Metropolitan Wastewater Treatment Plant Research Articles

Plant-wide modeling of a metropolitan wastewater treatment plant to reduce energy consumption and carbon footprint.

A real metropolitan wastewater treatment plant (RWWTP) serving a population equivalent of 1.55 million was modeled to reduce energy consumption and carbon footprint (CFP). An approach was proposed to handle the dilution factor and partial aeration due to discontinuous air diffuser locations in the Bardenpho-5 configuration. Various operational, structural, and configurational modifications were evaluated. Results indicated that management scenarios might provide conflicting outcomes for different targets. Reduced energy consumption may not result in lower CFP at the same time. Moreover, operational changes that would impact total nitrogen (TN) concentrations and N2O release may significantly impact CFP. A policy of using a modified Bardenpho-5 process with reduced internal recycle (IR) ratio, waste activated sludge (WAS), and return activated sludge (RAS) flow rates provided the lowest CPF. Modified Bardenpho-5 process and replacing belt thickeners with gravity thickeners supplied the highest savings in energy consumption. Overall, up to 14% and 20% reductions were possible in the energy consumption and CFP of the plant, respectively. The RWWTP may save up to 10% in energy expenses annually by operational modifications.

Wastewater surveillance of SARS-CoV-2 mutational profiles at a university and its surrounding community reveals a 20G outbreak on campus.

Wastewater surveillance of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been leveraged during the Coronavirus Disease 2019 (COVID-19) pandemic as a public health tool at the community and building level. In this study, we compare the sequence diversity of SARS-CoV-2 amplified from wastewater influent to the Columbia, South Carolina, metropolitan wastewater treatment plant (WWTP) and the University of South Carolina campus during September 2020, which represents the peak of COVID-19 cases at the university during 2020. A total of 92 unique mutations were detected across all WWTP influent and campus samples, with the highest frequency mutations corresponding to the SARS-CoV-2 20C and 20G clades. Signature mutations for the 20G clade dominated SARS-CoV-2 sequences amplified from localized wastewater samples collected at the University of South Carolina, suggesting that the peak in COVID-19 cases during early September 2020 was caused by an outbreak of the 20G lineage. Thirteen mutations were shared between the university building-level wastewater samples and the WWTP influent collected in September 2020, 62% of which were nonsynonymous substitutions. Co-occurrence of mutations was used as a similarity metric to compare wastewater samples. Three pairs of mutations co-occurred in university wastewater and WWTP influent during September 2020. Thirty percent of the detected mutations, including 12 pairs of concurrent mutations, were only detected in university samples. This report affirms the close relationship between the prevalent SARS-CoV-2 genotypes of the student population at a university campus and those of the surrounding community. However, this study also suggests that wastewater surveillance at the building-level at a university offers important insight by capturing sequence diversity that was not apparent in the WWTP influent, thus offering a balance between the community-level wastewater and clinical sequencing.

Disproportionate Changes in Composition and Molecular Size Spectra of Dissolved Organic Matter between Influent and Effluent from a Major Metropolitan Wastewater Treatment Plant

Dynamic changes in the abundance, composition, and size spectra of dissolved organic matter (DOM) in different size-fractions between influent and effluent from Milwaukee metropolitan wastewater treatment plants (WWTPs) were evaluated using size-fractionation, excitation–emission matrix (EEM) coupled with parallel factor analysis (PARAFAC), and ΔEEM approaches. Up to 82.7% of DOC, 43.1% of total dissolved nitrogen (TDN), and 52.4% of chromophoric-DOM (CDOM) were removed from the influent, indicating different reactivity/degrability and disproportionate removal between DOM species. Within the CDOM pool, both the aromaticity and humification-index increased after treatments while the biological-index remained similar, showing a preferential removal of autochthonous DOM and the protein-like components, resulting in a higher abundance of humic-like components in the effluent but little change in the DOM size spectra. Up to 3%–5% differences were measured in the bulk DOM concentrations between the 0.22 and 0.7 μm filtrates. In addition, DOM in the 0.22–0.7 μm size-fraction contained almost only protein-like components, showing a high DOM heterogeneity. High levels of photochemically and biologically labile DOM in the effluent, with a higher molecular weight and lower DOC/TDN ratio, may alter the microbial community and biogeochemical processes in coastal Lake Michigan. Long-term and concurrent characterization of DOM in both effluent and receiving waters is needed to better understand the environmental/ecological roles of DOM as it moves through WWTPs and into the natural environment.

