On-site Treatment Systems Research Articles

Performance Evaluation of Nitrogen Removal Type On-site Treatment System for Domestic Wastewater

Performance Evaluation of Nitrogen Removal Type On-site Treatment System for Domestic Wastewater

Numerical estimation of nitrogen load from septic systems to surface water bodies in St. Lucie River and Estuary Basin, Florida

Nitrogen pollution is one of the most prevalent and challenging environmental problems worldwide. Wastewater treatment using onsite sewage treatment and disposal systems (aka septic systems) is one source of nitrogen sources in the environment. This study presents a numerical study for estimating nitrogen load from septic systems to surface water bodies in the St. Lucie River and Estuary Basin, Florida, USA. The load estimation is conducted using an ArcGIS-based nitrogen load estimation toolkit, a screening-level modeling software that considers key mechanisms (i.e., advection, dispersion, and denitrification) controlling nitrogen transport as well as spatial variability of model parameters (e.g., hydraulic conductivity, porosity, septic system locations, and surface water bodies). The simulated nitrogen plumes and load estimates demonstrate the importance of considering spatial variability in the load estimation for nitrogen pollution management. The load estimates are strongly correlated with nitrogen concentrations in surface water quality data, suggesting that septic systems are an important factor for water quality deterioration in the St. Lucie River. The estimates can be used directly to support Basin Management Action Plan (BMAP). Evaluating the load estimates in the BMAP context indicates that nitrogen load from septic systems is a significant nitrogen source in the St. Lucie River and Estuary Basin. It is found in this study that the load estimates depend on lengths of flow paths, groundwater flow velocities, and soil drainage conditions. These findings are useful for nitrogen pollution management in similar areas facing nitrogen pollution problems.

Achieving Successful River Restoration in Dense Urban Areas: Lessons from Taiwan

A paradigm shift in river management practice is underway, from a hard engineering-dominated emphasis that endeavours to control water, to a multi-functionality-framed approach that strives to restore a river’s ecology, scenery and ecosystem services. In Taiwan, the Laojie River in Taoyuan City, where a channelized and piped urban river was recently transformed into an accessible, linear green infrastructure feature, is widely regarded as the first extensive and successful river restoration project in Taiwan’s densely-urbanized, flood-prone areas, yet its actual performance is rarely examined in any depth. Through in-depth interviews, fieldwork and a review of government documents, this paper presents findings on the practical factors involved in the practice of river restoration and their implications for urban river management. First, local people support river restoration with de-culverting, but potential flooding is a concern that results from different flood-risk perceptions and ineffective flood-risk communication between the government and public. Second, a mix of hard and soft edges to the watercourse improves the riverside landscapes in a densely-urban, flood-prone area. Third, due to a lack of basin-wide supporting sanitary sewer systems, a combination of on-site gravel contact oxidation treatment systems and riverside sewage-intercepting facilities still fails to improve the river water quality. Fourth, people’s positive attitudes towards river restoration are largely associated with landscape aesthetics and recreational value, rather than water quality and biodiversity. It is revealed that using the Cheonggyecheon Stream in South Korea as a frame for river restoration seems effective in providing local people with an example of successful river restoration, based mainly on flood prevention and recreational and aesthetic improvement. Moreover, the effective flood-risk communication is mainly reliant on an intelligible presentation of related information to the general public. Practical, continuous and extensive public participation, with various types of involvement and resources along with a solid system of social objectives by which to assess the outcome, is central to the social aspect of river restoration.

Ensuring safe reuse of residential wastewater: reduction of microbes and genes using peat biofilter and batch chlorination in an on-site treatment system.

