elimination in fixed-bed bioreactors of highly concentrated nanofiltration retentate was studied. Pure aerobic (without nitrification), nitrifying, and denitrifying conditions were investigated under hydraulic retention times (HRT) of 7 and 14 days. Higher initial pollutant concentrations enhanced the biological degradability in attached growth for substances being moderately degradable in activated sludge systems. 4A potential of further biological micropollutant elimination was shown for gabapentin, iomeprol, metoprolol, and diclofenac.

The microbiome of two strategies for ammonia removal with the sequencing batch moving bed biofilm reactor treating cheese production wastewater.

Cheese production facilities must abide by sewage discharge bylaws that prevent overloading municipal water resource recovery facilities, eutrophication, and toxicity to aquatic life. Compact treatment systems can permit on-site treatment of cheese production wastewater; however, competition between heterotrophs and nitrifiers impedes the implementation of the sequencing batch moving bed biofilm reactor (SB-MBBR) for nitrification from high-carbon wastewaters. This study demonstrates that a single SB-MBBR is not feasible for nitrification when operated with anerobic and aerobic cycling for carbon and phosphorous removal from cheese production wastewater, as nitrification does not occur in a single reactor. Thus, two reactors in series are recommended to achieve nitrification from cheese production wastewater in SB-MBBRs. These findings can be applied to pilot and full-scale SB-MBBR operations. By demonstrating the potential to implement partial nitrification in the SB-MBBR system, this study presents the possibility of implementing partial nitrification in the SB-MBBR, resulting in the potential for more sustainable treatment of nitrogen from cheese production wastewater.

Biochar integrated reactive filtration of wastewater for P removal and recovery, micropollutant catalytic oxidation, and negative CO2 e: Process operation and mechanism.

Biochar (BC) use in water treatment is a promising approach that can simultaneously help address societal needs of clean water, food security, and climate change mitigation. However, novel BC water treatment technology approaches require operational testing in field pilot-scale scenarios to advance their technology readiness assessment. Therefore, the objective of this study is to evaluate the system performance of BC integrated into hydrous ferric oxide reactive filtration (Fe-BC-RF) with and without catalytic ozonation (CatOx) process in laboratory and field pilot-scale scenarios. For this investigation, Fe-BC-RF and Fe-CatOx-BC-RF pilot-scale trials were conducted on synthetic lake water variants and at three municipal water resource recovery facilities (WRRFs) at process flows of 0.05 and 0.6L/s, respectively. Three native and two iron-modified BCs were used in these studies. The commercially available reactive filtration process (Fe-RF without BC) had 96%-98% total phosphorus (TP) removal from 0.075- and 0.22-mg/L TP, as orthophosphate process influent in these trials. With BC integration, phosphorus removal yielded 94%-98% with the same process-influent conditions. In WRRF field pilot-scale studies, the Fe-CatOx-BC-RF process removed 84%-99% of influent total phosphorus concentrations that varied from 0.12 to 8.1 mg/L. Nutrient analysis on BC showed that the recovered BC used in the pilot-scale studies had an increase in TP from its native concentration, with the Fe-amended BC showing better P recovery at 110% than its unmodified state, which was 16%. Lastly, the field WRRF Fe-CatOx-BC-RF process studies showed successful destructive removals at >90% for more than 20 detected micropollutants, thus addressing a critical human health and environmental water quality concern. The research demonstrated that integration of BC into Fe-CatOx-RF for micropollutant removal, disinfection, and nutrient recovery is an encouraging tertiary water treatment technology that can address sustainable phosphorus recycling needs and the potential for carbon-negative operation. PRACTITIONER POINTS: A pilot-scale hydrous ferric oxide reactive sand filtration process integrating biochar injection typically yields >90% total phosphorus removal to ultralow levels. Biochar, modified with iron, recovers phosphorus from wastewater, creating a P/N nutrient upcycled soil amendment. Addition of ozone to the process stream enables biochar-iron-ozone catalytic oxidation demonstrating typically excellent (>90%) micropollutant destructive removals for the compounds tested. A companion paper to this work explores life cycle assessment (LCA) and techno-economic analysis (TEA) to explore biochar water treatment integrated reactive filtration impacts, costs, and readiness. Biochar use can aid in long-term carbon sequestration by reducing the carbon footprint of advanced water treatment in a dose-dependent manner, including enabling an overall carbon-negative process.

