Domestic Wastewater Treatment Systems Research Articles

Development of a Self-Contained, PV-Powered Domestic Toilet and Wastewater Treatment System

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Public awareness, behaviours and attitudes towards domestic wastewater treatment systems in the Republic of Ireland

Summary Numerous studies have highlighted and quantified the role of domestic wastewater treatment systems (DWWTSs) as significant sources of human-specific aquatic contaminants in both developed and developing regions, particularly with respect to private and municipal groundwater supplies. However, from a socio-hydrological perspective, little work has focused on these systems and the potential environmental and human burden posed. This is of particular relevance in the Republic of Ireland, where approximately one third of the population is serviced by DWWTSs. The objective of the current study was to examine levels of awareness and subsequent behavioural tendencies among owners and users of DWWTSs in the Republic of Ireland, particularly in light of recent and future (national and EU) legislative amendments. Structured questionnaires were completed bi-modally with 1106 Irish respondents. Analysis identified a number of significant knowledge gaps which currently exist among DWWTS users in Ireland. These were associated with environmentally inadvisable behavioural practises, potentially leading to increased contamination vulnerability and subsequently, increased human exposure to waterborne contaminants. Household water supply type was significantly associated with DWWTS threat acknowledgement (p = 0.014), with unregulated private groundwater users exhibited the lowest awareness of DWWTS as a potential source of aquatic contaminants despite being the group at greatest risk. A bi-modal clustering approach was employed, with respondents found to fall into one of three distinct “attitudinal” clusters. Future engagement strategies should strive to provide guidance regarding the role of people and their activities within the hydrological cycle. The current study reinforces this conclusion, while providing evidence-based recommendations regarding provision of demographically focused educational strategies; these will further increase environmental policy compliance, and in so doing, decrease the human health and environmental contamination burden posed by DWWTSs.

Performance of wetland roof with Melampodium paludosum treating septic tank effluent

Wetland roof (WR) system was developed to apply for building terrace and top roof in the urbanized area of Ho Chi Minh City. This study aims to improve the green area of the city and to treat domestic wastewater through a shallow horizontal subsurface constructed wetland that is located in a household roof. The pilot-scale unit of horizontal subsurface flow WR system with Melampodium paludosum, an indigenous emerging plant in Vietnam, was experimented at the average hydraulic loading rate (HLR) of 338 m3/ha d (∼36 kg COD/ha d) corresponding to HRT of 18 h. The treatment performance was not significantly different for rainy and sunny days at various HLRs. It was observed that the average removal efficiency of COD was 77–78% or 20–28 kgCOD/ha d for both sunny and rainy days. It is apparent that nutrient removal was greatly achieved as indicated by TN removal efficiency of 88–91% or 17–20 kg TN/ha d. In addition, TP removal reached 72–78% or 1.6 kg TP/ha d for different HLRs. The treated effluent could comply with the standard limits of Vietnam national technical regulation for domestic wastewater. It was also observed that the growth rate of M. paludosum was 0.1 cm/day in length. The ratio between nitrogen uptake by plants over nitrogen removed by WR was 0.13, while the higher ratio of 0.68 was obtained for the case of phosphorus. The temperature of WR units was 4 ± 1°C lower than that on concrete floor that likely help saving energy for building cooling if applying WR on the top roof. Based on the experimental results obtained to date, the WR system would be a promising system for domestic wastewater treatment especially for urbanized city, where green area is of high demand.

Net energy production and emissions mitigation of domestic wastewater treatment system: A comparison of different biogas–sludge use alternatives

Wastewater treatment systems are increasingly designed for the recovery of valuable chemicals and energy in addition to waste stream disposal. Herein, the life-cycle energy production and emissions mitigation of a typical domestic wastewater treatment system were assessed, in which different combinations of biogas use and sludge processing lines for industrial or household applications were considered. The results suggested that the reuse of biogas and sludge was so important in the system's overall energy balance and environmental performance that it may offset the cost in the plant's installation and operation. Combined heat and power and household utilization were two prior options for net energy production, provided an ideal power conversion efficiency and biogas production. The joint application of household biogas use and sludge nutrient processing achieved both high net energy production and significant environmental remediation across all impact categories, representing the optimal tradeoff for domestic wastewater treatment.

Diagnosis of domestic wastewater sand filters

On-site domestic wastewater treatment (ODWT) systems are receiving renewed interest due to their simplicity of implementation, affordability and efficiency. The most widespread ODWT system is the sand filter with vertical drained flow (SFVDF). To optimise the design and maintenance of SFVDFs, it is important to be able to check the conformity of the installations, judge their treatment performance in service and estimate possible evolution and life expectancy. As yet, however, no methodology has been developed to perform these tasks. This paper proposes a new methodology for diagnosing SFVDF systems in service. The development of this methodology relies on the development of on-site characterisation of the filtering material based on the use of a light dynamic penetration test and image processing. From this, the paper proposes an automatic tool for detecting the presence of clogging in a filter and a methodology to estimate the hydraulic conductivity of the filtering material without destroying the filter. The global methodology for diagnosing SFVDF systems is presented and illustrated for a real case in order to demonstrate its advantages and efficiency.