Pulsed electric field application reduces carbapenem- and colistin-resistant microbiota and blaKPC spread in urban wastewater

Wastewater flows from metropolitan areas, especially those with healthcare inputs, can serve as transport reservoirs for the dissemination of clinically-relevant antimicrobial resistant bacteria (ARB) such as carbapenem- (CR) and colistin-resistant (CoR) strains. Pulsed electric field (PEF) is an emerging wastewater management tool for reducing bacterial loads without generating environmentally harmful byproducts, but it's ability to reduce ARB and their genetic determinants is not well reported. We collected 86, 10-L raw wastewater influent samples from a large metropolitan wastewater treatment plant in Columbus, Ohio and subjected them to low (34 kV cm−1 for 67 μsec) and high (36 kV cm−1 for 89 μsec) PEF treatment. We quantified the PEF effectiveness by measuring concentrations of total coliform bacteria, CR and CoR bacteria, and the epidemic carbapenemase gene, blaKPC, before and after PEF treatment. Utilizing marginal linear regression models with generalized estimating equations, we observed that low and high PEF treatment resulted in a 1.94 (95% CI 2.06–1.81; P < 0.001) and 2.32 (95% CI 2.46–2.18; P < 0.001) log reduction of total coliform bacteria concentrations, respectively. Low and high PEF treatment produced similar log reductions between CR E. coli (2.01 (95% CI 2.15–1.86; P < 0.001); 2.14 (95% CI: 5.30–4.61; P < 0.001)) and CR Enterobacteriaceae concentrations (1.55 (95% CI 1.70–1.41; P < 0.001); 1.86 (95% CI 2.05–1.68; P < 0.001)), and resulted in a 1.15 log (95% CI 1.38–0.93, P < 0.001) and 1.28 log (95% CI 1.54–1.03, P < 0.001) reduction of absolute blaKPC concentrations. Log CoR E. coli concentrations were reduced by 2.47 (95% CI 2.78–2.15; P < 0.001) and 2.52 (95% CI 2.91–2.15; P < 0.001) and CoR Enterobacteriaceae by 2.24 (95% CI 2.52–1.95; P < 0.001) and 2.50 (95% CI 2.89–2.11; P < 0.001) following low and high PEF application. PEF can be applied for wastewater management as an independent treatment method, particularly at critical control points, such as an on-site management of wastewater from hospitals or other healthcare facilities, or in series with other conventional methods to reduce total bacterial loads and concentrations of clinically-relevant ARB.

Full-scale investigation of ferrous dosing in sewers and a wastewater treatment plant for multiple benefits

This study demonstrates the full scale application of iron dosing in a metropolitan wastewater treatment plant (WWTP) and the upstream sewer system for multiple benefits. Two different dosing locations, i.e., the WWTP inlet works (Trial-1) and upstream sewer network (Trial-2) were tested in this study. Both dosing trials achieved multiple benefits such as sulfide control, phosphate removal and improved sludge dewaterability. During Trial-1, a sulfide reduction of >90% was achieved at high dosing rates (>19 kgFe ML−1) of ferrous chloride in the inlet works and in Trial-2 the in-sewer ferrous dosing had significant gas phase hydrogen sulfide (H2S) concentration reduction in the sewer network. The ferrous dosing enhanced the phosphate removal in the bioreactor up to 76% and 53 ± 2% during Trial-1 & 2, respectively. The iron ending up in the anaerobic sludge digester reduced the biogas H2S concentration by up to 36% and 45%, respectively. The dewaterability of the digested sludge was improved, with relative increases of 9.7% and 9.8%, respectively. The presence of primary clarifier showed limited impact on the downstream availability of iron for achieving the afore-mentioned multiple benefits. The iron dosing enhanced the total chemical oxygen demand removal in the primary clarifier reaching up to 49% at the high dose rates during Trial-1 and 42 ± 1% during Trial-2. This study demonstrated that multiple benefits could be achieved independent of the iron dosing location (i.e., at the WWTP inlet or in the network). Further, iron dosing at both locations enhances primary settling, beneficial for bioenergy recovery from wastewater.