A batch chlorination system was optimized for on-site wastewater treatment and reuse system (OWRS) and its efficiency was evaluated for reducing viruses, protozoa, bacteria and antimicrobial resistance in cold and warm seasons. The OWRS performance in reducing microbial contaminants was determined by assessing three different faecal indicators (Escherichia coli, F-specific coliphages and Clostridium perfringens for measuring the disinfection efficiency of bacteria, viruses and spore-formers and surrogate for protozoa, respectively) using culture-based methods. Quantitative PCR was used to quantify pathogenic bacteria (Shiga-toxin-producing E.coli (STEC), Campylobacter spp., and Arcobacter spp.), a human-associated faecal marker (gyrB), and tetracycline resistant bacteria (tetQ). The levels of E.coli, coliphages and Cl.perfringens showed 5·4, 2·3, 2·5 log reduction, respectively, upon disinfection. In the final effluents, coliphages (1·7×102 PFU 100ml-1 ) and Cl.perfringens (3·4CFU100ml-1 ) were detected in 80 and 100% of the samples, but E.coli was not found. The removal and inactivation of E.coli and Cl.perfringens were not significantly different across the seasons, however, efficacy of removal and inactivation of F-specific coliphage was significantly reduced during the winter/spring season compared to the summer/autumn season (P=0·009). The reduction of Arcobacter, gyrB and tetQ by 3·1, 2·3 and 2·3 log, respectively, was mostly due to peat biofiltration under the study conditions. This study demonstrated that peat biofiltration was the most important step of the OWRS to remove microbes and genes from wastewater before spray irrigation of the effluents. The irrigation system is not suitable for edible crops because of the potential presence of residual pathogens. On-site wastewater treatment systems are a practical option for reusing the wastewater for landscape, especially for those areas where geological and seasonal limitations impact the removal of microbial contaminants by soil infiltration.

Infectious bacterial pathogens, parasites and pathological correlations of sewage pollution as an important threat to farmed fishes in Egypt

This paper is a part of a multi-disciplinary research “Application of Decentralized On-Site Water Treatment System in Egypt for Use in Agriculture and Producing Safe Fish and Animal Proteins”.The project aimed to investigate the environmental impact of implementing sewage water before and after treatment using the effluent of the on-site decentralized Japanese' Johkasou system, in agriculture and producing fish protein. The aim is to establish such system in Egypt to strengthen the sanitary conditions of water resources. In the present study, the impact of the sewage pollution in some fish farms at El-Fayyum, Port Said and El-Dakahlia governorates in Egypt was carried out. Water and fish (Oreochromis niloticus and Mugil cephalus) samples were collected from private fish farms of such localities. Bacteriological and chemical examination of water samples revealed the existence of coliforms and many other bacterial species of significant human health hazards. The chemical parameters of water showed a marked deviation from normal levels while examination of fish flesh specimens indicated contamination with Streptococcus Sp., Staphylococcus Sp., and Salmonella in all examined localities. Other bacterial isolates of human health importance (Morganella morganii, Pseudomonas cepacia and Enterococcos durans) were identified. The parasitological examination revealed the presence of encysted metacercariae (EMC); Diplostomatidae, Prohemistomatidae and Heterphyidae. Moreover, two protozoan parasites (Mxyoboulus tilapiae and Ichthyophthirius multifilis) were also recorded. The histopathological examination revealed mild tissue reaction in case of bacterial infection and severe pathological lesions in different organs in case of EMC infection. Lamellar hyperplasia and mononuclear cell infiltration in branchial tissue was common findings. In skeletal muscles, atrophy of muscle fibres, myolysis and myophagia were detected.

Performance evaluation of an Integrated On-site Greywater Treatment System in a tropical region

Integrated On-site Greywater Treatment System (IOGTS) with primary (settling/filtration), secondary (constructed wetland) and tertiary (adsorption) treatment was used to treat greywater from hostel. A field scale IOGTS was constructed for hostel located in Sakharale, District Sangli (M.S.) India. The performance evaluation of IOGTS was carried out for a study period of one year. The quality parameters used to assess feasibility of disposal for land application were COD, TKN, suspended solids, and pathogens. The effect of hydraulic loading rate (HLR), Hydraulic Retention Time (HRT) and Organic Loading Rate (OLR) on performance of the system was also studied. A consistent performance (30% COD removal and 70% turbidity removal) was observed in upflow-downflow filter throughout the study. Secondary treatment in IOGTS was evaluated for HLR (10–100mm/d) and OLR (10–350kg COD/ha.d). HLR (40mm/d) and OLR (170kg COD/ha.d) showed a better removal efficiency of COD. Overall performance of IOGTS for COD, TKN and pathogen removal was observed to be 70%, 70% and 85% respectively. Therefore, IOGTS can be considered to be an appropriate treatment option to treat greywater to satisfy effluent standards for its reuse in land application.

