Browsing by Subject "wastewater"

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Advanced treatment technologies that remove solids from municipal wastewater consistently meet mercury effluent limits.
(2022-06) Hogan, Kelsey
Since many other sources of mercury (Hg) are difficult to control, the removal of Hg from wastewater is an essential component of maintaining low Hg levels in ecosystems. Numerous studies have investigated solid-liquid interactions of Hg at ng/L levels in natural systems, but few studies have translated insights to highly-engineered, organic-rich systems such as municipal wastewater treatment plants. There is a lack of guidance for design engineers concerned with meeting exceptionally low-level Hg limits, particularly the 1.8 ng/L limit applicable to the Laurentian Great Lakes. A historic Minnesota Pollution Control Agency dataset from over 150 municipal wastewater treatment plants (MWWTP) was analyzed and categorized into technology types. Starting with secondary technology types and continuing to tertiary technology types, Hg concentrations from MWWTP in each technology type were analyzed to indicate if there are technologies that reliably reduce HgT in the effluent to below 1.8 ng/L. Additionally, correlations between total suspended solids (TSS) and HgT (total Hg) were evaluated. Certain technology types were better at removing HgT than others. Secondary technologies including conventional activated sludge, MBRs, and polishing ponds as well as tertiary technologies including fine dual media filters, rotating cloth membrane, and deep bed mono-media filters all consistently meet low-level HgT discharge limits. Effluent HgT measurements were correlated with TSS for several secondary technologies with a hydraulic residence time similar to conventional activated sludge, while technologies with very short (attached growth) or very long (ponds) showed little relation between TSS and HgT in effluent water. Nonparametric statistics were used to compare the effluent HgT among technologies and estimate the reliability of meeting mercury limits. The results of this study could help MWWTP determine appropriate technologies to install to meet regional or state mercury discharge limits.
Algae-Assisted Nutrient Removal From Municipal Wastewater
(2020-04) Sorenson, Carlise
Wastewater treatment continues to draw attention as a potential source of eutrophication. As stricter regulations are implemented research and development must address the need for improved treatment designs. This study focused on the treatment efficiency of the treatment systems as well as the cost and energy demand or operation. In the following research a co-culture of algae and activated sludge were investigated for their ability to provide improved nutrient removal to wastewater treatment systems. This culture was tested in a sequencing batch reactor and a plug flow reactor to model large scale municipal wastewater treatment and onsite household septic tanks respectively. This culture provided significant treatment of nutrients in both studies. Further experimentation and optimization of these treatment designs is needed to address the cost of operation.
Anaerobic Co-Digestion of Municipal Wastewater Sludge and High Strength Waste: An Evaluation of Waste Degradation Potentials
(2015-12) Prok, Amy
Research has demonstrated the abundant treatment and economic opportunities presented by co-digestion of high strength wastewater, but these wastes also have the potential to cause digester failure. Indeed, based on what is known about the disruption of digesters, if a municipality is considering co-digestion, it needs to know the characteristics of high strength wastewaters that have a predictable potential for disruption. The Metropolitan Council-Environmental Services (MCES) is one such municipality interested in pursuing co-digestion. MCES is interested in expanding current digester use to include co-digestion of high strength waste streams to reduce their energy and sludge disposal costs. The objective of this research was to develop a protocol for MCES to be used in evaluating the feasibility of co-digesting municipal wastewater sludge with other high strength wastes. The protocol involves anaerobic biochemical methane potential (BMP) assays inoculated by source anaerobic digesters and amended with PBS, sludge (TPS/TWAS mixture), waste, or waste combined with sludge. Co-digestion experiments examined well-characterized synthetic wastes (starch, gelatin, tween 80, and cysteine) and wastes of interest to MCES with unknown impacts (dimethylformamide, dairy processing waste, propylene glycol, ethylene glycol, thickened primary sludge, thickened waste activated sludge, and scum collected from the primary clarifier at an MCES wastewater treatment facility). These wastes were characterized as degradable, non-degradable, toxic or degradable after an adaptation period. Gelatin, tween 80, dairy processing waste, ethylene glycol, and propylene glycol were degradable, while dimethylformamide was non-degradable. Cysteine, a sulfur-rich waste, was found to be toxic at concentrations greater than 200 mg/L. Scum, ethylene glycol, and propylene glycol required an adaptation period before being degraded. Additionally, the microbial analysis via qPCR indicated that the abundance of Bacteria and methanogens in the co-digestion experiments were not statistically different from the sludge-only experiments, even when different types of wastes were tested (i.e., degradable, non-degradable, toxic, etc.). The developed method and subsequent guidelines will be useful for MCES and other wastewater treatment facilities when making informed decisions about whether or not to accept potential high strength wastes for co-digestion with sludge.
