Journal of Environmental Engineering

Anaerobic digestion (AD) of synthetic and real dairy wastewater was the focus of the study for parametric estimation of kinetic models with examining biochemical methane potential (BMP), treatment efficiency, and energy effectiveness of the process. The effect of substrate-to-inoculum ratio ($S/I$) on batch reactor performance was investigated under mesophilic ($35°\mathrm{C}\pm 2°\mathrm{C}$) conditions for 30 days. Based on the volatile solid (VS) content, three different $S/I$ ratios were considered: $1:1$ (Treatment A), $1:3$ (Treatment B), and $1:6$ (Treatment C). Organic matter removal in VS units was as high as 56%. Almost 90% of the biogas was produced during the first 14 days of digestion, with a biogas yield of $337\pm 23$, $305\pm 48$, and $356\pm 37\mathrm{mL}/\mathrm{g}$ VS for Treatments A, B, and C, respectively. Methane content increased with increasing inoculum amounts in the medium. The experimental cumulative methane yield from both synthetic and real dairy wastewater was contoured for parametric estimation in four different kinetic models, namely first-order (FO), modified Gompertz equation (GE), modified logistic (LM), and modified transference (TM) models. The modified TM model was the best fit for overall treatment, with predicted methane production potential of 279.8 and $235.9\mathrm{mL}/\mathrm{g}$ VS compared with the experimental value of 272 and $229\mathrm{mL}/\mathrm{g}$ VS in treatment C for synthetic and real dairy wastewater, respectively. Preliminary studies showed the potential of energy generation, which may supplement 32% of the overall energy use. These results demonstrate the importance of understanding the effect of the $S/I$ ratio involved in AD to treat synthetic and real dairy wastewater.

Applying mechanistic water quality analysis models that are proficient at simulating the dynamics of heterotrophic bacteria within distribution pipes is a pragmatic approach to maintaining biological stability during drinking water distribution systems (DWDS) operation. Accurate interpretation of hydrodynamics and the uncertainties associated with the multifaceted exchanges within the distribution pipes is crucial to the reliability of these models’ predictions. However, knowledge about most exchanges within DWDS is still inadequate. Therefore, state-of-the-art mechanistic models exist merely as theoretical frameworks to understand the causes and effects of microbiological quality fluctuations in DWDS, and they lack general applicability. Advancing the applicability and reliability of the mechanistic models necessitates adequate consideration of epistemic and aleatory uncertainties. This study developed mechanistic models to realize the degree of complexity that needs to be integrated into the modeling framework to accurately describe the water quality dynamics in a real-world DWDS. Under the test conditions considered, the simplest single-phase models that ignore the complex exchanges associated with the pipe biofilm layers were found to make similar microbiological quality predictions as the relatively complicated two-phase models. The results indicate that the knowledge uncertainty associated with mechanisms concerning heterotrophic bacterial regrowth in the bulk phase and biofilm detachment in the wall phase is critical in controlling the reliability of the mechanistic water quality models.

Proper treatment of dye wastewater containing significant concentrations of organic matter is imperative for the abatement of water pollution. Unfortunately, most studies on the treatment of dye wastewater employ synthetic wastewaters that hardly match the characteristics of real wastewater. In the present study, real wastewater generated from the manufacturing of Solvent Black 46 (SB46) dye was treated in an internal circulation reactor, modified with a bed of sponge cubes. The reactor was operated in different phases to investigate the impact of parameters such as feed chemical oxygen demand (COD), organic loading rate (OLR), and hydraulic retention time (HRT) on COD removal and methane generation. At a feed COD concentration of $\mathrm{10,000}\mathrm{mg}/\mathrm{L}$ and an OLR of up to $3\mathrm{Kg}\mathrm{COD}/{\mathrm{m}}^3/\mathrm{day}$, 82% COD was removed with methane generation ranging from 0.28 to $0.31\mathrm{L}/\mathrm{g}\text{-}\mathrm{COD}$ removed. COD removal and methane generation increased with an increase in upflow velocity. The rate of substrate (COD) removal correlated well with the organic loading rate using the modified Stover–Kincannon model with a correlation factor (${\mathrm{R}}^2$) of 0.9974. LC-MS analysis of treated wastewater revealed that one of the constituents of SB46, namely Metanil yellow, was decomposed by azo bond cleavage, producing corresponding aromatic amines. Overall, this study provides evidence of the successful anaerobic treatment of real industrial wastewater and its potential contribution to achieving UN Sustainable Development Goals 6 (Clean Water and Sanitation) and 7 (Affordable and Clean Energy). Importantly, the process parameters developed in this study have been utilized by the industry to install two full-scale anaerobic reactors to treat SB46 wastewater which has led them to double the SB46 production while conforming to the prescribed environmental discharge norms.