The Investigation and Designing of an Onsite Grey Water Treatment Systems at Hazrat-e-Masoumeh University, Qom, IRAN

Limited water supplies remind the environmental ethics of recovery and reuse of limited resources. One of the interesting options in this context is Grey water. Grey water is wastewater originating from showers, baths, bathroom sinks, kitchen sinks and laundries. It does not include toilet or garbage wastes, or wastewater contaminated by soiled diapers. Despite the fact that it may include a complex mixture of organic matter, suspended solids, bacteria and common household chemicals, when used wisely and in a manner that is protective of public health and the environment, it can help preserve limited water supplies.Qom Province is located in the central part of Iran, at the Latitude and the Longitude of 34° 38’ 24N and 50° 52’ 35 E respectively. The city of Qom is the 7th most populated city of Iran. With an altitude of 933 meters above the sea level and a location adjacent to two great deserts Qom has a very hot and dry weather. The salt lake (Daryacheh-ye Namak) in the east of the city has caused the ground to be usually arid and parched. Due to proximity to desert region, the climatic changes and the low value of precipitation, water resources are under pressure, and under such harsh conditions, water is very precious. The onsite wastewater treatment systems can reduce the water crisis. To this end the Hazrat-e-Masoumeh University was selected as a pilot to investigate the feasibility of reusing the produced grey water.Based on studies undertaken to propose a grey water treatment system, the Hazrat-e-Masoumeh University has recommended the application of trickling filters with suspended plastic media. In this method, waste particles (if existing) are first removed from the system by a 1cm mesh screen. Then the grey water is conducted to a buried septic tank and the resulting water is pumped to a trickling filter containing suspended plastic media and the sludge, amounting to thrice the discharge of the pumped water is returned to the septic tank. After passing through the trickling filter, water is led to the settling tank, where the produced sludge is settled. Finally a chlorination system is used to disinfect the treated effluent. It should be noted that the kitchen effluent needs to be pre-treated to remove fat and 4. Furthermore, this project is the first report of designing an onsite grey water treatment system in a university in Iran.

Increased Effluent Dosage Effects on On-Site Wastewater Treatment Systems of Differing Architecture Type

Approximately 20% of homes nationwide use an on-site treatment system as a form of household wastewater management. However, approximately 10% to 20% of on-site treatment systems malfunction each year, many of which have either failed or exceeded the soil’s long-term acceptance rate (LTAR), causing environmental and human health risks. The objective of this field study was to evaluate the effects of soil condition (e.g., wet and dry) and product architecture type [i.e., chamber, gravel-less-pipe (GLP), polystyrene-aggregate, and pipe-and-aggregate] on in-product solution storage and biomat thickness in a profile-limited soil in northwest Arkansas under increased loading rates and to estimate the LTAR for each product. During Phase I of this study (March 13 to October 4, 2013), effluent loading rates were approximately doubled, while rates were approximately quadrupled during Phase II (October 8, 2013 to May 29, 2014), from the maximum allowable loading rate for each product. The pipe-and-tire-chip, 46-cm-wide trench pipe-and-gravel, and the 25-cm diameter GLP products had the greatest (p < 0.001), while the 31-cm-width and the 5.4-m-long chambers had the lowest (p < 0.001) in-product solution storage during wet-soil conditions of Phase I monitoring. The 25-cm diameter GLP product had the greatest (p < 0.001), while the 61-cm-width, 5.4-m-long chamber had the lowest (p < 0.001) in-product solution storage during Phase II. Results of this study indicate that some alternative products may be able to effectively handle effluent loading rates in excess of those currently allowed by the State of Arkansas. Further research will be required to confirm these interpretations.

Septic Systems as a ‘Green’ Technology

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.

Monitoring infiltration under a real on-site treatment system of domestic wastewater and evaluation of soil transfer function (Paris Basin, France)

The problem of evacuation of treated domestic wastewater has been investigated through a field study on a real undrained on-site treatment system (UOSTS). This system imposes a special mode of infiltration into the soil which is irregular. To characterize the hydraulic properties of this type of flow, soil texture, organic matter content and in situ saturated hydraulic conductivity (Ks) were measured for each 15 m2 of soil under the bottom of the UOSTS. In addition, the variation of water table and rainfall and the evolution of soil moisture and matrix potential were monitored using the sensors implanted under the system. The mean of the measured Ks is 100 times higher than values deduced from empirical pedotransfer functions based on the soil matrix properties. The measured Ks varies greatly in the 15 m2 area. Moreover, large and variable quantities of stone fragments (>2 mm) were found in the soil samples. These results suggest that a heterogeneous flow may occur in the stony soil via the macropores which shortcut the soil matrix. Indeed, according to their position, a non-uniform reaction of the sensors to the infiltration of treated wastewater was observed. In addition, two daily periodic peaks of water consumption in the house have been detected by the water content and tensiometer probes, confirming that the saturation rate is controlled by infiltration and not the water table.

