Septic Tank Systems Research Articles

Temporal variability in domestic point source discharges and their associated impact on receiving waters

Discharges from the widely distributed small point sources of pollutants such as septic tanks contribute to microbial and nutrient loading of streams and can pose risks to human health and stream ecology, especially during periods of ecological sensitivity. Here we present the first comprehensive data on the compositional variability of septic tank effluents (STE) as a potential source of water pollution during different seasons and the associated links to their influence on stream waters. To determine STE parameters and nutrient variations, the biological and physicochemical properties of effluents sampled quarterly from 12 septic tank systems were investigated with concurrent analyses of upstream and downstream receiving waters. The study revealed that during the warmer dryer months of spring and summer, effluents were similar in composition, as were the colder wetter months of autumn and winter. However, spring/summer effluents differed significantly (P<0.05) from autumn/winter for concentrations of biological oxygen demand (BOD), arsenic, barium (Ba), cobalt, chromium, manganese, strontium (Sr), titanium, tungsten (W) and zinc (Zn). With the exception of BOD, Ba and Sr which were greater in summer and spring, the concentrations of these parameters were greater in winter. Receiving stream waters also showed significant seasonal variation (P≤0.05) in alkalinity, BOD, dissolved organic carbon, sulphate, sulphur, lithium, W, Zn and Escherichiacoli abundance. There was a clear significant influence of STE on downstream waters relative to upstream from the source (P<0.05) for total suspended solids, total particulate P and N, ammonium-N, coliforms and E. coli. The findings of this study found seasonal variation in STE and place effluent discharges as a factor affecting adjacent stream quality and call for appropriate measures to reduce or redirect STE discharges away from water courses.

An alternative approach for municipal wastewater management: Technology options for small and medium towns

In India, and most other developing countries of Asia and Africa, the urban, peri-urban and rural communities suffer from serious lack of sustainable wastewater and sanitation facilities. Unlike in the developed countries, the standard practice of human excreta and wastewater disposal system (sewerage) is not functional in most urban communities. The Western model sewerage system is largely unaffordable for most communities. The problem is extremely serious and critical, in small and medium towns. The septic tank system, tried in many urban localities, also faces serious problems in operation and maintenance. This paper reviews the Indian scenario in respect of urban wastewater and sanitation management, with particular reference to the problems of small and medium towns, and describes an alternative approach for sustainable human excreta and wastewater disposal systems that could be affordable and sustainable for small and medium towns in India.

Modified Septic Tank Treatment System

Water pollution is a major global problem. One of the main causes of ground water contamination is the effluent from septic tanks. Treatment of domestic wastewater using conventional septic tank is found to be inefficient leading to increased soil and ground water contamination. It's very important to protect surface and ground water from contamination. So there is a need for improving conventional septic tank. The purpose of this study was to investigate the effect of a modified septic tank system for treating domestic wastewater. Modified septic tank system is a simple means of treating domestic wastewater using the treatment mechanisms such as anaerobic digestion and disinfection. The effect of vertical baffles coupled with an anaerobic reactor on septic tank system was analysed. The reactor selected for the study consists of copper modified zeolite as an adsorbent which will also act as filter media on which attached growth process takes place. The results showed that vertical baffled septic tank(VBST) coupled with zeolite filter shows a good treatment system. The results also showed that vertical baffled septic tank coupled with zeolite filter with disinfection shows a removal of 99.99% total coliforms, 99.57% of TSS, 46.83% Ammonia nitrogen, 31.08% of nitrate nitrogen, 48.39% of total kjeldahl nitrogen, 94.4% of BOD and 71.74% of Phosphates. This study focuses on an economical and efficient decentralized treatment method for treating domestic waste water.

물 부족국가에서 활용가능한 정화조의 최적모형 개발

Abstract This study was carried out to evaluate the performance of a lab-scale novel septic tank system for improving the conventional septic tank in the developing countries of water shortages. The lab-scale novel septic tank system consists of sepetic tank, aeration tank with HBC-ring, and sand filter. Optimum HRT was reguired about 1.5days to get a total COD removal efficiency of 90%, COD, BOD and SS removal efficiency was about 70%, 60%, and 85% in sepetic tank only. The structure of sepetic tank with two stages results in the high removal efficiency of organic matter. When sepetic tank, aeration tank, and sand filter were more than HRT 1.5days, 18hrs, and 12hrs, respectively, final effluent was less than 20 mg/L of BOD, 14 mg/L of SS, so that there is a high potential of its use for reusing water in flush toilet. There is no significant effect of HRT change on nu trient removal. Total nitrogen removal efficiency was about 40%, final effluent was 30~40 mg/L of TN, total phosphorus removal efficiency was about 11~25%, final effluent was 9~12 mg/L of TP. Because there is very small amounts of organic nitrogen and phosphorus in effluent, it was possible to reuse water for agricultural use.