Decentralized two-stage sewage treatment by chemical–biological flocculation combined with microalgae biofilm for nutrient immobilization in a roof installed parallel plate reactor

In this lab-scale study, domestic wastewater is subjected to a chemical biological adsorption (A-stage), followed by treatment in an innovative roof installed parallel plate microalgae biofilm reactor for nutrient immobilization (I-stage). The A-stage process was operated at a hydraulic retention time (HRT) of 1h and a solid retention time of 1day (FeSO4 as flocculant). The I-stage, which consequently received the effluent of the A-stage process, was operated at an HRT of 1day and exposed to natural light. The overall system removed on average 74% of the total chemical oxygen demand, 82% of the total suspended solids, 67% of the total nitrogen and 96% of the total phosphorous in the wastewater. The design involves a relatively low capital and operating cost which is in the order of 0.5€/m3 wastewater treated. These aspects suggest that the A/I process can be used as a decentralized domestic wastewater treatment system.

Constructed Wetland in a Compact Rural Domestic Wastewater Treatment System for Nutrient Removal

Abstract Direct discharge of scattered rural sewage into surface water bodies with no efficient and economic treatment processes is one of the main reasons for the deteriorative aquatic environment in China. In this study, a simplified pilot-scale rural wastewater treatment system has been proposed. The system consisted of an anaerobic digestion tank (for organic substances pretreatment), an aerobic five-cell submerged biofilm reactor (for organic substances degradation), and a constructed wetland (CW; for nutrients removal and effluent quality control) in sequence. A five-step water-dropping aeration technique was incorporated in the biofilm reactor for oxygen replenishment with one pump, the only equipment applied in the system that involved in water elevation and effectively alleviated the oxygen stress in the CW for nutrient removal improvement. Effects of economic vegetation species (water spinach vs. water bamboo), packing media (coal cinder vs. gravel), and flow patterns (submerged horizontal flow ...

Feasibility of contact aeration method for small-scale domestic wastewater treatment system in rural China

This study examines the feasibility of the contact aeration method for utilisation in small-scale domestic wastewater treatment facilities in various rural areas of China, where the national government starts to address the water pollution issue. Three pilot facilities using the contact aeration method with different capacities were constructed, operated and monitored in Chongqing city and Jiangsu province. In order to evaluate the feasibility of the constructed facilities, the quality of treated wastewater and the operational cost were monitored. Results obtained from the monitoring showed that BOD and COD effluent concentrations achieved quality targets in all facilities. As for the other pollutants, quality targets were met for most of the period. Operational costs of facilities bettered those set for the facility in the town of Baiyang and new village of Zhaojia, but exceeded them for the facility in the village of Dongbei. The main reasons for the differences were the electricity billing system and operational system for each facility. In order to promote small-scale aeration-based domestic wastewater treatment plants in rural China in the future, the issue of what constitutes efficient facility maintenance first needs to be addressed.

Anaerobic Membrane Bioreactors for Sustainable Wastewater Treatment

Sustainable water management is increasingly important for utilities and is driving efforts to reduce energy consumption and residuals production in domestic wastewater (DWW) treatment without compromising effluent quality. Anaerobic membrane bioreactors (AnMBRs) combine anaerobic biological treatment and membrane separation in a single process. The potential benefits of DWW treatment by AnMBRs are substantial: ♦They generate a fraction of the residuals and consume substantially less energy compared to conventional DWW treatment systems. ♦They allow for the recovery of methane, a renewable energy source, which further improves the energy balance. ♦They can be integrated in centralized or decentralized wastewater treatment schemes due to easy scalability. This title belongs to WERF Research Report Series . In short, DWW treatment using AnMBR technology potentially represents a more sustainable DWW treatment paradigm. This study addressed the following questions that highlight the challenges associated with DWW treatment with AnMBR: Can AnMBRs be operated at the low DWW temperatures experienced in many regions in the U.S. and around the world? Can AnMBR treatment meet U.S. EPA's standards for secondary treatment? Can methane be recovered efficiently during low-temperature AnMBR treatment of DWW? ISBN: 9781780400532 (eBook)

Electricity generation and microbial community in a submerged-exchangeable microbial fuel cell system for low-strength domestic wastewater treatment

A submerged type microbial fuel cell (MFC) system, which consisted of six readily exchangeable air–cathode MFCs, was evaluated for continuous treatment of low-strength domestic wastewater. When supplied with synthetic wastewater (COD 100mg/L), the system showed increasing maximum power densities from 191 to 754mW/m2 as COD loading rates increased (0.20–0.40kg/m3/day). COD removal efficiencies decreased with increased COD loading rates but the effluent COD concentrations met the relevant effluent quality standard (CODMn 20mg/L) at all conditions. The system was then operated with domestic wastewater (c.a. 100mg COD/L) at 0.32 and 0.43kg/m3/day. The system showed much lower power densities (116–149mW/m2) at both loading rates, compared to synthetic wastewater. Anodic microbial communities were completely different when the wastewater type was changed. These results suggest that the newly developed MFC system could be applied to treat low-strength domestic wastewater without requiring any additional organic removal stage.