The massive generation of pig manure significantly contributes to the emission of greenhouse gases; in addition, its poor disposal represents a serious risk to human and animal health. In recent years, the microbial fermentation process has become relevant because it is considered a circular bioeconomy strategy, guaranteeing the recovery of agro-industrial waste and waste management. In this work, the production of lactic acid and biomass was evaluated from an anaerobic bioconversion process of swine residues in the presence of L. acidophilus. A 5 L capacity reactor was used, and different stirring speeds were evaluated (100, 150, and 200 rpm). It was concluded that the highest production of lactic acid and biomass was 30.15 and $111.52\mathrm{g}/\mathrm{L}$, respectively, which were reached during the experiments carried out at 100 rpm. The biomass was analyzed to determine the content of carbohydrates, proteins, and cell count, which were $0\mathrm{g}/\mathrm{L}$, 17.16%, and $3.45\times {10}^7\mathrm{cfu}/\mathrm{g}$, respectively. Finally, the fuzzy logic technique was applied, and response surface graphs were generated to determine the variables with the greatest impact on lactic acid and biomass generation.

Climate change and urbanization are resulting in increased runoff for stormwater sewers to handle. This work uses hydraulic modeling and typical US prices to quantify the cost increase due to the larger pumps and pipes that will be needed for various amounts of discharge increase. Analysis was performed on a single sewer pipe and pump but also on a hypothetical system of varying sizes, incorporating cost for pipes pumps, and electricity usage. It was found that gravity-flow systems will cost up to nine times more than the current design amount. Cost increases can be estimated by a linear function with slope ranging from 0.025 to 0.019. The cost can increase by a factor of 0.24 for a 30-pipe system at a slope of 0.0001 and as little as 0.03 for a single pipe system at a slope of 0.0019. For a force main, the cost increase ratio is a function of the discharge ratio to the 0.5 power. For corrugated pipes, the cost ratio varied from 31% to 39% from that of concrete pipe and from 20% to 22% for a PVC pipe, making additional funds necessary. This has implications for total maximum daily load (TMDL) because more stormwater, especially of pollutant concentration greater than the TMDL concentration, will be entering surface water bodies subject to TMDL regulations.

Poisoning of soil and groundwater resources is among the current major environmental issues worldwide. One effective way to stop the spread of pollutants and improve soil’s capacity for adsorption is to use natural and inexpensive adsorbents. In this respect, the soil environment can be improved by the addition of zeolite and rice husk ash (RHA). This study examined the behavior of a sand mixture with 20% kaolinite or 20% bentonite in both uncontaminated and contaminated [with ${\mathrm{Pb}(\mathrm{NO}}_3{)}_2$] states. Two classes of clay minerals were considered: kaolinite and bentonite. The impact of the adsorbent on the strength performance of the contaminated soil was examined by removing 10% of the clay particles and replacing them with zeolite or RHA adsorbents. Triaxial dynamic and bender element tests were carried out to explore the dynamic behavior of contaminated soils and the liquefaction resistance of the samples polluted with ${\mathrm{Pb}(\mathrm{NO}}_3{)}_2$, respectively. The results show that by reducing the heavy metals concentration ${\mathrm{Pb}(\mathrm{NO}}_3{)}_2$, the ultimate strength of sand mix with 20% bentonite increased by 40%–50%. In addition, the ultimate strength increased in polluted and noncontaminated situations by adding zeolite or RHA to the soil. The results of triaxial dynamic tests demonstrated that liquefaction resistance was reduced by increasing the contamination concentrations in both the mixes without and with adsorbent. Furthermore, the initial/maximum shear modulus ($G_0/G_{\max }$) decreased as the adsorbent content increased in both contaminated and noncontaminated states.

Nanofiltration concentrated leachate (NFCL) is a high-concentration organic wastewater produced from landfill leachate during the process of membrane advanced treatment, which is more difficult to treat than landfill leachate. In this study, the effect and cost of treating NFCL by flocculation combined with a multistage ozone/bioreactor process based on a field scale are discussed. The results show that the process has a good effect on the removal of organic matter and nitrogen pollutants in NFCL, with removal efficiencies of chemical oxygen demand, ammonia nitrogen, nitrate, and total nitrogen being 96.6%, 90.1%, 38.2%, and 75.8%, respectively. The effluent can meet the discharge standard of China’s standard with a direct operating cost of approximately USD $18.48–20.82/{\mathrm{m}}^3$. This study proved the effectiveness, structural rationality, and economic benefit of the process in a practical engineering application, and provided a certain theoretical basis and engineering reference for the wide application of the process in the treatment of leachate membrane concentrate.