Exploring Anaerobic Digestion from Mesophilic to Thermophilic Temperatures—Operational and Microbial Aspects

Digesters at water resource recovery facilities (WRRFs) operating at different temperatures within the mesophilic and thermophilic temperature range is a flexibilization concept to contribute to heat management. Four 25 L digesters were fed with sewage sludge from a municipal WRRF and were operated at 37, 43, 47 and 53 °C, respectively, to describe changes in the overall process performance and the microbiota. Specific methane yield and COD degradation rates were the highest at 47 °C, only being up to 7% higher compared with at 37 °C. The increase in pH and concentrations of NH4-N and PO4-P above 43 °C were statistically significant. The effect on the microbial community was strong, indicating both a constant specialization towards thermophilic organisms as well as a change from acetoclastic to hydrogenotrophic/methylotrophic methanogenesis. The influence of temperature on process-engineering and physicochemical aspects was rather small compared with the changes in the microbiota.

Large-scale micro-aerobic digestion studies at municipal water resource recovery facilities for process-integrated biogas desulfurization

Biogas generated from anaerobic digestion processes typically requires gas conditioning including hydrogen sulfide removal before it is used on-site to generate electricity and heat or before upgrading to biomethane for gas pipeline distribution or vehicle fuel. Experiments of process-integrated micro-aeration in three different large-scale sludge digesters (effective volume 2450 m3, 3250 m3 and 3300 m3) were undertaken at municipal wastewater treatment plants and compared with large-scale applications reported in literature. This work discusses critical process parameters, advantages, and potential limitations of micro-aerobic digestion in comparison with other commonly used biogas desulfurization methods. It shows that high H2S reduction in the biogas can be obtained and that the H2S reduction is dependent not only on the air injection rate and location, but also on the digestion activity identified by the volumetric biogas production. Reliability testing of typical micro-aerobic upset scenarios and long-term micro-aerobic digester operation as part of this study provided deeper insights in the MA process that could also provide valuable input to what operational, maintenance and safety measures should be considered when applying micro-aeration in large-scale digesters. The large-scale micro-aerobic digestion trials demonstrated that the hydrogen sulfide concentration in the biogas can be controlled using minimal plant upgrades, contributing to the sustainability and economic efficiency of the energy recovery process of waste sludge digestion at water resource recovery facilities.

Characterization of antibiotic resistance genes and bacteria in a municipal water resource recovery facility.

Municipal water resource recovery facilities (WRRFs) are important sources of antibiotic-resistant bacteria and genes (ARB and ARGs). In this study, antibiotic-resistant total heterotrophic bacteria (THBR ) counts (CFU/ml) cultivated from influent, effluent of activated sludge process, and outflow of disinfection unit of an urban WRRF were investigated for the presence of 16, 32, 64, and 128 μg/ml of nine antibiotics. The isolates of Pseudomonas spp., Acinetobacter spp., and Escherichia coli obtained from effluent of activated sludge process were subjected for molecular identification by detecting the 16S rRNA gene sequences. Additionally, using the polymerase chain reaction method (PCR), the isolates were investigated for the presence of blaSHV , blaTEM , blaCTX-M , blaVIM , sul1, and qnrS genes. According to the results, the abundance of THBR counts was not significantly reduced by the biological treatment except for cefixime and sulfamethoxazole; it also increased for some antibiotics after disinfection unit. The average removal efficiency of THBR resistant to ciprofloxacin, sulfamethoxazole, and ceftazidime were 7.9±1.7%, 41.8±2.1%, and 14.4±6.2%, respectively. Also, all the tested isolates were resistant to at least four antibiotics. For all antibiotics, the resistance ratio (THBR /THB) significantly increased in the effluent and after chlorination unit. Among 12 resistant isolates, blaTEM and sul1 genes were the most frequently detected ones involved in 92% and 83% of the isolates, respectively. Both blaTEM and sul1 genes were found in 100% of E.coli, and 83% and 67% of Pseudomonas spp. isolates, respectively. Further efforts are necessary to limit the transmission of ARB and ARGs from WRRFs into the environment and prevent human health threats. PRACTITIONER POINTS: The ratio of resistance significantly increased after biological treatment. Up to 40% of heterotrophic bacteria in the effluent was antibiotic resistant. blaTEM and sul1 genes were more prevalent (92%) in all isolates of bacteria. Both blaTEM and sul1 genes were found in 100% of E. coli isolates. Pseudomonas spp. holds blaTEM and sul1 genes in 83% and 67% of isolates, respectively.