A sensitive analytical method for the measurement of neurotransmitter metabolites as potential population biomarkers in wastewater

Wastewater-based epidemiology is a growing research field which provides valuable information on community drug use and chemical exposure. One parameter critical to estimations of drug use is the catchment area population. A population biomarker could be used to provide this information. This study evaluated the analytical suitability of three endogenous biomarkers of human activity: the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) which has previously been proposed and two further candidates, the catecholamine metabolites vanillylmandelic acid (VMA) and homovanillic acid (HVA). An analytical method involving derivatization was developed and validated for two candidates, 5-HIAA and HVA by liquid chromatography – mass spectrometry. The best performance was obtained for VMA as the underivatized analyte. The derivatized extracts produced a 100 times better sensitivity. The three neurotransmitter metabolites were evaluated as population biomarkers in wastewater samples. All were stable in sample, not lost upon filtration and showed stable inter-day mass loads over seven days for a metropolitan wastewater treatment plant. When applied to a small community during a festival period, mass loads of both HVA and VMA reflected the increase in the catchment population, whilst 5-HIAA proved to be more variable.

Understanding the Removal and Fate of Selected Drugs of Abuse in Sludge and Biosolids from Australian Wastewater Treatment Operations

Abstract Illicit and pharmaceutical drugs are considered to be emerging contaminants of concern, and much research effort has gone into assessing their occurrence in wastewater. However, little information exists on their presence in treated sludge or biosolids. In this study, we examined sludge and biosolids from a large metropolitan wastewater treatment plant (WWTP) in Australia to determine the occurrence of five drugs of abuse, including benzoylecgonine as indicator of cocaine consumption, methamphetamine and 3,4-methylenedioxy methamphetamine (MDMA) as representative illicit stimulants, and codeine and morphine as pharmaceuticals with potential environmental risk. The samples were solid-phase extracted and analyzed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). Benzoylecgonine and MDMA were present in raw sludge but were notably degraded during solids treatment processes, and were not detected in the dewatered sludge (after treatment) or in biosolids. Methamphetamine, codeine, and morphine were detected in all biosolids samples at mean concentrations of 20–50 μg·kg−1. The presence of these three drugs in biosolids shows that these compounds are relatively stable in the solids and in soil, and can persist in biosolids for at least several years. A simple environmental risk assessment based on estimated risk quotients (RQs) for these compounds indicated that the potential environmental risks associated with the land application of biosolids are very low at typical Australian biosolids application rates.

Carbapenemase-producing Enterobacteriaceae and Aeromonas spp. present in wastewater treatment plant effluent and nearby surface waters in the US.

Carbapenemase-producing bacteria (CPB) are rare, multidrug resistant organisms most commonly associated with hospitalized patients. Metropolitan wastewater treatment plants (WWTP) treat wastewater from large geographic areas which include hospitals and may serve as epidemiologic reservoirs for the maintenance or expansion of CPB that originate from hospitals and are ultimately discharged in treated effluent. However, little is known about the potential impact of these WWTP CPB on the local surface water and their risk to the public health. In addition, CPB that are present in surface water may ultimately disseminate to intensively-managed animal agriculture facilities where there is potential for amplification by extended-spectrum cephalosporins. To better understand the role of WWTPs in the dissemination of CPB in surface waters, we obtained samples of treated effluent, and both upstream and downstream nearby surface water from 50 WWTPs throughout the US. A total of 30 CPB with clinically-relevant genotypes were recovered from 15 WWTPs (30%) of which 13 (50%) serviced large metropolitan areas and 2 (8.3%) represented small rural populations (P < 0.05). Recovery of CPB was lowest among WWTPs that utilized ultraviolet radiation for primary disinfection (12%), and higher (P = 0.11) for WWTPs that used chlorination (42%) or that did not utilize disinfection (50%). We did not detect a difference in CPB recovery by sampling site, although fewer CPB were detected in upstream (8%) compared to effluent (20%) and downstream (18%) samples. Our results indicate that WWTP effluent and nearby surface waters in the US are routinely contaminated with CPB with clinically important genotypes including those producing Klebsiella pneumoniae carbapenemase (KPC) and New Delhi metallo-beta-lactamase (NDM). This is a concern for both public health and animal agriculture because introduction of CPB into intensively managed livestock populations could lead to their amplification and foodborne dissemination.

