On-site Domestic Wastewater Treatment Research Articles

［Joint Seminar by Younger Researcher's Associations at JSMCWM and SECE］ Design of Onsite Domestic Wastewater Treatment Systems toward Decarbonization

［Joint Seminar by Younger Researcher's Associations at JSMCWM and SECE］ Design of Onsite Domestic Wastewater Treatment Systems toward Decarbonization

Feasibility of sequential anaerobic-aerobic integrated settler-based biofilm reactor for onsite treatment of domestic wastewater

The present study investigates the applicability of sequential anaerobic aerobic integrated settler-based biofilm reactor (SAABR) for the onsite treatment of domestic wastewater. The main aim of the study is to overcome the inherent flaws in an anaerobic system as well as enhancing the effluent quality by means of aerobic post-treatment. The sequential system consisted of an anaerobic settler is followed by two biofilters, anaerobic as well aerobic in series. The first biofilter is anaerobic and the second one is aerobic. The system was run on two hydraulic loading conditions (steady and non-steady flow) with a 24-hour hydraulic retention time (HRT) for the anaerobic system and a 2-hour HRT of aerobic filters. It was found that the performance of the system at steady flow stood at 93.9 ± 2.6, 93.3 ± 1.8, 91.2 ± 4.2, 75.8 ± 3.8 and 98.7 ± 1.1% in terms of total suspended solids (TSS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN) and faecal coliform (FC), respectively while at non-steady flow, it decreased slightly. The Field Emission Scanning Electron Microscope (FESEM) showed the presence of anaerobic bacteria in the system. The system is able to overcome the major flaws of the anaerobic systems and able to deliver high effluent quality. The study demonstrated that the sequential system can be a sustainable alternative for the onsite treatment of domestic wastewater, particularly in rural areas of the developing countries like India.

Enhanced Onsite Treatment of Domestic Wastewater Using an Integrated Settler-Based Biofilm Reactor with Efficient Biogas Generation

The growing population and increasing urbanization have led to a surge in domestic wastewater generation, posing significant challenges for effective and sustainable treatment. The present study demonstrates a novel and sustainable approach for the onsite treatment of domestic wastewater using an integrated settler-based biofilm reactor (ISBR) with efficient biogas generation. The ISBR provides an optimized environment for the growth of biofilm, facilitating the removal of organic pollutants and pathogens. Moreover, the ISBR enables the recovery of a valuable resource in the form of biogas, thus enhancing the overall utility of the treatment process. The performance of the ISBR was comprehensively evaluated at laboratory scale through treating the actual domestic wastewater generated from the hostel of Manipal University Jaipur. The ISBR system was operated under an ambient environment at a hydraulic retention time (HRT) of 24 h. The results demonstrated remarkable efficiency in terms of chemical oxygen demand (COD), total suspended solids (TSS), and coliforms removal, with average removal efficiency being more than 90%. According to the COD mass balance analysis, 48.2% of the influent COD was recovered as bioenergy. The chromatogram revealed a high percentage of methane gas in the collected biogas sample. The field emission scanning electron microscope (FESEM) analysis of the accumulated sludge in the ISBR system depicted the morphology of methanogenic bacteria. Both the experimental and theoretical results confirmed the feasibility and sustainability of the ISBR system at the onsite level.

Environmental assessment of on-site source-separated wastewater treatment and reuse systems for resource recovery in a sustainable sanitation view