Release of poly- and perfluoroalkyl substances from finished biosolids in soil mesocosms

Finished biosolids were collected and characterized from seven municipal water resource recovery facilities. Poly- and perfluoroalkyl substances (PFAS) for the 54 quantified in the biosolids ranged from 323 ± 14.1 to 1100 ± 43.8 µg/kg (dry weight basis). For all biosolids, greater than 75% of the PFAS fluorine mass was associated with precursors. Di-substituted polyfluorinated phosphate esters (diPAPs) were the most abundant PFAS identified in the biosolids. The total oxidizable precursor assay on biosolids extracts generally failed to quantify the amount of precursors present, in large part due to the fact that diPAPS were not fully transformed during the TOP assay. Outdoor biosolids column leaching experiments intended to simulate biosolids land application showed sustained PFAS leaching over the 6-month study duration. Perfluoroalkyl acid (PFAA) concentrations in leachate, when detected, typically ranged in the 10 s to 100 s of ng/L; no diPAPs were detected in the leachate. The PFAA leaching from the biosolids exceeded the PFAA mass initially present in the biosolids (typically by greater than an order of magnitude), but the cumulative PFAA mass leached did not exceed the molar equivalents that could be explained by transformation of quantified precursors. These results highlight the importance of PFAA precursors initially present in biosolids and their contribution to long term leaching of PFAAs from land-applied biosolids.

Assessment of the significance of heavy metals, pesticides and other contaminants in recovered products from water resource recovery facilities

The recovery of valuable materials from municipal water resource recovery facilities (WRRF) is a promising option to implement circular economy in wastewater treatment. Different technologies are being evaluated at different WRRF to recover products such as struvite, bioplastics and cellulose. However, the quality of these recovered products remains to be assessed in terms of their possible contamination with various hazardous compounds that may compromise their application in agriculture or construction. The aim of this article is therefore to assess the quality of products recovered from various recovery techniques implemented at demonstration sites. The results obtained for heavy metals, pesticides, chloroalkanes and PAHs from the analysis of 15 recovered products are reported and compared to the closest regulation framework possible. In general, the results showed that the products met current regulations and only some of them slightly exceeded the limits for very specific pollutants and only for a specific use, such as the food industry. These results are promising to accelerate the market penetration of these recovered products. However, this work highlights the need for a novel regulatory framework for these products that fits with its current uses.

Efficacies of Nitrogen Removal and Comparisons of Microbial Communities in Full-Scale (Pre-Anoxic Systems) Municipal Water Resource Recovery Facilities at Low and High COD:TN Ratios

At a low COD:TN ratio (≤5) in influent, maintaining a longer HRT (≥9 h) and longer SRT (≥30 d) are suggested to improve higher N removal efficiency in case of operation at low DO (Dissolved oxygen) level (0.9 ± 0.2 mg-O2/L). However, in case of operation at high DO level (4.0 ± 0.5 mg-O2/L), short HRT (1 h) and typical SRT (17 d) make it possible to achieve nitrogen removal. On the other hand, at a high COD:TN ratio (≥8.4), a typical HRT (9–15 h), SRT (12–19 d), and DO level (1.3–2.6 mg-O2/L) would be applied. Microbial distribution analysis showed an abundance of AOA (Ammonia-oxidizing archaea) under conditions of low DO (≤0.9 mg-O2/L). Nitrosomonas sp. are mostly found in the all investigated water resource recovery facilities (WRRFs). Nitrosospira sp. are only found under operating conditions of longer SRT for WRRFs with a low COD:TN ratio. In comparison between abundances of Nitrobacter sp. and Nitrospira sp., abundances of Nitrobacter sp. are proportional to low DO concentration rather than abundance of Nitrospira sp. A predominance of nosZ-type denitrifiers were found at low DO level. Abundance of denitrifiers by using nirS genes showed an over-abundance of denitrifiers by using nirK genes at low and high COD:TN ratios.