LC-HRMS suspect screening to show spatial patterns of New Psychoactive Substances use in Australia

New Psychoactive Substances (NPS) are an ever-changing class of compounds designed to imitate the effects of current recreational drugs. Such a diverse market is difficult to assess by traditional means, while collected information can become obsolete before it is available. Wastewater-based epidemiology is one technique which can capture information on where and when NPS appear at the community level. The aim of this study was to identify NPS in wastewater samples using a suspect screening approach. Weekend samples were collected from 50 wastewater treatment plants from Australian capital cities and regional areas across all eight States and Territories and screened against a database containing almost 200 NPS. A total of 22 different NPS were found across all regional and metropolitan wastewater treatment plants. Results showed that the most detected compounds were of the cathinone class, with both Alpha-PVP and methcathinone found in every region. In addition, five different synthetic cannabinoids were detected, at least once in half of the regions analysed. Herein, we report the first comprehensive nationwide analysis of NPS and show the utility of liquid chromatography-high resolution mass spectrometry screening for delivering spatial information of the NPS being consumed in communities.

Evaluation of Heavy Metals and Associated Health Risks in a Metropolitan Wastewater Treatment Plant's Sludge for Its Land Application

ABSTRACTThe objectives of this study are to monitor the heavy metal concentrations in sludge samples collected from the Ankara Central Wastewater Treatment Plant (ACWWTP) in Turkey, check if these concentrations comply with the Turkish Regulation (Regulation Regarding the Use of Domestic and Urban Sludges on Soil), and evaluate possible health risks of heavy metals in sludge due to ingestion of sludge by a child. Monthly sludge samples were collected from the ACWWTP during 2012 and analyzed for seven heavy metals (Cd, Cr, Cu, Hg, Ni, Pb, and Zn). According to the results from the study, heavy metal concentrations showed no common seasonal trend. All heavy metal concentrations, except for one sample in which Zn was found to be at the limit value, are below the Turkish Regulation limits. In addition, health risks calculations for the “child ingesting biosolids” pathway, which is one of the most critical pathways identified by the U.S. Environmental Protection Agency (USEPA) for land application, were carried out. Among the seven heavy metals, Pb contributed the most to the cumulative non-cancer health risks throughout 2012. Nevertheless, the results showed that cumulative non-cancer health risks associated with this pathway are within the acceptable non-cancer health risk level suggested by USEPA.

Investigation of nonylphenol and nonylphenol ethoxylates in sewage sludge samples from a metropolitan wastewater treatment plant in Turkey

Nonylphenol ethoxylates (NPEOs) have drawn significant attention within the last decade for both scientific and legislative reasons. In Turkey, the Regulation Regarding the Use of Domestic and Urban Sludges on Land states a limit value for the sum of nonylphenol (NP), nonylphenol monoethoxylate (NP1EO) and nonylphenol diethoxylate (NP2EO) as NPE (NPE=NP+NP1EO+NP2EO). Unfortunately a standard method for the determination of these chemicals has not been yet set by the authorities and no data exists about the concentrations of NP and NPEOs in sewage sludge in Turkey. The aim of this study is to propose simple and easily applicable extraction and measurement techniques for 4-n-nonylphenol (4-n-NP), NP, NP1EO and NP2EO in sewage sludge samples and investigate the year round concentrations in a Metropolitan Wastewater Treatment Plant (WWTP) in Turkey.Different extraction techniques and GC/MS methods for sewage sludge were tested. The best extraction method for these compounds was found to be ultrasonication (5min) using acetone as the solvent with acceptable recovery of analytes suggested by USEPA and other studies. The optimized extraction method showed good repeatability with relative standard deviations (RSDs) less than 6%. The recovery of analytes were within acceptable limits suggested by USEPA and other studies. The limits of detection (LODs) were 6µgkg−1 for NP and NP1EO, 12µgkg−1 for NP2EO and 0.03µgkg−1 for 4-n-NP. The developed method was applied to sewage sludge samples obtained from the Central WWTP in Ankara, Turkey. The sum NPE (NP+NP1EO+NP2EO) was found to be in between 5.5µgkg−1 and 19.5µgkg−1, values which are in compliance with Turkish and European regulations.