Sustainable sanitation solutions are necessary for promoting public health and environmental security. In this study, on-site domestic wastewater treatment (WWT) systems used for households in rural and peri-urban areas of Brazil were compared in different scenarios from a life cycle assessment (LCA) perspective. The evaluated scenarios represented different practices in wastewater management, such as direct discharge into the soil, rudimentary treatment, septic tank, public sewerage system, and source separation of wastewater streams for water, nutrient, and organic matter recovery. The WWT technologies considered in the proposed scenarios of source-separated wastewater streams were as follows: an evapotranspiration tank (TEvap) and composting toilet for blackwater, a modified constructed wetland (EvaTAC) for greywater, and a storage tank for urine. LCA was performed in this study according to the ISO standards to assess the environmental impacts at both midpoint and endpoint levels. The results show that on-site source-separated wastewater treatment systems with resource recovery result in significant reductions in environmental impacts compared to scenarios with precarious conditions or ‘end-of-pipe’ solutions. For example, regarding the human health damage category, the scenarios involving resource recovery, including systems such as EvaTAC, TEvap, composting toilet, and urine storage tank, demonstrate significantly lower values (−0.0117 to −0.0115 DALY) compared to scenarios with rudimentary cesspits and septic tanks (0.0003 to 0.001 DALY). We conclude that the focus should be beyond mere pollution aspects and instead concentrate on the benefits of the co-products, which are: avoiding the extraction and consumption of valuable and increasingly scarce raw materials, such as potable water, and production of synthetic fertilizer. Furthermore, it is highly recommended that an LCA of sanitation systems synergistically integrates the WWT process, the constructive aspects, and the resource recovery potential.

Acceptance of on-site wastewater treatment and reuse in Bengaluru, India: The role of perceived costs, risks, and benefits

In dealing with water pollution and freshwater scarcity, on-site treatment and reuse of domestic wastewater has shown to be a promising solution. To increase on-site wastewater treatment and reuse, some cities, among them Bengaluru in India, have mandated the installation and use of the necessary technology in certain building types. However, even with a mandate, a successful and sustainable implementation of the technology, including reliable operation, monitoring, and maintenance, depends on the acceptance (i.e. positive valuation) of the technology and its use by the (prospective) users. Literature on technology acceptance indicates perceived costs, risks, and benefits of the respective technology as key predictors of acceptance. Therefore, the present online study assessed this relationship for on-site systems in Bengaluru. The relation was analysed separately for mandated users of on-site systems (N = 103) and current non-users (i.e. potential prospective users, should the mandate be expanded; N = 232), as the perceptions might differ between the two groups, due to the personal experience with the technology among users. The results show that for mandated users and non-users, acceptance of on-site systems is explained by perceived benefits only, namely a positive image of users, environmental benefits, and, only for non-users, also financial benefits for the city. The findings suggest that interventions aimed at promoting on-site systems should include emphasis on the benefits of on-site systems. Whenever possible, interventions should be tailored to the target group's individual cost, risk, and benefit perception.

Performance Evaluation of Commercial Package Systems Used in Kuwait for on-Site Treatment and Reuse of Domestic Wastewater

Kuwait’s wastewater management scheme consists of a huge centralized sewerage system that transports all wastewater generated for treatment at central municipal plants for wastewater treatment. However, there are a few remote sites that are still not connected to the public sewerage system. In such sites, on-site systems such as conventional septic tank or package systems are commonly used. This study assessed the performance of two package systems used in Kuwait for on-site wastewater treatment and reuse. Wastewater samples were collected weekly for five months from influent and effluent streams of two package systems located at Ahmedi and Kadhmah areas of Kuwait. Comparison of the means of the laboratory results to the guidelines of Kuwait Public Authority for Environment (KEPA) indicated that the effluents of the two systems are suitable to be reused as irrigation water. However, results obtained also showed that performances of both units were highly fluctuating.

Performance of the anaerobic baffled reactor for primary treatment of rural domestic wastewater in Iraq

Abstract The purpose of this work is to evaluate the performance of the anaerobic baffled reactor (ABR) for on-site primary treatment of domestic wastewater in rural areas of Iraq. The performance of the three-chamber ABR has been investigated at four different hydraulic retention times (HRTs) ranging from 6 to 36 h. The results showed that the chemical oxygen demand (COD) removal efficiency is enhanced with increasing HRT, where it was recorded at 75, 71, 63, and 56% removals rate of COD at HRTs of 36, 24, 12, and 6 h, respectively. The mean steady-state removals of total suspended solids are 91, 78, 72, and 67% at HRTs of 36, 24, 12, and 6 h, respectively. Also, it was shown that there was low-nutrients removal within the ABR. Consequently, the effluent ABR wastewater needs to be post-treated before being discharged to the receiving water bodies. In general, it is concluded that the ABR could introduce a solution for on-site primary treatment of domestic wastewater in rural communities in Iraq.