Characterization of Antibiotic Resistant Genes in Two Unique City Sewer Systems
(2020-12) Keppers, Adelle
Sewer systems are known as point sources for the release of antibiotic resistance into the environment. Antibiotic resistance genes (ARGs) provide bacteria the ability to fight antibiotics and are viewed as emerging contaminants in environmental waterways. To minimize the spread of ARGs to the environment, this study assessed the prevalence of ARGs in upstream sewer systems that feed into wastewater treatment plants (WWTPs) so that source control strategies can be developed to mitigate the spread of antibiotic resistance. Wastewaters were examined from two unique city sewer systems containing three source types: hospital, residential, and industrial. Twenty-nine ARGs, 3 integron-intergrases, and 4 metal resistance genes were quantified using conventional and microfluidic polymerase chain reactions. Bacterial community compositions were characterized using high-throughput 16S rRNA amplicon sequencing. We found the levels of ARGs and bacterial community compositions to be dependent on the source of wastewater, the city, and the season. The abundance of ARGs in hospital wastewater were relatively constant and associated with clinically relevant antibiotics. ARG abundance in residential wastewater showed seasonal variations with high levels in winter associated with outpatient antibiotics. High levels of integron-integrase genes, a proxy for horizontal gene transfer and anthropogenic impacts, were also observed in residential wastewaters. Based on these findings we suggest satellite treatment of ARGs at hospital and residential sources to reduce their loading to WWTPs and their inevitable release to the environment.
Data for Quaternary ammonium compounds (QACs) in wastewater influent and effluent collected throughout the COVID-19 pandemic
(2024-01-08) Mahony, Anna K; McNamara, Patrick J; Arnold, William A; mahon445@umn.edu; Mahony, Anna K; University of Minnesota Environmental Engineering Arnold Lab
The dataset contains the concentrations of quaternary ammonium compounds detected in influent and effluent wastewater, as well as absolute recoveries of QACs spiked into influents and effluents, and absolute recoveries of isotopically labeled surrogate standards, spiked into all samples. After extraction from wastewater, samples are analyzed on a liquid chromatography tandem mass spectrometry (LC-MS/MS), specifically a triple quadrupole mass spec. Raw data from this instrument is provided as well, in the "Raw QQQ data" tab.
High-rate Resource Recovery from Wastewater with Encapsulated Biomass
(2020-01) ZHU, KUANG
This dissertation describes the recovery of a high-value resource during anaerobic wastewater treatment using encapsulated biomass with specialized functions. The encapsulant was formed into a bead and consisted of a customizable alginate gel matrix. Biomass was encapsulated within the bead, enabling the retention of high concentrations of specific communities of biomass in reactors even when operating reactors with a low hydraulic retention time (HRT). The effects of encapsulant customization, including that of cross-linking agents (Ca2+, Sr2+, and Ba2+) and a composite coating on the beads (alternating layers of polyethylenimine (PEI) and silica hydrogel), on the biomass retention ability and mass transport performance was quantified. The diffusion of the organic carbon in brewery wastewater through the alginate encapsulation matrix was not affected by the cross-linking agent and was comparable to that of glucose in water. As a result, the biomass encapsulated in uncoated beads was not substrate limited and high rates of hydrogen production from brewery wastewater were observed, even at an HRT of 45 min. Suspended biomass controls were not able to maintain hydrogen production at this low HRT because the biomass was washed out. Although the coating reduced the biomass escape rate from the encapsulant, it created a mass transport barrier to substrates, reducing both the diffusivity and the partition coefficient of organic carbon. This resulted in lower hydrogen production rates from brewery wastewater compared to the uncoated encapsulation system. A diffusion-reaction model describing the encapsulation system was also developed to predict, and therefore optimize, the hydrogen production rate under various encapsulant customization schemes and operating conditions. Experimental data collected from flow-through reactors with encapsulated biomass fed brewery wastewater were used to calibrate and validate the model. The model was capable of successfully predicting the general hydrogen production trends as a function of HRT, bead size, and wastewater strength. A sensitivity test conducted with the model revealed that the hydrogen production process with encapsulated biomass from brewery wastewater was growth limited and was sensitive to the substrate partition coefficient into the encapsulation matrix, initial encapsulated biomass concentration, and the total volume of beads in the reactor. The effect of encapsulation on hydrogen and methane production when encapsulated biomass was incubated in the presence of several known inhibitors was also investigated to determine whether and how the encapsulating matrix mitigated or exacerbated inhibition by different types of chemicals. The charge of the inhibitors appeared to play a dominant role in how they partitioned into the encapsulation matrix. Dichromate (negatively charged) appeared to be repelled by the alginate matrix while ammonium (positively charged) concentrated into the matrix. Chloroform (uncharged) was unaffected by the matrix and was neither repelled by nor concentrated into it. This was thought to be a result of electrostatic interactions with alginate. As a result, the matrix mitigated dichromate inhibition, increased ammonium inhibition, and had no impact on chloroform inhibition of the encapsulated biomass. Copper, on the other hand, chelated with alginate and the PEI coating, even though it partitioned into the matrix, appeared