Municipal gravity sewers: An unrecognised source of nitrous oxide

Nitrous oxide (N2O) is a primary ozone-depleting substance and powerful greenhouse gas. N2O emissions from secondary-level wastewater treatment processes are relatively well understood as a result of intensive international research effort in recent times, yet little information exists to date on the role of sewers in wastewater management chain N2O dynamics. Here we provide the first detailed assessment of N2O levels in the untreated influent (i.e. sewer network effluent) of three large Australian metropolitan wastewater treatment plants. Contrary to current international (IPCC) guidance, results show gravity sewers to be a likely source of N2O. Results from the monitoring program revealed hydraulic flow rate as a strong driver for N2O generation in gravity sewers, with microbial processes (nitrification and possibly denitrification) implicated as the main processes responsible for its production. Results were also used to develop a presumptive emission factor for N2O in the context of municipal gravity sewers. Considering the discrepancy with current IPCC Guidelines, further work is warranted to assess the scale and dynamics of N2O production in sewers elsewhere.

Validation of activated sludge plant performance for virus and protozoan reduction

Validation studies were undertaken at Adelaide metropolitan wastewater treatment plants to establish the actual log10 reduction values (LRVs) of pathogens (viruses and Cryptosporidium) across activated sludge plants (ASPs) as an alternative to accepting the default values attributed by the Department of Health and Ageing (DHA). Grab samples were collected across a 6-week period and assessed for pathogens (adenovirus and Cryptosporidium) and indicator microorganisms (sulphite-reducing clostridia and F-RNA bacteriophage). Through applying the validation process, the DHA has revised the default value for reduction of viruses with an increase from 0.5 log10 to 1 log10 while the value for protozoa remains at 0.5 log10 based on the combined data for a well-operated and maintained ASP. This provides the basis for considering further work at individual plants which may allow higher log credits to be obtained on a plant by plant basis.

Behavioral responses of adult male and female fathead minnows to a model estrogenic effluent and its effects on exposure regime and reproductive success

Laboratory studies of adult male fathead minnows have shown that when they are exposed to estrogens, they lose their ability to compete for access to females and sire young, suggesting that estrogenic effluents may reduce the genetic fitness of populations of wild fishes. However, it is unknown whether wild fish which are exposed to effluent actually compete with unexposed fishes, how long effects of estrogen exposure last, and whether females are affected by estrogens. This study addressed these issues using the fathead minnow (FHM) and effluent from the Metropolitan Wastewater Treatment Plant (MWTP) a well-studied source of environmental estrogens (EEs) in the Mississippi River. Maze tests found that adult FHMs are neither attracted nor repelled by MWTP effluent while previous studies have shown that minnows are attracted to the warmer waters which characterize effluents; it is realistic that previously unexposed fish enter MWTP effluent in the spring and then compete with exposed individuals. Competitive spawning experiments showed that male FHMs exposed to 44 ng E2/l (a high but realistic level) for three weeks failed to compete with unexposed males while males exposed to 4 ng E2/l outcompeted and sired more young than unexposed males ( p < 0.05). The effects of estrogen exposure disappeared within a week of moving fish into uncontaminated water. Female FHM reproductive output and behavior were unaffected by exposure to estrogen. Taken together, these experiments suggest that the behavior of wild fishes likely determines their exposure to EEs and that while the effects of this exposure are likely significant to populations of wild fish, they will be location specific because of factors which determine the duration and intensity of male exposure. We conclude that the role of fish behavior in endocrine disruption strongly warrants additional consideration.