A Fixed-Film Bio-Media Process Used for Biological Nitrogen Removal from Sewage Treatment Plant

In this study, a lab-scale fixed-film bio-media process was developed and operated to evaluate nitrogen removal from domestic sewage treatment plants. For nitrogen removal, the fixed-film bio-media process was applied in series with anaerobic, anoxic, and aerobic units in three separate reactors that were operated continuously at the same loading rates and hydraulic retention time. A biofilm separation bioreactor was developed for on-site domestic wastewater treatment and the bioreactor employed synthetic fiber modules so that the biomass could be completely attached to the media. In this paper, the performance of the fixed-film bio-media process with an average flow rate was evaluated before and after stabilization of the treatment system for nitrogen removal. The results show that the fixed-film bio-media process was successful for improved nitrogen removal from secondary and tertiary treated wastewater, with a 77% decrease in the total nitrogen discharge. Rapid nitrification could be achieved, and denitrification was performed in the anoxic filter with external carbon supplements during tertiary treated sewage wastewater. However, aeration was supplied after the stabilization process to achieve the nitrification and denitrification reaction for nitrogen removal. However, stable aeration supply could enhance nitrification at moderate temperature with benefits from complete retention of nitrifying bacteria within the system due to bio-media separation.

Sludge accumulation rates in septic tanks used as part of the on-site treatment of domestic wastewater in a northern maritime temperate climate

On-site domestic wastewater treatment systems (DWTS) are used by a significant fraction of the world's population and are used by one third of the population in Ireland. The effective operation of these DWTS requires regular desludging and so knowledge of expected filling rates is essential for both the homeowner as well as the municipalities which accept this sludge in licensed premises; yet few studies have attempted to quantify the sludge accumulation in such decentralized systems. Field studies were carried out on 27 septic tanks across Ireland to quantify sludge accumulation rates from which optimum desludging frequencies for use in Ireland have then been determined. Sludge accumulation was found to be very high in the first 12 months of system operation (approximately 250 L/person/y) but dropped off to below 150 L/person/y after 2 years. Such volumetric accumulation rates appear high compared to the few other reported international studies; however, measured solids accumulation rates, were low compared to international estimates, ranging from 1 to 10 kg/person/y. An equation for optimal desludging frequencies between 3 and 5 years has been formulated for various tank sizes and occupancy based on the Irish field data and previous international research - 5 years being the maximum allowable interval between desludging before the limiting volume of 50% sludge in the tank is reached.

A Simple Method for Identifying Appropriate Areas for Onsite Wastewater Treatment

Onsite Domestic Wastewater Treatment Systems (ODWTS) are increasingly important for treating domestic wastewater in metropolitan contexts, especially in suburban sectors isolated from sewer networks and centralized treatment plants. When ODWTS are not correctly planned and located in suitable places, or are not properly designed, they can cause groundwater contamination and generate risks for human health. This work presents a Spatial Decision Support System (SDSS) to zone specific areas based on a few simple parameters. The proposed tool can be easily adapted to different contexts, even where institutional capacities are low. Results obtained in the metropolitan area of the Lerma Valley (Salta, Argentina) show strong contradictions between our zoning and current urbanization features in the study area. As a result, environmental impacts and health hazards are likely to manifest in the short or medium term. The sectors with the best receptivity conditions were found in the southern sector of the study area. We argue that ODWTS can be safely implemented in many areas as long as this concept is embedded in urban planning initiatives, which usually also require the consolidation or development of appropriate institutions and control systems.