to be non-bioavailable, completely eliminating inhibition of the hydrogen-producing biomass. These results were also confirmed with an encapsulated methane-producing anaerobic community, demonstrating that the ability of the encapsulant to mitigate or exacerbate inhibition was applicable beyond hydrogen-producing biomass. Finally, a pilot-scale system was built and deployed at a brewery. The system consisted of a single hydrogen-producing reactor containing encapsulated biomass in series with parallel methane-producing reactors, one containing encapsulated biomass and a second containing suspended biomass in a membrane bioreactor configuration. Performance during intermittent operation and perturbations was monitored along with shifts in the microbial community in the two parallel methane-producing reactors. A more rapid recovery after perturbation was observed in the membrane bioreactor. In addition, its microbial community was similar to that sampled from the bulk solution of the reactor containing encapsulated biomass. The encapsulated biomass had a distinct microbial community structure, even though both reactors were inoculated with the same culture. This demonstrated that the community in the membrane bioreactor was able to adapt and change with time, apparently enabling faster recovery from perturbations. This appears to be a potential problem with encapsulated biomass, particularly if highly variable wastewater is being fed to the reactors or the system is expected to experience upsets and operational perturbations. This multi-faceted investigation of a customizable alginate encapsulation system for high-rate recovery of resources during anaerobic wastewater treatment provided insights regarding how to design the system for good performance. It also provided further information regarding potential problems that could be encountered when using encapsulated biomass for treatment. Overall this system offers the potential for low-maintenance decentralized anaerobic wastewater treatment. More work is needed, however, to facilitate robust and reliable treatment and to provide guidance for system optimization and further life cycle assessment.
Long Lake Wastewater Feasibility Study.
(1999) Bankston, Jamie
Maximum Application Rates for Land Treatment of Septage
(Water Resources Research Center, University of Minnesota, 1983-05) Anderson, James L.; Clanton, C.J.; Hansel, M.J.; Machmeier, R.E.
During 1980, septage was applied in rates of 1120 and 1500 kg of nitrogen per hectare to three different soil textures in an attempt to determine maximum loading rates. These rates resulted in increased concentrations of nitrates in the soil water for a Hubbard loamy Sanci, Waukegan silt loam and Lester clay loam, indicating that the application rates exceeded the maximum rate that the soils could treat. The first year's results indicate that soil type, application rates and soil depth resulted in no significant difference in total Kjeldahl nitrogen, ammonia, fecal streptococcus and fecal coliforms in the soil water samples. Nitrate concentrations, however, were significantly different between the soils, application rates and soil depths. For the Hubbard loamy sand, rainfall had a larger effect on nitrate concentrations and movement within the soil profile than for the Waukegan silt loam or Lester clay 1oam. 0n the Waukegan silt loam and Lester clay loam there was relatively little change in the nitrate concentration in the soil profile during the period when septage was applied twice a week. After the design loading had been applied to the soil and no further applications made, a sharp increase in nitrate concentrations was observed in the soil profile. This probably resulted from changing the anaerobic surface layer to an aerobic condition resulting in nitrification and subsequent movement of nitrates through the profile following a rainfall event. With no additional septage application, the second year's data indicate a significant difference in nitrate-N between soils, application rates, and depths. Generally, the nitrate concentrations in the Hubbard loamy sand and Waukegan silt loam were less than the first year, but the concentrations in the Lester clay loam were higher than the first year. This indicates that nitrification and nitrate movement in the Lester clay loam are slower than the other two soils. Application resulted in a significant increase in the concentration of soil water calcium, magnesium, sodium and potassium during the first year of the study. However, there was no increase in the phosphorus content of the soil water.
A modular technology for fermentative hydrogen production and capture from wastewater
(2014-11) Sigtermans, Louis
Despite the inherent chemical energy in wastewater, current wastewater treatment practices expend a considerable amount of energy to aerobically remove organic pollutants. Anaerobic fermentation of these dissolved organics to produce hydrogen could instead provide a positive energy output while delivering the ancillary benefit of lessening aeration demands for downstream treatment processes. A scalable and modular technology, based on the membrane-encapsulation of hydrogen-producing mixed consortia onto hollow fiber membranes for efficient hydrogen collection, was developed to produce and capture hydrogen from dissolved phase organics in wastewater. The membranes were tested in a continuously stirred tank reactor (CSTR) and monitored for hydrogen production and capture. The results showed that two different membrane polymer chemistries were successful in producing and capturing hydrogen from high-strength synthetic wastewater, with maximum captured yields of 25-50 mL/g hexose. Low available carbohydrate content, pH conditions, and leakage of microorganisms into and out of the membranes may have contributed to the failure of hydrogen production in trials using municipal wastewater. Batch tests of dairy manufacturing waste demonstrated the potential for future application of this technology for producing hydrogen from a real industrial wastewater.