Behavioral and genomic impacts of a wastewater effluent on the fathead minnow

Rivers containing effluents from water treatment plants are complex soups of compounds, ranging from pharmaceuticals to natural hormones. Male fathead minnows ( Pimephales promelas) were exposed for 3 weeks to effluent waters from the Metropolitan Wastewater Treatment Plant in St. Paul, MN. Fish were tested for their competitive nest holding behavior. Changes in vitellogenin were measured and these were correlated to changes in gene expression using a 22,000 gene microarray developed specifically for fathead minnows. Significant changes in gene expression were observed in both liver and testis, which correlate to phenotypic changes of vitellogenin induction and reduced competitive behavior. We also compared by real-time PCR the expression changes in key genes related to steroid biosynthesis and metabolism in fish exposed to the effluent as well as in fish exposed to a model estrogen and a model androgen. While the gene expression signature from effluent-exposed fish shared some elements with estrogen and androgen signatures, overall it was different, underscoring the complexity of compounds present in sewage and their different modes of action.

Total and methyl mercury transformations and mass loadings within a wastewater treatment plant and the impact of the effluent discharge to an alkaline hypereutrophic lake

Concerns over the fate and bioaccumulation of mercury (Hg) inputs to Onondaga Lake, a hypereutrophic lake in central New York, prompted an investigation into the concentrations and fluxes of Hg discharge from the Onondaga County Metropolitan Wastewater Treatment Plant (METRO WWTP). Discharge of methyl Hg (MeHg) is of concern because it is the form of Hg that readily bioaccumulates along the aquatic food chain. This study incorporated clean protocols for sampling and Hg analysis to evaluate: seasonal patterns in the concentrations of total Hg (THg) and MeHg in the WWTP unit processes; the production of MeHg within the unit processes of the WWTP; the overall fate of THg and MeHg within the WWTP; and the relative impact of the Hg discharged from the WWTP to Onondaga Lake. Concentrations of THg (range: 80–860 ng/L) and MeHg (0.7–17 ng/L) in raw sewage were highly variable, with higher concentrations observed in the summer months. The dynamics of THg though the WWTP were correlated with total suspended solids (TSS). As a result, the majority of the THg removal (55%) occurred during primary treatment. Overall, about 92% of the THg entering the plant was removed as sludge, with volatilization likely a minor component of the overall Hg budget. The transformation of MeHg through the plant differed from THg in that MeHg was not correlated with TSS, and displayed strong seasonal differences between winter (November to April) and summer (May–October) months. During the summer months, substantial net methylation occurred in the activated sludge secondary treatment, resulting in higher MeHg concentrations in secondary effluent. Net demethylation was the dominant mechanism during tertiary treatment, resulting in removal of substantial MeHg from the secondary effluent. The overall MeHg removal efficiency through the plant was about 70% with more efficient removal during summer months. Sediment trap collections made below the epilimnion of Onondaga Lake indicated average deposition rates of 12 μg/m 2-day for THg and 0.33 μg/m 2-day for MeHg. These deposition rates are more than an order of magnitude higher than the thermocline area normalized external loads from METRO effluent (0.85 μg/m 2-day for THg, 0.05 μg/m 2-day for MeHg). Our findings indicate that the impact of the discharge from METRO is relatively small, contributing about 10–15% of Hg to the total gross Hg input to the hypolimnion of the lake.

Modeling of Po River Water Quality in Torino (Italy)

The aim of this paper is to examine the Po river quality in a small stretch between two stations in Piedmont in the north of Italy. In this stretch a large pollution load is introduced and diluted in the fluent water of the river. The load has been quantified and about it we performed mass balances and modeling in order to understand the entity, the origin and the final fate of the immitted pollutants. In particular the objective of the work is to highlight the entity and the impact of Torino metropolitan area discharge on the quality of the same river. The obtained results show in particular, as well as the great impact of the Torino metropolitan area (the calculated pollution from Torino to the station downstream increases, for example for the COD of the 38%), the large contribute to the pollution from the Po river affluents (the pollution, for the COD, from Torino to the station downstream increases, considering the affluents too, of the 49%). The other fundamental point of investigation is the analysis of the impact produced by the Metropolitan Wastewater Treatment Plant (SMAT, Societa Metropolitana Acque Torino) on the quality of the water. The obtained results show that the SMAT Plant determines the environmental state of the Po river in the station downstream of the same treatment plant. At the end we have evaluated the general pollution state in order to highlight which interventions are necessary in order to respect what is prescribed from the Italian laws.