The question of pathogen quantification in disinfected graywater

Graywater (GW) reuse for irrigation is recognized as a sustainable solution for water conservation. One of the major impediments to GW reuse is the presence of pathogenic microorganisms. This study monitored three similar on-site GW treatment systems bi-monthly over the course of a year to compare the presence of pathogens and indicators in raw, biologically treated, and biologically treated and disinfected [by chlorine and ultraviolet light (UV)] GW. The systems were designed to allow the testing of the same batch (collection) of water as it passed through the treatment chain. The samples were analyzed using standard culture-dependent methods and the data were compared to culture-independent DNA-based methods. Results suggested that the presence and abundance of fecal coliforms, Escherichia coli, Salmonella enterica, Enterococcus spp., Staphylococcus aureus and Pseudomonas aeruginosa differ among the various GW streams (e.g. raw, biologically treated, and disinfected). The culture-dependent analyses suggested that both chlorine and UV inactivate most of the bacteria tested in the biologically treated GW, albeit at different efficiencies. Conversely, the DNA-based analyses indicated no significant differences in pathogenic bacterial abundance between the biologically treated GW with or without disinfection. To better understand the discrepancies between the results, we repeated the analysis in the laboratory under controlled conditions using Enterococcus faecalis as a model bacterium and obtained similar results. We suggest that disinfection of biologically treated GW with chlorine or UV is effective for treating pathogens, but that the inactivation efficiency cannot be estimated by DNA-based qPCR.

The evaluation of applicability for development of advanced package system (BioKube) for sewage treatment

Nowadays, more developing countries are facing the serious challenge of treating increasing number of decentralized domestic sewage in rural areas. Domestic sewage in rural areas that do not have public sewers must rely on on-site treatment system to manage wastewater. Therefore, new sewage treatment system for domestic sewage is a social concern in rural areas. In this respect, this study aimed to characterize treated domestic sewage by applying high-flux flat membrane to BioKube reactor consisted of aerobic bio-film media with the automatic control function. The BioKube reactor is separated into four chambers and each chamber contains approximately 584, 157, 487 and 118 L of wastewater, respectively. The removal efficiencies of CODCr, BOD5, SS, T-N, NH4+-N and T-P were reached 81.5, 84.8, 81.7, 38.3, 84.6 and 40.1%, respectively at a hydraulic retention time of 22 h. In addition to, T-P decreased from 4.03 to 0.01 mg/L by installation of coagulation-membrane reactor on the latter part and SS concentration decreased by approximately 99.9%.

Socio-cultural acceptance of appropriate technology: Identifying and prioritizing barriers for widespread use of the urine diversion toilets in rural Muslim communities of Bangladesh

The Urine Diversion Dehydration Toilet (UDDT) is an important technology which could raise the standard of living for the poorest areas in low-income countries. It is a resource reuse oriented sanitation technology and onsite treatment system for human wastes. It can be one option to solve global sanitation problems by breaking socio-cultural taboos in water, sanitation and hygiene in low income countries. In this study, both qualitative and quantitative data were collected to assess the socio-cultural acceptance and replication of UDDTs in rural Muslim communities in Bangladesh. The study results showed that UDDTs have been generally accepted by almost all users and to some extent by non-users. There were some social and cultural barriers to accepting UDDTs in the study area. Major drivers, which need to be further explored and researched, were found to heavily influence the acceptance and replication of UDDTs. Importantly it was found that the biggest challenge to the acceptance of this technology was not the replication of UDDTs or socio-cultural barriers. Instead, the biggest challenges were high construction cost, dependence on subsidies from donors and a lack of financial contribution from the government. It was found that even though socio-cultural barriers are important, identifying the proper drivers, alternative financial mechanisms (such as involvement of micro-finance organizations), the involvement of community based organizations, and the active participation of local governments were the top priorities. Identifying these factors and prioritizing them is essential for deploying UDDTs and similar technologies throughout other parts of the world. This study provides insight into technologies that are critical for development in low income countries as well as the characterization of socio-cultural factors that are involved at this intersection of technology in society.

