Estimation of greenhouse gases from sewage from on-site sewage management system

The rapid growth in population has rendered the centralized sewerage systems a non-realistic option in sparsely populated areas. Consequently, an on-site wastewater treatment system (OWTS) is a viable alternative and cost-effective solution of sewerage system. Septic tanks with soil absorption systems are a simple mean of onsite treatment of the domestic wastewater. However septic tanks have low treatment efficiency along with several technical and constructional drawbacks. In order to improve the performance efficiency of conventional septic tank, a two-stage anaerobic reactor was developed. The main purpose of the study was to develop a two-stage onsite treatment system, which could become attractive from technical, economical, social and environmental viewpoints, to the technologies that are currently employed. The treatment unit consists of a cylindrical tank, where half of the volume is used as a modified septic tank and the other half as an upflow anaerobic filter. The system was operated at a hydraulic retention time of 24 h. The system was operated at ambient temperatures in laboratory-scale. During one year of continuous operation and performance evaluation, it was observed that a steady state condition was achieved after 120 days of operation without inoculation. The system was found to deliver highly satisfactory removal rates of 88.7±3% chemical oxygen demand (COD), 86.3±4% biochemical oxygen demand (BOD), and 91.4±10% total suspended solids (TSS), observed at steady state condition. It also showed a very good endurance against imposed hydraulic shock load. On account of the highly satisfactory experimental results, low cost, and no requirement of electricity, this system can be a potential alternative to the conventional septic tank in the developing countries like India. Keywords: Anaerobic system, domestic wastewater, on-site treatment, two-stage Cite this Article Meena Kumari Sharma, Kazmi AA. Performance Appraisal of Two-stage On-Site Domestic Wastewater Treatment System under Ambient Environment. Recent Trends in Civil Engineering & Technology. 2018; 8(1): 20–28p.

Effluents from on-site wastewater treatment systems can influence surface water quality, particularly when infrastructure is aging, malfunctioning, and improperly installed. Municipal wastewater often contains chemical compounds that can lead to adverse biological effects, such as reproductive impairment, in organisms that are chronically exposed. A significant number of these compounds are endocrine-disrupting chemicals. Water quality influences of on-site systems are poorly studied in semi-arid regions where instream flows are seasonally dependent on snowmelt, and when instream dilution of wastewater effluents is minimal during other times of the year. Here we examined surface water estrogenicity in low order tributaries of two unique semi-arid streams with on-site wastewater treatment systems, for which seasonal instream flow fluctuations occur in Park City, UT, USA. Water samples were collected from a total of five locations along two lotic systems downstream from active on-site treatment systems. Samples were extracted for targeted chemical analyses and to perform in vivo and in vitro bioassays with juvenile rainbow trout. Estrogenic activity was measured by quantifying the concentration and expression of vitellogenin (VTG) in plasma and liver, respectively. Plasma VTG presented elevated levels in fish exposed to water samples collected at the two sites in close proximity to on-site systems and during seasons with low stream discharge, though the levels observed did not suggest severe endocrine disruption. However, long-term exposure to these surface water could compromise the fish populations. While the sensitivity of in vitro bioassays was low and targeted chemical analyses did not identify causative compounds, the use of complementary lines of evidence (e.g., in vivo biological models) was advantageous in identifying estrogenic activity in waters influenced by effluents from on-site wastewater systems.

Global emissions linked to wastewater treatment are estimated to account for up to 1.5 % of total greenhouse gas (GHG) emissions globally. However, few studies have measured GHG emissions from domestic on-site treatment systems (DWWTSs) directly. In this study, two DWWTSs were monitored for 446 days and > 42,000 gas flux measurements were conducted using both discrete spot measurements and continuous flux chamber deployments. The observed GHG fluxes from biological activity in the soil and water phase were found to be highly spatially and temporally variable and correlated to environmental factors, water usage patterns and system design. In total, the results show that a septic tank discharging effluent into a well-designed soil treatment unit is estimated to emit a net 9.99 kg-CO2eq cap−1 yr−1, with approximately 63 %, 27 % and 10 % of the total CO2-equivalent net emissions in the form of CO2, CH4 and N2O, respectively. Emissions from the septic tank surface contributed over 50 % of total emissions and tended to be strongly underestimated by one-off discrete measurements, especially when episodic ebullitive events are to be considered. Fluxes from the soil treatment unit (STU) stemmed from both the soil surface and the vent system, but were also found to be periodically negative, i.e. net uptakes. Soil fluxes were mostly influenced by temperature but peaked regularly under conditions of rapidly changing soil water content. Vent fluxes were mostly governed by effluent quality and a low number of high emission events was responsible for the majority of total observed vent emissions. Owing to the strong overall spatial and temporal heterogeneity of observed fluxes from DWWTSs across all modules, future studies should focus on continuous deployments of a number of flux chambers over discrete measurements to accurately assess GHG emissions from on-site systems. This study also provided insights into managing GHG emissions from DWWTSs by different system configuration design, as well as indicating that the current IPCC emission factors for CH4 and N2O are significantly overestimating emissions for on-site wastewater treatment systems.