On-site domestic wastewater treatment system using shredded waste plastic bottles as biofilter media: Pilot-scale study on effluent standards in Bhutan

In this study, a 1000 L/d capacity one-off on-site wastewater treatment system was operated for over a year as a pilot alternative to the conventional on-site treatment as currently used in urban Bhutan. An up-flow anaerobic sludge blanket (UASB) was used for blackwater treatment (to replace “septic tank followed by an anaerobic biofilter (ABF) (to replace soak pits) for the treatment of a mixture of greywater and UASB effluent. Shredded waste plastic bottles were used as the novel biofilter media in the ABF. During a yearlong operation, the pilot system produced a final treated effluent from ABF with average BOD5 28 mg/L, COD 38 mg/L, TSS 85 mg/L and 5 log units of Escherichia coli. These effluents met three out of four of the national effluent discharge limits of Bhutan, but unsuccessful to meet the Escherichia coli standard over a yearlong operation. Further, process optimisation may enable more significant Escherichia coli removal. An economic analysis indicates that the total unit cost (capital and operating expenditures) of this alternative wastewater treatment system for more than 50 users range between USD 0.27–0.37/person/month comparable to USD 0.29–0.42/person/month for the current predominant on-site system, i.e., “septic tanks”. This pilot study, therefore, indicates that this wastewater treatment system using shredded waste plastic biofilter media has high potential to replace the current conventional treatment, i.e., “septic tanks”, which are often overloaded with greywater and discharging effluents which does not meet the national standards.

Sustainable technologies for on-site domestic wastewater treatment: a review with technical approach

Sustainable technologies for on-site domestic wastewater treatment: a review with technical approach

Engineered silver nanoparticle (Ag-NP) behaviour in domestic on-site wastewater treatment plants and in sewage sludge amended-soils

Untreated sludge from small-scale on-site domestic wastewater treatment systems (septic tanks) was spiked with 20, 60 and 100 nm silver nanoparticles (Ag-NPs) to investigate Ag-NP behaviour in these systems that are widely distributed in rural areas. In addition, the release of Ag-NPs from a previously spiked clay-rich loam reference soil (LUFA 2.4) was evaluated, in the presence and absence of untreated sludge, to simulate the common practice of sludge disposal by spreading on agricultural land. Single particle ICP-MS was used to determine Ag-NP size distribution and the results were compared with total Ag (Ag-NP and ionic) measured in acid digested samples. As documented previously for large municipal scale wastewater treatment plants, Ag-NPs are found to be overwhelmingly (~98%) retained in the sludge in these small-scale systems. The Ag-NP retention efficiency on the LUFA reference soil amended with sludge is approximately 10 times greater than that of LUFA soil alone (in the absence of sludge). For soil spiked with 60 nm Ag-NPs, the calculated average diameter of Ag-NPs in the supernatant, after 24 h was 45 ± 3 nm (dissolution rate 7.2E−06 mol/m2·h for 60 nm Ag-NP), smaller than that of supernatant from the combined sludge/soil system (52 ± 2 nm), indicating lower Ag-NP dissolution rates in the sludge-amended soil. This study provides new information about the leachability of Ag-NPs from septic tank sludge and suggests that the effluent and sludge from septic tanks are potential sources of both nano- and dissolved ionic-Ag to environmental waters.

Developing of Performance Testing Scheme for Decentralized Domestic Wastewater Treatment Plant in Indonesia