Norovirus Outbreak Associated With a Natural Lake Used for Recreation—Oregon, 2014

Norovirus Outbreak Associated With a Natural Lake Used for Recreation—Oregon, 2014

Understanding the transformation, speciation, and hazard potential of copper particles in a model septic tank system using zebrafish to monitor the effluent.

Although copper-containing nanoparticles are used in commercial products such as fungicides and bactericides, we presently do not understand the environmental impact on other organisms that may be inadvertently exposed. In this study, we used the zebrafish embryo as a screening tool to study the potential impact of two nano Cu-based materials, CuPRO and Kocide, in comparison to nanosized and micron-sized Cu and CuO particles in their pristine form (0-10 ppm) as well as following their transformation in an experimental wastewater treatment system. This was accomplished by construction of a modeled domestic septic tank system from which effluents could be retrieved at different stages following particle introduction (10 ppm). The Cu speciation in the effluent was identified as nondissolvable inorganic Cu(H2PO2)2 and nondiffusible organic Cu by X-ray diffraction, inductively coupled plasma mass spectrometry (ICP-MS), diffusive gradients in thin-films (DGT), and Visual MINTEQ software. While the nanoscale materials, including the commercial particles, were clearly more potent (showing 50% hatching interference above 0.5 ppm) than the micron-scale particulates with no effect on hatching up to 10 ppm, the Cu released from the particles in the septic tank underwent transformation into nonbioavailable species that failed to interfere with the function of the zebrafish embryo hatching enzyme. Moreover, we demonstrate that the addition of humic acid, as an organic carbon component, could lead to a dose-dependent decrease in Cu toxicity in our high content zebrafish embryo screening assay. Thus, the use of zebrafish embryo screening, in combination with the effluents obtained from a modeled exposure environment, enables a bioassay approach to follow the change in the speciation and hazard potential of Cu particles instead of difficult-to-perform direct particle tracking.

Using high-resolution phosphorus data to investigate mitigation measures in headwater river catchments

Abstract. This study reports the use of high-resolution water quality monitoring to assess the influence of changes in land use management on total phosphorus (TP) transfers in two 5 km2 agricultural sub-catchments. Specifically, the work investigates the issue of agricultural soil P management and subsequent diffuse transfers at high river flows over a 5-year timescale. The work also investigates the phenomenon of low flow P pollution from septic tank systems (STSs) and mitigation efforts – a key concern for catchment management. Results showed an inconsistent response to soil P management over 5 years with one catchment showing a convergence to optimum P concentrations and the other an overall increase. Both catchments indicated an overall increase in P concentration in defined high flow ranges. Low flow P concentration showed little change or higher P concentrations in defined low flow ranges despite replacement of defective systems and this is possibly due to a number of confounding reasons including increased housing densities due to new-builds. The work indicates fractured responses to catchment management advice and mitigation and that the short to medium term may be an insufficient time to expect the full implementation of policies (here defined as convergence to optimum soil P concentration and mitigation of STSs) and also to gauge their effectiveness.

Assessment of the impact of traditional septic tank soakaway systems on water quality in Ireland.

One of the key threats to groundwater and surface water quality in Ireland is the impact of poorly designed, constructed or maintained on-site wastewater treatment systems. An extensive study was carried out to quantify the impact of existing sites on water quality. Six existing sites, consisting of a traditional septic tank and soakaway system, located in various ranges of subsoil permeabilities were identified and monitored to determine how well they function under varying subsoil and weather conditions. The preliminary results of the chemical and microbiological pollutant attenuation in the subsoil of the systems have been assessed and treatment performance evaluated, as well as impact on local surface water and groundwater quality. The source of any faecal contamination detected in groundwater, nearby surface water and effluent samples was confirmed by microbial source tracking. From this, it can be seen that the transport and treatment of percolate vary greatly depending on the permeability and composition of the subsoil.