Global emissions linked to wastewater treatment are estimated to account for up to 1.5 % of total greenhouse gas (GHG) emissions globally. However, few studies have measured GHG emissions from domestic on-site treatment systems (DWWTSs) directly. In this study, two DWWTSs were monitored for 446 days and > 42,000 gas flux measurements were conducted using both discrete spot measurements and continuous flux chamber deployments. The observed GHG fluxes from biological activity in the soil and water phase were found to be highly spatially and temporally variable and correlated to environmental factors, water usage patterns and system design. In total, the results show that a septic tank discharging effluent into a well-designed soil treatment unit is estimated to emit a net 9.99 kg-CO2eq cap−1 yr−1, with approximately 63 %, 27 % and 10 % of the total CO2-equivalent net emissions in the form of CO2, CH4 and N2O, respectively. Emissions from the septic tank surface contributed over 50 % of total emissions and tended to be strongly underestimated by one-off discrete measurements, especially when episodic ebullitive events are to be considered. Fluxes from the soil treatment unit (STU) stemmed from both the soil surface and the vent system, but were also found to be periodically negative, i.e. net uptakes. Soil fluxes were mostly influenced by temperature but peaked regularly under conditions of rapidly changing soil water content. Vent fluxes were mostly governed by effluent quality and a low number of high emission events was responsible for the majority of total observed vent emissions. Owing to the strong overall spatial and temporal heterogeneity of observed fluxes from DWWTSs across all modules, future studies should focus on continuous deployments of a number of flux chambers over discrete measurements to accurately assess GHG emissions from on-site systems. This study also provided insights into managing GHG emissions from DWWTSs by different system configuration design, as well as indicating that the current IPCC emission factors for CH4 and N2O are significantly overestimating emissions for on-site wastewater treatment systems.

Most of the published studies on pharmaceutical products (PhPs) focus on their occurrence in the influent/effluent at wastewater treatment plants (WWTPs) in urban areas with high population density. In peri-urban/rural areas not collected to any WWTP, despite the lack of sewage collection, and often (poor) on-site treatment, data on PhPs occurrence in surface water bodies is scarce. In this study, we investigated the impact of onsite wastewater treatment systems on the occurrence of six PhPs, along with hydrological and hydrochemical data, in the drainage network of a peri-urban/rural area in Italy.Our results, along with data from other studies, show onsite treatment systems are a major source of PhPs. In the drainage water 76% of the analyses positively quantified the presence of PhPs, with carbamazepine and clarithromycin always quantifiable, even in scarcely inhabited areas, at generally higher concentrations of PhPs than those reported in previous studies. As a result, onsite treatment systems may cause ubiquitous, even if at low concentrations, PhPs occurrence in the aquatic systems.In order to allow data comparison, studies reporting PhPs environmental concentration values should clearly detail the urban /environmental setting (population density, presence of WWTPs) and the hydrological/hydrochemical conditions. Furthermore, the joint use of hydrochemical parameters and PhPs data may provide useful proxies for the occurrence of PhPs or to identify nitrate sources of urban origin. Discharge, T, EC and ORP values may help understanding relevance of mixing and, then, the importance of dilution processes in reducing PhPs concentration.The occurrence of PhPs in surface water has to be duly considered in order to protect the aquatic ecosystems and groundwater, and the use of such water for safe irrigation purposes. Further treatment trains based on the concept of nature-based solutions (i.e, vegetated channels, artificial wetlands) could constitute a valuable solution exploiting the soil–water-plant continuum around main residential areas in order to enhance degradation processes.