Most of the urban and rural areas in Indonesia still use individual scale of decentralized on-site domestic wastewater treatment such as pit latrines and septic tank. For some building and small community using communal scale of wastewater treatment plant such as fabricated biofilter tank, UASB (up-flow anaerobic sludge blanket), Rotating Biological Contactor (RBC) and wetland. Many application of the decentralized Wastewater Treatment Plants (WWTP) have low performance and the effluent does not meet standard effluent. To ensure the compliance to the regulation, it is necessary to develop the performance testing scheme for decentralized domestic wastewater treatment plant. The objective of the study is to review performance testing scheme in Indonesia, include the legal aspects, existing performance testing procedure for inspection and certification. The target is to develop performance testing schemes consists of testing standard and institutions scheme. The methodology of research are primary and secondary data collection done through field observation and discussion in stakeholder meeting with stakeholder related. The data analysis of this study are comparative study of certification system of decentralized WWTP in Japan, Thailand and Indonesia, descriptive analysis of performance testing method and the role of stakeholders. In conclusion Indonesia has not have regulation regarding certification schemes for decentralized WWTP. The certification schemes is needed to guarantee the WWTP product compliance with the performance standard and effluent standard. The developing decentralized WWTP need the regulation regarding testing body, the provision of performance testing standard, competent testing body, equipment and human resources.

Using coconut husks in a full-scale decentralized wastewater treatment system: The influence of an anaerobic filter on maintenance and operational conditions of a sand filter

The critical situation of domestic wastewater treatment in the rural areas of Brazil stimulates the development or improvement of on-site systems using cheap and sustainable materials that can be applied in small and isolated communities. Although this is an important theme, few real scale systems have been studied. This study investigated a full-scale on-site domestic wastewater treatment system composed of a septic tank, an anaerobic filter filled with green coconut husks (Cocos nucifera) and an intermittent sand filter. The experiment was conducted in a rural area located in the city of Campinas (Brazil) and the system was built to serve a small community. The quality of the effluent generated by this combination is in accordance with Brazilian and European legislation and even allows for its reuse in agricultural activities. The results also demonstrate the feasibility of using coconut husks in anaerobic filters, providing a new and more sustainable destination for this material, which is normally treated as solid waste. The combination was shown to be a viable technology for small communities.

Kinetics of nutrient removal in an on-site domestic wastewater treatment facility

Domestic wastewater from office building has not been maintained well especially in the areas where the sewerage system is unavailable. The aims of this research were to investigate the performance and kinetics of nutrient removal in an on-site domestic wastewater treatment facility which consists of anaerobic and aerobic systems for treating wastewater from office building. The experimental data obtained from the variations of COD:N:P ratio 250:28:2.5, 350:38:2.9, 450:47:3.3, and 600:60:3.7 with three different HRT 48h, 24h, and 12h. A One-way ANOVA was performed to investigate the effects of HRT and initial concentration of TN and TP on the performance of nutrient removal. In order to obtain the kinetic coefficients, First Order, Second Order and Stover-Kincannon Models were employed. The results showed that maximum TN and TP removal efficiency were 56% and 86%, respectively. The results of one-way ANOVA showed that HRT and initial concentration of TN and TP gave the significant effects on nutrient removal (p < 0.05). Second Order and Stover-Kincannon Models were found to be more appropriate models for prediction of TN removal in this facility. Controlling HRT and C: N: P ratio may keep good performance of nutrient removal in this facility.

Suitability of fluorescent whitening compounds (FWCs) as indicators of human faecal contamination from septic tanks in rural catchments

Rural river catchments are impacted by diffuse pollution sources from agricultural practices and on-site domestic wastewater treatment systems (DWWTS), mainly septic tanks. Methods that can distinguish between contamination sources will significantly increase water management efficiency as they will allow for the development and application of targeted remediation measures. Fluorescent whitening compounds (FWC), are used as optical brighteners in laundry detergents and enter the environment through the discharge of domestic wastewater effluents. Due to their human specific source and potential simple fluorometric measurement this represents a very attractive method to be used by state monitoring agencies.In this study the suitability of FWCs as chemical indicators for human faecal contamination has been investigated in rural Irish catchments. It was found that no quantitative measurements are possible for FWCs in natural waters when using simple fluorometric methods. Hence a simple presence/absence approach needs to be applied. The detectability of FWCs was quantified and found to decrease with higher organic matter content of the river water which has its own fluorescence. This enabled the establishment of equations to predict detection limits and assess the method's suitability for individual catchments based on organic matter concentrations. Furthermore a modified photodecay method is suggested that increases sensitivity of the technique by up to 59%. Applications at rural study sites found some removal of FWCs in percolation areas of DWWTSs but they were still detectable 40 cm below the infiltration depth. FWCs were also detected as distinguishable peaks in impacted streams where septic tank effluents have a high contribution to the river flow.