Values of decentralized systems that avoid investments in idle capacity within the wastewater sector: A theoretical justification

In this work, the values of decentralized (onsite) systems that avoid investments in idle capacity within wastewater plans are quantitatively justified using the specific net present value (SNPV) approach. SNPV is a currently proposed criterion in environmental engineering economics that is defined as the net present value of the cost per unit of service or per population equivalent (PE). The SNPV approach was reintroduced with bugs fixed and then applied to the economic analysis of the capital and operating costs of one-stage completed central plants, stage-expanded central plants, and decentralized treatment facilities. The results show that under a demand growth scenario, the central plant will inevitably reach idle capacity, which can be reduced by a staged expansion. However, the staged expansion plan will lose the economies of scale and, hence, is only viable under projections of a low or moderate price inflation rate or high demand growth rate. Onsite treatment systems can theoretically achieve 100% utilization. Assuming that the capital costs per PE of the onsite and central systems are equal, the former is economically favorable in most cases of price inflation as a result of its cost saving on idle capacity. Onsite treatment systems can be viable even though their capital expenditures per PE are higher than that of a comparable centralized option as to a capital investment. This finding suggests wide opening of onsite technology choices. Use of the SNPV showed that average operating expenses of centralized plants decrease as demand growth rates increase as a benefit of economies of scale, whereas those of onsite treatment systems depend only on price inflation. Semi-decentralized systems feature both the financial advantage of the onsite system (capital investment) and the superiority of centralized systems (operation and maintenance); thus, it is worth consideration. The results of this study illustrate not only the value of decentralized systems but also the value of the SNPV approach in the planning of wastewater services, especially in areas undergoing high demand growth.

A comparison of the suitability of different willow varieties to treat on-site wastewater effluent in an Irish climate

Short rotation coppiced willow trees can be used to treat on-site wastewater effluent with the advantage that, if planted in a sealed basin and sized correctly, they produce no effluent discharge. This paper has investigated the evapotranspiration rate of four different willow varieties while also monitoring the effects of three different effluent types on each variety. The willow varieties used are all cultivars of Salix viminalis. The effluents applied were primary (septic tank) effluent, secondary treated effluent and rain water (control). The results obtained showed that the addition of effluent had a positive effect on the evapotranspiration. The willows were also found to uptake a high proportion of the nitrogen and phosphorus from the primary and secondary treated effluents added during the first year. The effect of the different effluents on the evapotranspiration rate has been used to design ten full scale on-site treatment systems which are now being monitored.

The Effect of Hydraulic Loading Rate and Influent Source on the Binding Capacity of Phosphorus Filters

Sorption by active filter media can be a convenient option for phosphorus (P) removal and recovery from wastewater for on-site treatment systems. There is a need for a robust laboratory method for the investigation of filter materials to enable a reliable estimation of their longevity. The objectives of this study were to (1) investigate and (2) quantify the effect of hydraulic loading rate and influent source (secondary wastewater and synthetic phosphate solution) on P binding capacity determined in laboratory column tests and (3) to study how much time is needed for the P to react with the filter material (reaction time). To study the effects of these factors, a 22 factorial experiment with 11 filter columns was performed. The reaction time was studied in a batch experiment. Both factors significantly (α = 0.05) affected the P binding capacity negatively, but the interaction of the two factors was not significant. Increasing the loading rate from 100 to 1200 L m−2 d−1 decreased P binding capacity from 1.152 to 0.070 g kg−1 for wastewater filters and from 1.382 to 0.300 g kg−1 for phosphate solution filters. At a loading rate of 100 L m−2 d−1, the average P binding capacity of wastewater filters was 1.152 g kg−1 as opposed to 1.382 g kg−1 for phosphate solution filters. Therefore, influent source or hydraulic loading rate should be carefully controlled in the laboratory. When phosphate solution and wastewater were used, the reaction times for the filters to remove P were determined to be 5 and 15 minutes, respectively, suggesting that a short residence time is required. However, breakthrough in this study occurred unexpectedly quickly, implying that more time is needed for the P that has reacted to be physically retained in the filter.