Management of onsite wastewater is an important local issue. The United States EnvironmentalProtection Agency (EPA) has outlined five models of onsite management in guidelines for localcommunities to decide which level and which components of each level are appropriate for localcircumstances. The City of Malibu, California, is implementing the first three of these models(inventory of onsite system, management through maintenance contracts, and managementthrough operating permits) on a risk-based approach. The City of Malibu has a population ofapproximately 13,000 people with 23 miles of coastline and world renowned beaches. There areroughly 6,000 onsite systems in Malibu located along the coast, in canyons, or upland sites.Approximately 400 of these systems are either commercial or serving multifamily (greater than 2units) residential dwellings. Advanced treatment systems have been utilized within the past sixyears and the city initially utilized a maintenance contract approach for managing these systems.How does a community of this size effectively manage onsite systems and apply the EPAguidelines? The City of Malibu has made those decisions and is currently in the second year ofimplementing their management program. The City is now implementing a state grant funded program to improve coordination between theRegional Board and the City of Malibu using shared information and promoting bettercommunication regarding onsite wastewater treatment systems where there is overlappingjurisdiction. The City is developing a web-based information management program to facilitatethe process of managing onsite systems. Malibu has three levels of onsite wastewater treatment system management: Model 1 (inventoryand voluntary homeowner management) for all onsite systems in the City; Model 2 (maintenancecontracts) for existing and functional advanced treatment systems serving single family andduplex residential properties; Model 3 (operating permits) for all commercial and multifamilyoccupancies and new, repaired or renovated advanced treatment systems. The goal is to phase outthe maintenance contract program, and eventually have operating permits for all systems basedon risk. This approach can be replicated by other communities especially in coastal areas wherethe need for water quality protection is high and onsite systems are viewed as a long termsolution for wastewater management.

When onsite treatment and disposal systems (OSTDS) are not properly sited or installed, they can be a potential risk to public health and a source of environmental degradation. There are estimated to be over 2.3 million onsite sewage treatment and disposal systems currently in use in Florida, serving approximately 4.5 million people. These systems discharge over 426 million gallons of treated effluent per day in to the subsurface soil environment. Nearly 40% of those systems are found along Florida's southeastern Atlantic coastline. Onsite system failure can result in problems that include direct exposure to inadequately treated sewage, ground and surface water pollution, and contamination of shellfish beds. Throughout the State of Florida, where the water table is high, septic tanks have proven to be problematic from a water resource perspective. Impacts are traced to a lack of regulation prior to the 1980s and to high densities of septic tanks on small lots. Moreover, many of these high-density developments were historically inhabited only in the winter months when the water table is low and performance optimal. When the water table is high, septic tanks cannot operate properly because the water table is above the drainage pipes, interfering with the normal hydraulic specifications and complicating pollutant migration modeling. Thus, the potential for groundwater and surface water contamination is increased, and clearly there is a need to quantify the contribution of environmental degradation attributable to OSTDS. The research team has investigated differences in sewered and non-sewered areas in Broward and Palm Beach Counties in Florida to attempt to quantify the nutrient loading contribution from septic tanks and also to determine the extent of observed nutrient contamination from other sources in a major urban setting. Recently, a unique opportunity to study a rural area in Taylor County, allowed the research team to investigate newer tracers. Taylor County (see Figure 1) is located in Northwest Florida along the Gulf of Mexico coastline directly south of Tallahassee. The total area of the County is 789,000 acres (3,191 km 2 ), of which approximately 15% is comprised of water bodies. Taylor County has four rivers, numerous canals, creeks, and springs, and nearly 60 miles of Gulf of Mexico coastline. The major tourist attractions are fishing and scalloping, particularly from July through September. Half of its southern coast is part of the Big Bend Sea Grasses Aquatic Preserve and is classified as Outstanding Florida Waters . Prior studies have been conducted by the Suwanee River Water Management District (SRWMD) and the Taylor County Health Department (TCHD) in Taylor County to determine if water quality criteria are being met. An ongoing beach monitoring program posts advisories approximately 46% of the time due to high concentration of indicator bacteria (>400 CFU/100mL for fecal coliform, >100 CFU/100mL for Enterococcus ). Maintenance of the microbiological quality and safety of water systems used for drinking, for recreation, and for the harvesting of seafood is imperative. Contamination of these water systems can result in high risks to human health and significant economic losses due to closures of beaches and shellfish harvesting areas.