Application of On-Site Wastewater Treatment in Ireland and Perspectives on Its Sustainability

The wastewater of one third of Ireland’s population is treated on-site using domestic treatment systems (DWWTSs) that usually consist of a septic tank and soil attenuation system. Within the past four years, the legislative framework for these systems has undergone a major change with a registration and inspection regime being introduced to identify legacy sites that will require remediation work, particularly in areas of the country underlain by subsoils of very low permeability. Against this background this study aims to assess the overall sustainability of existing DWWTSs as well as alternative treatment and disposal options. The results show that main CO2eq emissions are from the methane production in septic tanks. The reduced methane production in mechanically aerated secondary treatment systems was found to counterbalance the related emissions due to the additional energy requirements. In contrast, septic tank systems have the lowest construction and operational costs representing the most economically sustainable solution. Pressurised disposal systems are slightly more expensive but have the potential to reduce environmental impact on surface water and reduce greenhouse gas emissions. Clustered decentralised treatment solutions could be environmentally and economically sustainable but ownership, management and related financial and legal issues will need to be addressed and developed.

The Water Quality of the River Enborne, UK: Observations from High-Frequency Monitoring in a Rural, Lowland River System

This paper reports the results of a 2-year study of water quality in the River Enborne, a rural river in lowland England. Concentrations of nitrogen and phosphorus species and other chemical determinands were monitored both at high-frequency (hourly), using automated in situ instrumentation, and by manual weekly sampling and laboratory analysis. The catchment land use is largely agricultural, with a population density of 123 persons km−2. The river water is largely derived from calcareous groundwater, and there are high nitrogen and phosphorus concentrations. Agricultural fertiliser is the dominant source of annual loads of both nitrogen and phosphorus. However, the data show that sewage effluent discharges have a disproportionate effect on the river nitrogen and phosphorus dynamics. At least 38% of the catchment population use septic tank systems, but the effects are hard to quantify as only 6% are officially registered, and the characteristics of the others are unknown. Only 4% of the phosphorus input and 9% of the nitrogen input is exported from the catchment by the river, highlighting the importance of catchment process understanding in predicting nutrient concentrations. High-frequency monitoring will be a key to developing this vital process understanding.

Reduced nutrient pollution in a rural stream following septic tank upgrade and installation of runoff retention measures

Surface water quality in the UK and much of Western Europe has improved in recent decades, in response to better point source controls and the regulation of fertilizer, manure and slurry use. However, diffuse sources of pollution, such as leaching or runoff of nutrients from agricultural fields, and micro-point sources including farmyards, manure heaps and septic tank sewerage systems, particularly systems without soil adsorption beds, are now hypothesised to contribute a significant proportion of the nutrients delivered to surface watercourses. Tackling such sources in an integrated manner is vital, if improvements in freshwater quality are to continue. In this research, we consider the combined effect of constructing small field wetlands and improving a septic tank system on stream water quality within an agricultural catchment in Cumbria, UK. Water quality in the ditch-wetland system was monitored by manual sampling at fortnightly intervals (April-October 2011 and February-October 2012), with the septic tank improvement taking place in February 2012. Reductions in nutrient concentrations were observed through the catchment, by up to 60% when considering total phosphorus (TP) entering and leaving a wetland with a long residence time. Average fluxes of TP, soluble reactive phosphorus (SRP) and ammonium-N (NH4-N) at the head of the ditch system in 2011 (before septic tank improvement) compared to 2012 (after septic tank improvement) were reduced by 28%, 9% and 37% respectively. However, TP concentration data continue to show a clear dilution with increasing flow, indicating that the system remained point source dominated even after the septic tank improvement.

PRA: A Tool to Address WatSan Issues and Achieve the Standard In Low Income Settlements An empirical study on a Dhaka slum

Most of the slums in Dhaka lack in safe water supply and sanitation facilities. This study was performed in a slum situated near Mohammadpur embankment known as Shopon’s slum. Participatory rural appraisal method was used to collect information and analyze the WatSan problems of the slum. It is built on low lying marsh land and stagnant water. Water supply is illegally obtained from municipal connection and insanitary hanging latrines are used. According to the analysis lack of property rights, financing, lack of space and low elevation are the main reasons for water-sanitation problem of the slum. Resulting effects are inconvenience, long waiting time, disease outbreak, water logging etc. After considering standards set by DPHE and slum dwellers demand, a submerged septic tank system based sanitation plan and a legal water supply with storage tank and collection points for the community is proposed. PRA tools were proved to be helpful for this purpose. Vol. 6, December 2013, pp. 73-85

Do septic tank systems pose a hidden threat to water quality?