Fate of cellulose in primary and secondary treatment at municipal water resource recovery facilities.

Cellulose from toilet paper is a significant fraction of particulate organics, which is recoverable. For the first time, comprehensive mapping and tracking the fate of cellulose across various unit processes at full-scale in two water resource recovery facilities located in North America and Europe was undertaken. The influent cellulose content accounted for approximately one-third of the total suspended solids (TSS). Although about 80% of the raw wastewater cellulose was removed in primary treatment, the type of primary treatment process (rotating belt filter [RBF] vs. primary clarification [PC]) had a significant impact on cellulose capture and diversion. The high cellulose content of the RBF sludge accounting for 35% of the TSS facilitates cellulose recovery. For the North American plant, with a conventional activated sludge process (SRT of 6-7days, preceded by PC), cellulose biodegradation efficiencies of 70%-90% of the PC effluent were observed in summer and winter. For the European plant, with a modified University of Cape Town process (SRT of 14days, without primary treatment in train 2, or preceded by RBF in train 1), comparable cellulose biodegradation efficiencies were also observed. Results from laboratory SBRs indicated that cellulose biodegradation efficiency at room temperature was 86% of the influent cellulose. PRACTITIONER POINTS: Cellulose fate was tracked across two different WWTPs in two different geographies. Cellulose in the influent wastewater accounted for 1/3 of the total suspended solids. Primary treatments were able to capture more than 80% of the influent cellulose. Cellulose was biodegraded in secondary treatment, resulting an effluent of 2-3mg/L.

Laccase removal of 2-chlorophenol and sulfamethoxazole in municipal wastewater.

Laccases were studied for their ability to remove two compounds, 2-chlorophenol and sulfamethoxazole, in batch studies, both in buffered solutions and in wastewater samples from different points in a municipal water resource recovery facility. Two enzymes with and without a mediator (acetosyringone) were investigated: a commercial product derived from Myceliphthora thermophile and a laboratory-generated enzyme mix derived from Tramates versicolor. The chlorophenol was removed rapidly by the commercial enzyme in the presence of acetosyringone, but the primary products were coupling complexes of the reactants. Excellent removal was achieved without acetosyringone by the natural enzyme mix. Sulfamethoxazole was poorly removed in all laboratory-generated chemically buffered solutions, but was very well removed, without the addition of mediators, in secondary effluent suspensions from a municipal water resource recovery facility. Mechanistic studies are still required, but the results suggest that treatment via direct addition of enzymes is feasible to remove recalcitrant compounds in municipal wastewater.

A pilot-scale deep bed denitrification filter for secondary effluent treatment using sodium acetate as external carbon.

A pilot-scale quartz sand deep bed denitrification filter (DBDF) using sodium acetate as the additional carbon source was implemented to treat secondary effluent, with a high nitrate nitrogen (NO3 -N) concentration and low C/N ratio, from an urban municipal water resource recovery facility. By the 18th day, results showed that the removal efficiency of NO3 -N and the chemical oxygen demand (COD) were stable at above 85% and 70%, respectively. When the filter layer depth was set to 1,600mm and the concentration of additional sodium acetate was maintained at 51mg/L, the total nitrogen and COD concentrations of the DBDF effluent were stabilized below 5 and 30mg/L, respectively. The quartz sand DBDF had a good effect on the removal of dissolved organic matter, especially for aromatic protein-like and tryptophan protein-like substances. Bacteria with denitrification function, such as Cloacibacterium and Zoogloea, became increasingly dominant with increasing filling layer depth. PRACTITIONER POINTS: The denitrification filter had a good effect on the removal of aromatic protein-like and tryptophan protein-like substances. Cloacibacterium and Zoogloea became increasingly dominant with increasing filling layer depth.