Abstract. Global emissions linked to wastewater treatment are estimated to account for up to 1.5 % of total greenhouse gas (GHG) emissions globally. However, few studies have measured GHG emissions from domestic on-site treatment systems (DWWTSs) directly. In this study, two DWWTSs were monitored for 446 d and > 42 000 gas flux measurements were conducted using both discrete spot measurements and continuous flux chamber deployments. The observed GHG fluxes from biological activity in the soil and water phase were found to be highly spatially and temporally variable and correlated to environmental factors, water usage patterns and system design. In total, the results show that a septic tank discharging effluent into a well-designed soil treatment unit is estimated to emit a net 9.99 kg-CO2eq.cap-1yr-1, with approximately 63 %, 27 % and 10 % of the total CO2-equivalent net emissions in the form of CO2, CH4 and N2O, respectively. Emissions from the septic tank surface contributed over 50 % of total emissions and tended to be strongly underestimated by one-off discrete measurements, especially when episodic ebullitive events are to be considered. Fluxes from the soil treatment unit (STU) stemmed from both the soil surface and the vent system. Soil fluxes were mostly influenced by temperature but peaked regularly under conditions of rapidly changing soil water content. Vent fluxes were mostly governed by effluent, quality and a low number of high-emission events were responsible for the majority of total observed vent emissions. Owing to the strong overall spatial and temporal heterogeneity of observed fluxes from DWWTSs across all modules, future studies should focus on continuous deployments of a number of flux chambers over discrete measurements to accurately assess GHG emissions from on-site systems. This study also provided insights into managing GHG emissions from DWWTSs by different system configuration design, as well as indicating that the current IPCC emission factors for CH4 and N2O significantly overestimate emissions for on-site wastewater treatment systems.

ity. On-site treatment systems are now an integral part of our wastewater infrastructure and are collectively referred to as decentralized wastewater systems. Decentralized wastewater technology and management refers to wastewater treatment and dispersal systems from the individual on-site treatment system (septic systems) to small community collection and treatment systems (cluster systems) and includes the process involved in siting, installing, operating and maintaining the systems. These systems rely upon land application by surface or subsurface dispersal and proper treatment of the wastewater. They allow the treated wastewater to re-enter the hydrologic cycle close to where the potable water was removed. Often, as in the case of an individual system, this is less than a few hundred feet. They are considered to be non-point source discharges by federal and state standards. Often septic systems are portrayed in a negative light but they are now an integral part of our wastewater infrastructure. Photo by David Lindbo and courtesy of Soil Science @ NC State's Flickr photostream.

Viral and bacterial contamination of groundwater from on-site sewage treatment systems

On-site septic tank-soil absorption systems treating domestic wastewater have contaminated groundwaters with enteric viruses and other pathogens and caused drinking waterborne outbreaks. The factors influencing pathogen transport, survival and fate at on-site wastewater treatment systems remain inadequately characterised. We studied the survival and transport of a model enterovirus (BE-1) and faecal coliform bacteria in four on-site wastewater treatment systems (three conventional and one low pressure, small pipe diameter, pumped system) located in sandy soils typical of the coastal plains. Septic system wastewaters were seeded seasonally with known amounts of BE-1 and the fate of BE-1, faecal coliforms and other wastewater constituents were followed for three months in seeded wastewaters and groundwaters of drainfield monitoring wells. BE-1 levels in seeded wastewaters declined exponentially by kinetics consistent with a 3d hydraulic residence time. BE-1 was detected in ground waters of monitoring wells as early as 1d after seeding and persisted up to two months. Virus detection in ground water was greater in winter than in summer and was positively associated with proximity to septic effluent distribution lines, drainfield soils with the lowest clay content, elevated ground water pH and shallower vadose zones. Viruses were not strongly associated with either distance from septic tank or faecal coliform levels in groundwater. Under optimum conditions, virus reductions were as high as 9 log10, but in systems with the most coarse (sand) soils and highest water tables (most shallow vadose zones), there was extensive ground water contamination by viruses and other wastewater constituents. Under some conditions, septic systems in sandy coastal plains soils can contaminate ground water with viruses and other wastewater constituents.