Aquatic ecosystems are being degraded by anthropogenic pollution on a global scale. Septic tank systems (STS), which are widely distributed in rural and peri‐urban areas, are one potential source of water pollution. Although generally regarded as the most efficient method for onsite treatment of domestic wastewater, we question whether current regulation and management of these systems is sufficient to guarantee that they function effectively. Here, we present watershed‐specific examples that illustrate some of the problems that arise when many years of inadequate regulation and management result in a legacy of failing STS that can become long‐term, chronic sources of nutrient pollution. Our data suggest that more accurate accounting of the location, performance, and degree of failure of STS, and more research into their impacts on water quality, would improve source attribution of pollutants within rural watersheds. This would ensure that education of homeowners, mitigation, interdisciplinary research, and technological innovation could be targeted in a cost‐effective way.

Membrane fouling characterization in membrane-based septic tank

Septic tank is a conventional on-site wastewater disposal system providing only primary treatment (settlement of solids), while offering little biological degradation. To further improve the quality of treated water, the conventional septic tank can be modified by the introduction of membrane module capable of effective rejection of suspended solids as well as associated particulate organic matter. However, membrane fouling by partially-treated water can be considered as one of the major limitations of the membrane-based septic tank (MBST) system. The present study was carried out in a pilot-scale MBST by using flat-sheet woven fiber microfiltration (WFMF) membrane modules. WFMF membrane module having 1 m2 effective filtration area was submerged in septic tank of 4 m3 working volume and operated at different fluxes to investigate the fouling frequency and effects of cleaning protocols. It was found that the physical cleaning protocol was effective in removing cake as well as partial pore blocking resistance without requiring chemical cleaning. On the other hand, after each operation cycle, the irreversible fouling of membrane increased.

Linking Microbial Community Structure to Function in Representative Simulated Systems

Pathogenic bacteria are generally studied as a single strain under ideal growing conditions, although these conditions are not the norm in the environments in which pathogens typically proliferate. In this investigation, a representative microbial community along with Escherichia coli O157:H7, a model pathogen, was studied in three environments in which such a pathogen could be found: a human colon, a septic tank, and groundwater. Each of these systems was built in the lab in order to retain the physical/chemical and microbial complexity of the environments while maintaining control of the feed into the models. The microbial community in the colon was found to have a high percentage of bacteriodetes and firmicutes, while the septic tank and groundwater systems were composed mostly of proteobacteria. The introduction of E. coli O157:H7 into the simulated systems elicited a shift in the structures and phenotypic cell characteristics of the microbial communities. The fate and transport of the microbial community with E. coli O157:H7 were found to be significantly different from those of E. coli O157:H7 studied as a single isolate, suggesting that the behavior of the organism in the environment was different from that previously conceived. The findings in this study clearly suggest that to gain insight into the fate of pathogens, cells should be grown and analyzed under conditions simulating those of the environment in which the pathogens are present.

Effectiveness of onsite wastewater reuse system in reducing bacterial contaminants measured with human-specific IMS/ATP and qPCR

Water shortages and the drive to recycle is increasing interest in reuse of reclaimed wastewater. Timely and cost-effective ways to detect fecal pollutants prior to reuse increases confidence of residents and neighbors concerned about reuse of reclaimed wastewater. The on-site wastewater treatment and reuse systems (OWTRS) used in this study include a septic tank, peat bioreactor, ClO2 disinfection and land spray irrigation system. Bacteroides fragilis, Escherichia coli and Enterococcus spp., were tested with immunomagnetic separation/ATP bioluminescence (IMS/ATP), qPCR and culture-based methods. The results displayed a 2-log reduction in fecal bacteria in the peat bioreactor and a 5-log reduction following chloride dioxide disinfection. The fecal bacteria levels measured by IMS/ATP correlated with qPCR results: HuBac 16S (R2 = 0.903), Bf-group 16S (R2 = 0.956), gyrB (R2 = 0.673), and Ent 23S (R2 = 0.724). This is the first study in which the newly developed human-specific IMS/ATP and previously developed IMS/ATP were applied for determining OWTRS efficiency. Results of the study revealed that IMS/ATP is a timely and cost-effective way to detect fecal contaminants, and results were validated with qPCR and culture based methods. The new IMS/ATP can also be applied broadly in the detection of human-originated fecal contamination.