A Comparison of Heterogeneous/Homogeneous Crystallization for Phosphate Recovery from Biosolids

In this study, a fluidized bed reactor was used to compare heterogeneous and homogeneous crystallization for recovering magnesium ammonia phosphate (MAP) from the dewatering filtrate at a municipal water resource recovery facility. Investigating the factors affecting crystallization revealed that pH exerted a greater effect than the Mg/P molar ratio. The results of a heterogeneous crystallization experiment showed that removal efficiency of phosphate (RP%) and crystal efficiency of phosphate (CP%) were 68% and 66%, respectively, at a PO4 -P concentration of 200 mg/L, pH of 8.0, and Mg/P molar ratio of 1.0 for 3 h. The reaction rate of heterogeneous crystallization was markedly higher than that of homogeneous crystallization. Those pellets produced through the heterogeneous crystallization exhibited a dense surface (particle size 0.5-1.0 mm; water content 8.7%). Through scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and X-ray diffraction (XRD) examination, the crystallized patterns of the needle-shaped pellets were identified as MgNH4 PO4 ·6H2 O. This article is protected by copyright. All rights reserved.

CO2 and N2O from water resource recovery facilities: Evaluation of emissions from biological treatment, settling, disinfection, and receiving water body

Water resource recovery facilities (WRRFs) contribute to climate change and air pollution, as they are anthropogenic potential sources of direct and indirect emission of greenhouse gases (GHGs). Studies concerning the monitoring and accounting for GHG emissions from WRRFs are of increasing interest. In this study, the floating hood technique for gas collection was coupled with the off-gas method to monitor and apportion nitrous oxide (N2O) and carbon dioxide (CO2) emissions from both aerated and non-aerated tanks in a municipal water resource recovery facility, in order to investigate its carbon footprint (CFP). To our knowledge, this is the first time that the chamber technique was applied to evaluate gas fluxes from the settler, where an emission factor (EF) of 4.71 ∗ 10−5 kgCO2,eq kgbCOD−1 was found. Interesting results were found in the disinfection unit, which was the major contributor to direct N2O emissions (with a specific emission factor of 0.008 kgCO2,eq kgbCOD−1), due to the chemical interaction between hydroxylamine and the disinfectant agent (hypochlorite). The specific emission factor of the biological aerated tank was 0.00112 kgCO2,eq kgbCOD−1. The average direct CO2 emission was equal to 0.068 kgCO2 kgbCOD−1 from the activated sludge tank and to 0.00017 kgCO2 kgbCOD−1 from the secondary clarifier. Therefore, taking into account the contribution of both direct N2O and CO2 emissions, values of 0.069 kgCO2,eq kgbCOD−1, 0.008 kgCO2,eq kgbCOD−1 and 0.00022 kgCO2,eq kgbCOD−1, were found for the net CFP of the aerated compartment, the disinfection unit and the clarifier, respectively.The plant energy Footprint (eFP) was also evaluated, confirming that the aeration system is the major contributor to energy consumption, as well as to indirect CO2 emission, with a specific eFP of 1.49 kWh kgbCOD−1.

Fate and inhibitory effect of silver nanoparticles in high rate moving bed biofilm reactors

Municipal water resource recovery facilities are the primary recipients of a significant fraction of discharged silver nanoparticle (AgNP)-containing wastes, yet the fate and potential risks of AgNPs in attached-growth biological wastewater treatment processes are poorly understood. The fate and inhibitory effects of polyvinylpyrrolidone (PVP)-coated AgNPs at environmentally-relevant nominal concentrations (10, 100, 600 μg/L) were investigated, for the first time, in high rate moving bed biofilm reactors (MBBRs) for soluble organic matter removal. The behavior and removal of continuously added AgNPs were characterized using single-particle inductively coupled plasma mass spectrometry (spICP-MS). While no inhibitory effect at average influent concentration of 10.8 μg/L Ag was observed, soluble COD removal efficiency was significantly decreased at 131 μg/L Ag in 18 days and 631 μg/L Ag in 5 days with suppressed biofilm viability. The inhibitory effect of AgNPs on treatment efficiency was highly correlated to the retained mass of total Ag in attached biofilm on the carriers. Biofilm demonstrated limited retention capacity for AgNPs over 18 days. Considerable mass of Ag (38% to 75%) was released via effluent, predominantly as NPs. We detected some chemically transformed and potentially less toxic forms of silver nanoparticles (Ag2S, AgCl), over the exposure period. This study demonstrated the distinct interaction dynamics, bioavailability and inhibitory effects of AgNPs in a biofilm system. Release of bioavailable AgNPs via effluent and AgNP-rich biofilm, sloughing off the carriers, can affect the treatment chain efficiency of downstream processes. Thus, the inhibitory effects of AgNPs can be a concern even at concentrations as low as 100 to 600 μg/L Ag in biological attached growth wastewater treatments.