Performance evaluation of package plant for treatment of single household domestic wastewater

This study was carried out to evaluate the performance of an anaerobic packaged onsite system as an alternative to septic tank for the rural and semi-urban areas of developing countries where centralized sewerage facilities are not available. Potential application was identified on the basis of pollutant removal efficiency. The average per-capita wastewater generation was found to be 140 L/person/day with maximum contribution from the kitchen. The average removal efficiency of the system for chemical oxygen demand (COD), biochemical oxygen demand, total suspended solids, total nitrogen, total phosphate and fecal coliform was 70.9 ± 11.8%, 68.7 ± 8.5%, 78.1 ± 4.7%, 20.2 ± 8.4%, 13.8 ± 3.7% and 86.5 ± 1.6%, respectively. Despite a satisfactory performance, the anaerobically-treated effluent did not meet the disposal standards and required subsequent post treatment. An electrochemical reactor with aluminium electrodes, at a potential difference of 12 V, showed appreciable potential for use in actual households as a post treatment option for further removal of the pathogens and COD. The treated domestic wastewater, with electrocoagulation as a post-treatment measure, was successfully reused for non-potable purposes. Therefore, the package system, in conjugation with electrocoagulation process, promises to be a highly efficient technology for the onsite treatment of domestic wastewater in developing countries while facilitating reuse of the treated effluent for various recreational purposes as well as a safe discharge.

Performance evaluation of a single household anaerobic packaged system for onsite domestic wastewater treatment

The present study evaluated the performance of a uniquely configured compact anaerobic packaged system as an alternative to the conventional septic tank for a single household. The system consisted of two bioreactors, a septic tank followed by an upflow anaerobic filter. Both reactors were accommodated within a single compact unit. The treatment efficiency of the system was identified on the basis of its pollutant removal efficiency and desludging interval over a period of 12 months. The system was fed with actual onsite wastewater with large fluctuations in the flow throughout a day. The average removal efficiency for COD, BOD, TOC, TSS and faecal coliform was observed as 70.9, 68.7, 62.1, 78.1 and 86.5% (1.1 log), respectively. A hydrodynamic study revealed a low dead volume (19.8%) with plug flow regime within the system. Based on a significantly better performance than the septic tank, the present system has a good potential for application in the unsewered rural and peri-urban areas of the developing countries like India.

Soil infiltration bioreactor incorporated with pyrite-based (mixotrophic) denitrification for domestic wastewater treatment

In this study, an integrated two-stage soil infiltration bioreactor incorporated with pyrite-based (mixotrophic) denitrification (SIBPD) was designed for domestic wastewater treatment. Benefited from excellent adsorption ability and water-permeability, soil infiltration could avoid clogging, shorten operating time and lower maintenance cost. Respiration and nitrification were mostly engaged in aerobic stage (AES), while nitrate was majorly removed by pyrite-based mixotrophic denitrification mainly occurred in anaerobic stage (ANS). Fed with synthetic and real wastewater for 120days at 1.5h HRT, SIBPD demonstrated good removal performance showing 87.14% for COD, 92.84% for NH4+-N and 82.58% for TP along with 80.72% of nitrate removed by ANS. TN removal efficiency was 83.74% when conducting real wastewater. Compared with sulfur-based process, the effluent pH of SIBPD was maintained at 6.99–7.34 and the highest SO42− concentration was only 64.63mgL−1. This study revealed a promising and feasible application prospect for on-site domestic wastewater treatment.