Multi-objective evolutionary optimization for greywater reuse in municipal sewer systems

Sustainable design and implementation of greywater reuse (GWR) has to achieve an optimum compromise between costs and potable water demand reduction. Studies show that GWR is an efficient tool for reducing potable water demand. This study presents a multi-objective optimization model for estimating the optimal distribution of different types of GWR homes in an existing municipal sewer system. Six types of GWR homes were examined. The model constrains the momentary wastewater (WW) velocity in the sewer pipes (which is responsible for solids movement). The objective functions in the optimization model are the total WW flow at the outlet of the neighborhoods sewer system and the cost of the on-site GWR treatment system. The optimization routing was achieved by an evolutionary multi-objective optimization coupled with hydrodynamic simulations of a representative sewer system of a neighborhood located at the coast of Israel. The two non-dominated best solutions selected were the ones having either the smallest WW flow discharged at the outlet of the neighborhood sewer system or the lowest daily cost. In both solutions most of the GWR types chosen were the types resulting with the smallest water usage. This lead to only a small difference between the two best solutions, regarding the diurnal patterns of the WW flows at the outlet of the neighborhood sewer system. However, in the upstream link a substantial difference was depicted between the diurnal patterns. This difference occurred since to the upstream links only few homes, implementing the same type of GWR, discharge their WW, and in each solution a different type of GWR was implemented in these upstream homes. To the best of our knowledge this is the first multi-objective optimization model aimed at quantitatively trading off the cost of local/onsite GW spatially distributed reuse treatments, and the total amount of WW flow discharged into the municipal sewer system under unsteady flow conditions.

エコファン（ECO-FAN）等による浸出水簡易浄化システムに関する研究（その１）

エコファン（ECO-FAN）等による浸出水簡易浄化システムに関する研究（その１）

Support of sustainable management of nitrogen contamination due to septic systems using numerical modeling methods

Nitrogen contamination is a serious concern to sustainable environmental management, and one important source of nitrogen contaminant is due to wastewater treatment using onsite sewage treatment and disposal systems (OSTDS, a.k.a., septic systems). This paper presents a study in which numerical modeling is used to support sustainable decision-making and management of nitrogen contamination by utilizing a recently developed GIS-based software, VZMOD, a Vadose Zone MODel for simulating nitrogen transformation and transport in vadose zone between drainfield of septic systems and water table. VZMOD is based on a physical model of unsaturated flow and nitrogen transformation and transport, and the model is solved numerically using the finite element methods. This is the major difference between VZMOD and other GIS-based software of nitrogen modeling. Using GIS techniques, VZMOD considers spatial variability of a number of hydrogeologic parameters such as hydraulic conductivity and porosity. A unique feature of VZMOD is that VZMOD addresses spatial variability of water table by using VZMOD together with ArcNLET, an ArcGIS-based software developed to simulate groundwater flow and nitrate load from septic systems to surface water bodies. VZMOD is designed to execute in different modes to be compatible with different levels of data availability in various management projects of nitrogen contamination. This paper presents an application of VZMOD at a neighborhood with hundreds of septic systems and heterogeneous hydraulic conductivity, porosity, and water table depth. The modeling results indicate that using septic systems at the considered neighborhood is unsustainable and more management means are necessary.

Comparative analysis of effluent water quality from a municipal treatment plant and two on-site wastewater treatment systems

Though decentralized on-site technologies are extensively employed for wastewater treatment around the globe, an understanding of effluent water quality impairments associated with these systems remain less understood than effluent discharges from centralized municipal wastewater treatment facilities. Using a unique experimental facility, a novel comparative analysis of effluent water quality was performed from model decentralized aerobic (ATS) and septic (STS) on-site wastewater treatment systems and a centralized municipal wastewater treatment plant (MTP). The ATS and STS units did not benefit from further soil treatment. Each system received common influent wastewater from the Waco, Texas, USA Metropolitan Area Regional Sewerage System. We tested the hypothesis that MTP effluent would exhibit higher water quality than on-site effluents, based on parameters selected for study. A tiered testing approach was employed to assess the three effluent discharges: select routine water quality parameters (Tier I), whole effluent toxicity (Tier II), and select endocrine-active compounds (Tier III). Contrary to our hypothesis, ATS effluent was not statistically different from MTP effluents, based on Tier I and III parameters, but reproductive responses of Daphnia magna were slightly more sensitive to ATS than MTP effluents. STS effluent water quality was identified as most degraded of the three wastewater treatment systems. Parameters used to assess centralized wastewater treatment plant effluent water quality such as whole effluent toxicity and endocrine active substances appear useful for water quality assessments of decentralized discharges. Aerobic on-site wastewater treatment systems may represent more robust options than traditional septic systems for on-site wastewater treatment in watersheds with appreciable groundwater – surface water exchange.