FOG Waste receiving and processing facility design considerations

Abstract Fats, Oils, and Grease (FOG) wastes and high-strength wastes (HSW) are frequently received at municipal water resource recovery facilities (WRRFs) as trucked-in wastes. These wastes offer significant benefits in terms of revenue from tipping fees and feedstock for co-digestion in anaerobic digesters that produce biogas, which can be beneficially used as fuel. The number of treatment plants receiving and beneficially using trucked-in wastes currently in operation or under investigation is increasing rapidly across the North America as utilities strive to remove this material from normal wastewater to avoid sewer system clogging, maintenance and backups, avoid the oxygen demand of these wastes in secondary treatment systems, and to capture and beneficially reuse the energy that is contained within the material. Historically, trucked-in wastes have been discharged to the head end of treatment plants or to an upstream manhole in the incoming interceptor sewer to enable the material to be mixed with raw wastewater prior to treatment through the liquid stream of the WRRF. However, this approach results in loss of material and degradation of the energy value of the FOG wastes and HSW and also creates collection and maintenance issues in the preliminary and primary treatment systems. To prevent degradation of the material and retain maximum energy for the CHP system, receiving stations are being constructed for direct off-loading of the wastes to processing and storage facilities prior to their transfer to anaerobic digesters at a relatively uniform rate to minimize the potential for digester upsets while at the same time to increase biogas production. This paper presents the key components and considerations in the design and operation of modern FOG waste receiving and processing facilities.

Pretreatment and Anaerobic Co-digestion of Selected PHB and PLA Bioplastics

Conventional petroleum-derived plastics are recalcitrant to biodegradation and can be problematic as they accumulate in the environment. In contrast, it may be possible to add novel, biodegradable bioplastics to anaerobic digesters at municipal water resource recovery facilities along with primary sludge to produce more biomethane. In this study, thermal and chemical bioplastic pretreatments were first investigated to increase the rate and extent of anaerobic digestion. Subsequently, replicate, bench-scale anaerobic co-digesters fed synthetic primary sludge with and without PHB bioplastic were maintained for over 170 days. Two polyhydroxybutyrate (PHB), one poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and one polylactic acid (PLA) bioplastic were investigated. Biochemical methane potential (BMP) assays were performed using both untreated bioplastic as well as bioplastic pretreated at elevated temperature (35 to 90°C) under alkaline conditions (8<pH<12) for 3 to 48 h. PHB and PLA pretreatment increased average BMP values up to over 100 %. Average PHB lag time before methane production started decreased when pretreatment was performed. Bench-scale anaerobic co-digesters fed synthetic primary sludge with PHB bioplastic resulted in 80 to 98% conversion of two PHB bioplastics to biomethane and a 5% biomethane production increase at the organic loadings employed (sludge OLR=3.6 g COD per L of reactor volume per day [g COD/ LR-d]; bioplastic OLR = 0.75 g theoretical oxygen demand per L of reactor volume per day [ThOD/LR-d]) compared to digesters not fed bioplastics. Anaerobic digestion or co-digestion is a feasible management option for biodegradable plastics.

A taxonomy of chemicals of emerging concern based on observed fate at water resource recovery facilities

As reuse of municipal water resource recovery facility (WRRF) effluent becomes vital to augment diminishing fresh drinking water resources, concern exists that conventional barriers may prove deficient, and the upcycling of chemicals of emerging concern (CECs) could prove harmful to human health and aquatic species if more effective and robust treatment barriers are not in place. A multiple month survey, of both primary and secondary effluents, from three (3) WRRFs, for 95 CECs was conducted in 2014 to classify CECs by their persistence through conventional water reclamation processes. By sampling the participating WRRF process trains at their peak performance (as determined by measured bulk organics and particulates removal), a short-list of recalcitrant CECs that warrant monitoring to assess treatment performance at advanced water reclamation and production facilities. The list of identified CECs for potable water reclamation (indirect or direct potable reuse) include a herbicide and its degradants, prescription pharmaceuticals and antibiotics, a female hormone, an artificial sweetener, and chlorinated flame retardants.