Wastewater from 30 onsite wastewater treatment systems was sampled during a reconnaissance field study to quantify bulk parameters and the occurrence of organic wastewater contaminants including endocrine disrupting compounds. Treatment systems represented a variety of wastewater sources and treatment processes. Receiving environments including surface water and groundwater was also sampled. Bulk parameters ranged in concentrations representative of the wide variety of wastewater sources (residential and non-residential). Organic contaminants such as sterols, surfactant metabolites, antimicrobial agents, stimulants, metal-chelating agents, and other consumer product chemicals, measured by gas chromatography/mass spectrometry were detected frequently in onsite system wastewater. Wastewater composition was unique between source type likely due to differences in source water and chemical usage. Removal efficiencies varied by engineered treatment type and physicochemical properties of the contaminant, often resulting in discharge to the soil treatment unit at ecotoxicologically relevant concentrations. Organic wastewater contaminants were detected less frequently and at lower concentrations in onsite system receiving environments. Understanding the occurrence and fate of organic wastewater contaminants in onsite wastewater treatment systems will aid in minimizing risk to ecological and human health.

Onsite wastewater treatment systems and small scale packaged wastewater treatment plants have been used on a large scale in developing and developed countries where centralized sewerage facilities are not feasible. Generally, onsite systems continuously work under significant variations in both quantity and quality of the influent wastewater. Therefore, their suitability needs to be assessed before installation and operation to ensure their suitability and sustainability. This paper aims to define a set of context-specific criteria to assist in selecting the best onsite wastewater treatment system and to break down these criteria into measurable parameters. Furthermore, the developed multi-criteria assessment tool was validated using the results of the performance monitoring of a selected wastewater treatment system. This work is important since the selection of onsite systems, in many cases, is done based on declared performance by the supplier and the costs involved.

Approximately 23 percent of the estimated 115 million occupied homes in the United States are served by onsite wastewater systems. The vast majority of onsite wastewater treatment systems include a septic tank, grease trap, or both for primary treatment. These units are efficient, simple, low-energy treatment units whose performance is critically important to the overall functioning of onsite wastewater systems. Regulations, industry standards, guidance materials and engineering texts vary widely and are often incomplete in their consideration of the factors that may influence primary unit performance in onsite systems. The objective of this research was therefore to identify, compile, analyze, and report on the existing body of work addressing the performance of primary treatment units in onsite wastewater systems and the factors impacting performance. Design, construction/installation, and maintenance issues were considered, with a goal of establishing what is known, what is not known and what future research is needed in this area. Over 700 sources of information were collected, with most reviewed and presented in this document - the white paper. A bibliographic database, which can continue to be updated into the future, was developed as a companion piece to the white paper, as a tool for researchers and practitioners. This title belongs to WERF Research Report Series ISBN: 9781780403700 (eBook) ISBN: 9781843397816 (Print)

Ultraviolet disinfection (UVD) units enhance onsite sewage systems (OSSs) in areas where conventional treatment is limited by site characteristics. Although UVD units are efficacious under testing conditions, few studies have considered their effectiveness when installed. This study used a mixed-methods approach to examine UVD unit effluent quality and determine the association between UV bulb status and fecal coliform levels. Samples from UVD units and pump chambers were tested for bacterial and physiochemical parameters. Field data were supplemented with data from retrospective compliance samples. A multivariate Tobit regression model predicted that the geometric mean (GM) fecal coliform concentration was 122% higher when the UV bulb was deficient than when it was not deficient, adjusted for other OSS deficiencies (95% CI: 36-428, p-value <0.001). The predicted GM fecal coliform concentration in malfunctioning UVD unit effluent (745 CFU/100 mL) exceeded field compliance standards (400 CFU/100 mL), and the odds of exceedance were 7.48 times higher when the UV bulb was deficient, adjusted for other OSS deficiencies (95% CI: 4.03-13.9, p-value <0.001). Despite limitations in the characterization of UV dose, the results validate the importance of UVD units to reduce bacterial loads and the need for further research into their field effectiveness.