Nutrient emissions to water from septic tank systems in rural catchments: Uncertainties and implications for policy

Septic tank systems (STS) are widely used to treat domestic wastewater from individual dwellings in rural areas but are a potential source of water pollution. However, their contribution to freshwater eutrophication and impacts on human health are uncertain and difficult to quantify. Five case studies are presented to highlight the issues underpinning this problem. Uncertainty exists over the numbers and locations of STS because registration is not fully implemented in all regions. Underestimating the numbers of STS located in a catchment can lead to overestimation of the relative contribution from diffuse sources such as agriculture. In turn, this may lead to potential delays in meeting water quality limits due to disproportionate targeting of potential sources. System performance is uncertain due to a lack of information on factors (such as siting, design, age, nature and level of maintenance, proximity to a watercourse) that affect nutrient retention rates. Many systems still discharge directly to a watercourse, or to a drainage network closely connected to a watercourse despite prohibition of such discharges. Their effect on water quality is also uncertain because current nutrient abatement policies ignore the temporal variation in nutrient loading that can influence ecological response in streams and connecting ditches. These case studies show that although STS constitute a relatively small (often l10%) portion of total annual catchment nutrient loads, they can still significantly increase in-stream nutrient concentrations, especially during low flow periods in summer. STS may therefore be a greater risk to riverine eutrophication and human health than is currently assumed. More sophisticated resolution of source apportionment is needed to fully capture water quality impairment due to clustering of STS along stream networks. Targeted surveys and public awareness campaigns are useful tools for identifying failing STS, improving STS maintenance and highlighting alternative treatment options for use in catchment areas that are especially sensitive or valuable. These case studies support the need for a risk-based policy of STS registration and regulation governing maintenance to avoid further declines in the ecosystem services our freshwaters provide.

Low flow water quality in rivers; septic tank systems and high-resolution phosphorus signals

Rural point sources of phosphorus (P), including septic tank systems, provide a small part of the overall phosphorus budget to surface waters in agricultural catchments but can have a disproportionate impact on the low flow P concentration of receiving rivers. This has particular importance as the discharges are approximately constant into receiving waters and these have restricted dilution capacity during ecologically sensitive summer periods. In this study, a number of identified high impact septic systems were replaced with modern sequential batch reactors in three rural catchments during a monitoring period of 4 years. Sub-hourly P monitoring was conducted using bankside-analysers. Results show that strategic replacement of defective septic tank systems with modern systems and polishing filters decreased the low flow P concentration of one catchment stream by 0.032 mg TP L − 1 (0.018 mg TRP L − 1 ) over the 4 years. However two of the catchment mitigation efforts were offset by continued new-builds that increased the density of septic systems from 3.4 km − 2 to 4.6 km − 2 and 13.8 km − 2 to 17.2 km − 2 and subsequently increased low flow P concentrations. Future considerations for septic system mitigation should include catchment carrying capacity as well as technology changes.

Modeling the system dynamics for nutrient removal in an innovative septic tank media filter

A next generation septic tank media filter to replace or enhance the current on-site wastewater treatment drainfields was proposed in this study. Unit operation with known treatment efficiencies, flow pattern identification, and system dynamics modeling was cohesively concatenated in order to prove the concept of a newly developed media filter. A multicompartmental model addressing system dynamics and feedbacks based on our assumed microbiological processes accounting for aerobic, anoxic, and anaerobic conditions in the media filter was constructed and calibrated with the aid of in situ measurements and the understanding of the flow patterns. Such a calibrated system dynamics model was then applied for a sensitivity analysis under changing inflow conditions based on the rates of nitrification and denitrification characterized through the field-scale testing. This advancement may contribute to design such a drainfield media filter in household septic tank systems in the future.

Methane, Carbon Dioxide, and Nitrous Oxide Emissions from Septic Tank Systems

Emissions of CH4, CO2, and N2O from conventional septic tank systems are known to occur, but there is a dearth of information as to the extent. Mass emission rates of CH4, CO2, and N2O, as measured with a modified flux chamber approach in eight septic tank systems, were determined to be 11, 33.3, and 0.005 g capita(-1) day(-1), respectively, in this research. Existing greenhouse gas (GHG) emission models based on BOD (biochemical oxygen demand) loading have estimated methane emissions to be as high as 27.1 g CH4 capita(-1) day(-1), more than twice the value measured in our study, and concluded that septic tanks are potentially significant sources of GHGs due to the large number of systems currently in use. Based on the measured CH4 emission value, a revised CH4 conversion factor of 0.22 (compared to 0.5) for use in the emissions models is suggested. Emission rates of CH4, CO2, and N2O were also determined from measurements of gas concentrations and flow rates in the septic vent system and were found to be 10.7, 335, and 0.2 g capita(-1)day(-1), respectively. The excellent agreement in the CH4 emission rates between the flux chamber and the vent values indicates the dominant CH4 source is the septic tank.