Performance Testing of a Biotrickling Filter/Chemical Scrubber Odor Control System at Western Australia's Largest WTTP

In 2006 the Water Corporation of Western Australia formed the W2W Alliance (W2WA) to deliver a five-year $352 million program of upgrades to the State’s three largest metropolitan wastewater treatment plants (WWTPs). At the Woodman Point WWTP, W2WA was tasked with installing best practice odor control to achieve a 50 percent reduction in odor emmissions. The Stage 1 odor control improvements involve new covers of the grit tanks, sealing existing covers at the primary treatment area, and new covers and extraction systems for sludge treatment areas and SBR anoxic zones. Biotrickling filters followed by chemical scrubbers offered the best solution for treating the extracted air. The Stage 1 commissioning in 2009 was very successful with no odor incidents during startup of the facilities. The biotrickling filters acclimated faster than expected and reduced inlet hydrogen sulfide (H2S) as high as 80 parts per million (ppm) to less than 0.5ppm. Biotrickling filter performance testing showed outlet odor ranging from 1,020 to 3,160 Odor Units (OU), which met the requirment of 5,000 OU. The odor reduction goal of greater than 95 percent was also achieved. Chemical scrubber performance testing showed inlet H2S as high as 37ppm reduced to less than 0.05ppm, which met the 0.1ppm requirement. Odor removal was relatively good, but some stack outlet samples were above the 1,000OU goal. When the combined system is tested, it is expected that the outlet odor goal can be met when the chemical scrubber is receiving lower inlet loads.

Historical trends affecting accumulation of sediment and phosphorus in Lake Pepin, upper Mississippi River, USA

This study was conducted to collect historical land use information that would help explain the historical patterns in accumulation of sediment and phosphorus in Lake Pepin documented by Engstrom et al. (J Paleolimnol, this issue). A wide range of historical factors including cropping systems, phosphorus applications from fertilizer and manure, human and animal populations, river flows and phosphorus discharges from waste water treatment plants were studied using statistical methods. Results showed that sediment losses from the Minnesota River basin are significantly correlated with historical increases in river flows, row crop production acreage and basin population. Total phosphorus accumulations in the sediments of Lake Pepin are significantly correlated with increased phosphorus discharges from metropolitan area wastewater treatment plants, and increases in row crop acreage and river flows. Total phosphorus inflows to Lake Pepin are significantly correlated with increases in river flows, row crop acreage and phosphorus fertilizer applied to agricultural lands.

Investigation of potato starch and sonicated RAS as alternative carbon sources for biological nitrogen removal

High nitrogen discharge from wastewater is a major concern for the South Australian Government, primarily due to the negative impacts on the marine environment. Therefore, under the South Australian Environmental Improvement Program (SA EIP), all metropolitan wastewater treatment plants have been reconfigured to achieve enhanced nitrogen removal. Secondary treatment (denitrification processes) at the metropolitan wastewater treatment plants must be optimized to meet the discharge guideline of 10mg/L total nitrogen. However, secondary treatment at some plants is carbon limited (low C/N ratio), and external carbon supplementation is required to meet the discharge guideline. Molasses provides the current external carbon source at two plants. It is relatively inexpensive but other carbon sources, particularly industrial waste streams, may be more attractive. Potato starch and sonicated return activated sludge (RAS) are considered. Ongoing work will evaluate the benefit/cost of these alternative carbon feedstocks. Soluble carbon release (SCOD) from the two sources is quantified and preliminary results are presented. Initial results suggest that sonicated RAS may be an attractive substitute for the molasses.