Abstract

Wastewater treatment facilities and sewage collection systems provide essential services to society that can be negatively affected by increased infiltration and inflow (I&I). Ten case studies examined the construction and operation phases of wastewater infrastructure serving small communities (<4,000 people); the case studies were used to analyze the environmental, economic, and additional impacts and benefits from I&I mitigation using life-cycle assessment (LCA), cost data, and anecdotal information. Consistent with existing literature, I&I mitigation projects completed where initial flow was greater than 454 L (120 gal.) per capita per day were economically and environmentally advantageous. It was found that mitigating I&I is often one of the most significant practices existing facilities can implement to reduce environmental impacts. Overall environmental impacts for mechanical wastewater resource recovery facilities (WRRFs) were reduced in six of seven case studies. Conversely, overall environmental impacts from lagoons were reduced for one of three case studies. Environmental impact reductions were typically tied to reduced operational energy and/or water pollutant emissions. Generally, I&I mitigation costs are small compared to estimated original facility costs. Additional impacts and benefits include improved wet weather resilience and reduced maintenance, which were commonly cited by staff as highly important.

Practical Applications

Consistent with existing literature, I&I mitigation projects completed where initial flow was greater than 454 L (120 gal.) per capita per day were economically and environmentally advantageous, especially for mechanical plants. Lagoon systems in this study exhibited more complex results after I&I mitigation projects, which were driven by characteristics such as limited electricity usage, minimum water depth requirements, and discharge elimination. Reduced operational energy usage and improved treatment were major benefits of I&I mitigation projects and realized by a majority of case studies surveyed. Avoided future material usage related to avoided construction or equipment was also shown to be beneficial. Some case studies completely offset material usage for mitigation projects by avoiding other improvements that would have otherwise been required. Avoided construction for plant expansion is an additional major economic and environmental impact benefit of I&I mitigation but is often difficult to quantify. Additional major benefits of I&I mitigation commonly cited by staff include improved wet weather resilience and reduced maintenance.

Wastewater disinfection is a key treatment for the protection of the environment and public health from pathogenic infections. Peracetic acid (PAA) is an organic peroxyacid with a high oxidation potential that can be an alternative to conventional disinfectants. The aim of this pilot-scale study was to assess six disinfection conditions using PAA as a disinfectant agent of wastewater. To this end, a 6-month study was performed, and six disinfection conditions were studied: $15\mathrm{mg}/\mathrm{L}$ of PAA with 5, 10, and 15 min of contact time; $10\mathrm{mg}/\mathrm{L}$ of PAA with 10 and 15 min of contact time; and $5\mathrm{mg}/\mathrm{L}$ of PAA with 10 min of contact time. After the disinfection, an increase in the 5-day biochemical oxygen demand (${\mathrm{BOD}}_5$) and the chemical oxygen demand (COD) was observed; however, this was not proportional to the PAA dose because the higher doses tested did not result in a higher increment. In addition, PAA resulted in a slight decrease in pH. Nevertheless, the PAA impact on pH was not dependent on the PAA dose or the contact time. The PAA disinfection performance showed that doses of 10 and $15\mathrm{mg}/\mathrm{L}$ achieved Escherichia coli log reduction higher than 2 logs, and even higher than 3 logs when $15\mathrm{mg}/\mathrm{L}$ were tested with 10 and 15 min of contact time. The results showed also that the contact time was not a limiting factor for the PAA performance, at least for the contact times used in this study. This pilot-scale study proved that PAA can be an alternative disinfectant for wastewater.

Wastewater surveillance has been widely implemented to monitor COVID-19 incidences in communities worldwide. One notable application of wastewater surveillance is for providing early warnings of disease outbreaks. Many studies have reported time lags between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) wastewater concentrations and confirmed clinical COVID-19 cases. To our best knowledge, only a few studies to date have explored time lags between SARS-CoV-2 wastewater concentrations and other clinical metrics. In this study, we investigated time lags between SARS-CoV-2 wastewater concentrations and three COVID-19 clinical metrics: confirmed clinical cases, hospitalizations, and intensive care unit (ICU) admissions, in the Tricounty Detroit Area, Michigan, US. The COVID-19 clinical metrics were dated between September 1, 2020, and October 31, 2022, and were collected from public data sources. SARS-CoV-2 N1 and N2 gene concentrations between September 1, 2020, and May 31, 2022, were generated using two sampling and concentration methods: virus adsorption-elution (VIRADEL) and polyethylene glycol precipitation (PEG). The data were collected from our recently published study. Time-lagged cross correlation was implemented to estimate time lags between gene concentrations and the three clinical metrics. Original gene concentrations were normalized by wastewater flow parameters through nine approaches to estimate the impact of wastewater flow on time lags. Vector autoregression models were established to analyze the relationship between gene concentrations and clinical metrics. The results indicate that VIRADEL gene concentrations in wastewater preceded all clinical metrics prior to the COVID-19 Omicron surge, for instance, 32, 47, and 51 days preceding confirmed cases, hospitalizations, and ICU admissions, respectively (gene concentrations unit: $\mathrm{gc}/\mathrm{day}$). When translated to a public health context, these time lags become critical lead times for officials to prepare and react. During the Omicron surge, there were significant reductions in time lags, with VIRADEL measurements trailing total ICU admissions. PEG measurements lagged behind the three clinical metrics and did not provide early warnings of disease surges.