Regional Sewer System Rate Structure Study.
(1992) Luce, Thomas F.; Lukermann, Barbara L.; Mohring, Herbert
Seasonal Variations In The Activated Sludge Microbiome With Respect To Seasonal Nitrification Failure
(2020-07) Johnston, Juliet
Activated sludge consists of a diverse microbial community that is used by wastewater engineers to metabolize excessive nutrients in domestic wastewater so that these excessive nutrients do not impact downstream waters. While most biological contaminant removal processes, such as carbon (measured as Biological Oxygen Demand) and phosphorous removal are performed consistently year-round, nitrification performance significantly declines in cold temperatures. The seasonal decline in nitrification performance is known as seasonal nitrification failure. To understand seasonal nitrification failure, this thesis analyzed triplicate, full-scale, sequencing batch reactors throughout several years to investigate seasonal variations in the activated sludge microbiome with respect to community composition (16S rRNA gene), the metabolically active composition (16S rRNA transcript), and expression of amoA (ammonia monooxygenase) which is a key-nitrification functional gene. There were 114 OTUs (operational taxonomic units), which were consistently present in all three reactors, every week, for an entire year and together comprise 74.3% - 84.0% of the entire community. The changes in abundances of these OTUs and other seasonally present OTUs make each season’s community significantly distinct from each other. The community composition was also significantly distinct from the protein-synthesis composition throughout the entire year. While the entire activated sludge community and protein-synthesis compositions fluctuated, the ammonia-oxidizing community was at a constant abundance throughout the year based on tracking known ammonia oxidizers and the amoA functional gene despite seasonal nitrification failure. While the amoA transcripts declined with the seasonally cold temperatures, which explain the seasonal nitrification failure’s decline in activity, the known-ammonia oxidizer protein-synthesis potential measured by Nitrosomonas sp. 16S rRNA transcripts did not significantly decline with temperature. This suggests there are other metabolic activities performed by the known ammonia oxidizing community to maintain stable community abundance and protein synthesis potential when ammonia oxidization is no longer the most thermodynamically favorable metabolism. This result changes the narrative that seasonal nitrification failure occurs due to declining abundances of ammonia oxidizing organisms in cold temperatures, and instead provides insight as to how amoA expression seasonally changes with the complex and seasonally dynamic microbial ecology of the activated sludge community. Additionally, this research provides the most comprehensive baseline of the activated sludge communities seasonal composition, protein-synthesis potential and amoA expression to date. Future researchers can use these results to investigate specific highlighted seasonally variant OTUs which may influent the activated sludge microbiome, as well as explore the additional roles known ammonia oxidizers play in this complex microbial system.
Sedimentary Record of Antibiotic Accumulation in Minnesota Lakes
(2018-01-29) Arnold, William A; Kerrigan, Jill F; Sandberg, Kyle; Engstrom, Daniel R; LaPara, Tim; arnol032@umn.edu; Arnold, William; Arnold, William
The widespread detection of antibiotics in the environment is concerning because antibiotics are designed to be effective at small doses. The objective of this work was to quantify the accumulation rates of antibiotics used by humans and animals, spanning several major antibiotic classes (sulfonamides, tetracyclines, fluoroquinolones, and macrolides), in Minnesota lake-sediment cores. Our goal was to determine temporal trends, the major anthropogenic source to these lacustrine systems, and the importance of natural production. A historical record of usage trends for ten human and/or animal-use antibiotics (four sulfonamides, three fluoroquinolones, one macrolide, trimethoprim, and lincomycin) was faithfully captured in the sediment cores. Nine other antibiotics were not detected. Ofloxacin, trimethoprim, sulfapyridine, and sulfamethazine were detected in all of the anthropogenically-impacted studied lakes. Maximum sediment fluxes reached 20.5 ng cm−2 yr−1 (concentration 66.1 ng/g) for ofloxacin, 1.2 ng cm−2 yr−1 (1.2 ng/g) for trimethoprim, 3.3 ng cm−2 yr−1 (11.3 ng/g) for sulfapyridine, and 1.0 ng cm−2 yr−1 (1.6 ng/g) for sulfamethazine, respectively. Natural production of lincomycin may have occurred in one lake at fluxes ranging from 0.4 to 1.8 ng cm−2 yr−1 (0.1 to 5.8 ng/g).Wastewater effluent appears to be the primary source of antibiotics in the studied lakes, with lesser inputs from agricultural activities.
Van's Island: Wastewater Treatment and Next Steps
(2003) Steiner, Benjamin

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