A novel microbial fuel cell and photobioreactor system for continuous domestic wastewater treatment and bioelectricity generation

A system containing a sequential anode-cathode configuration microbial fuel cell and a photobioreactor was developed for continuous treatment of wastewater and electricity generation. Wastewater was treated by the fuel cell to decrease the chemical oxygen demand (COD), phosphorus and nitrogen and to produce electricity. The effluent from the cathode compartment of the cell was continuously fed to an external photobioreactor to remove the remaining P and N using microalgae. Alone, the fuel cell generated a maximum power of 20.3 W/m(3) and achieved removal of 85 % COD, 58 % total phosphorus (TP) and 91 % NH(4) (+)-N. When coupled with the photobioreactor, the system removed 92 % TP and 99 % NH(4) (+)-N. These results demonstrate both the effectiveness and the potential application of the coupled system to continuously treat domestic wastewater and simultaneously generate electricity.

Chemical Oxygen Demand Fractionation and Kinetic Parameters for Sequencing Batch Reactors Treating Paper Mill Wastewater

Abstract Reported data on the chemical oxygen demand (COD) fractions and kinetic parameters for the pulp and paper mill wastewater are scarce. The present study evaluates the treatability of a paper mill effluent using a laboratory scale sequencing batch reactor. Kinetic parameters associated with carbon and nitrogen removal were determined experimentally, and the activated sludge model (ASM) was used to estimate the COD fractions of the paper mill wastewater and to assess the model sensitivity to kinetic parameters. Experimental tests demonstrated removal efficiencies reaching 92.9%, 88.5%, 91.5%, and 96.4% for COD, biological oxygen demand (BOD5), total suspended solids (TSS), and total nitrogen (Total N), respectively. Incorporating anoxic sequences and operating at 35°C improved total N and phenol removal efficiencies. Few kinetic parameters were found to be similar to those reported for domestic wastewater treatment systems. Based on ASM1 simulations, the COD fractions were estimated at 0.33, 0.28, 0...

Abundance of ammonia-oxidizing bacteria and archaea in industrial and domestic wastewater treatment systems

Nitrification plays a significant role in the global nitrogen cycle. Ammonia oxidation, the first step of nitrification, is performed in wastewater treatment by both ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). Most previous studies focused on their distribution in natural environments. In this study we qualified and quantified AOB, AOA, total bacteria, and total archaea in six different wastewater treatment systems (WTSs) using clone library and real-time PCR techniques. The results revealed that wastewater quality was an essential factor for the distribution of AOB and AOA in aerobic reactors. Although both AOB and AOA were present in all samples and contributed to nitrification simultaneously, AOB were the dominant nitrifiers in the three industrial WTSs, whereas AOA were dominant in the three domestic WTSs. This indicates AOA may be more sensitive to some toxic compounds than AOB. In addition, the dominant groups of AOB in the industrial WTSs were Nitrosomonas and Nitrosospira; the composition of AOA in the domestic WTSs was very similar, possibly due to the same source of raw sewage.

The application of A/O-MBR system for domestic wastewater treatment in Hanoi

The study aims to investigate an appropriate wastewater treatment process to treat domestic wastewater in Hanoi City which contain low-strength for COD (120-200 mg/L) but high in nitrogen content (10-40 mg/L). A lab scale anoxic-oxic system with a hollow fiber-Membrane Separation Bioreactor was operated at a flow rate of 5-10 L/h over a period of 150 days. The reactor was operated at different sludge recirculation rates. The MBR maintained relatively constant transmembrane pressure. During 150 days of reactor operation, treated water quality have COD of around 20 mg/L, NH4-N of less than 1 mg/L, NO3-N of less than 5 mg/L. The system shows good and stable efficiency for organic matter and nitrogen removal without adding an external carbon source and coagulants. The results based on the study indicated that the proposed process configuration has potential to treat the low-strength wastewater in Hanoi.
 Mục tiêu của nghiên cứu là đềxuất được một công nghệhiệu quảvà phù hợp đểxửlý nước thải sinh họat ởcác đô thịcủaViệt nam, là loại nước thải được thu gom từhệthốngthoát nước chung có nồng độchất hữu cơ thấp (COD 120-200 mg/l) nhưng hàm lượng chất dinh dưỡng như Nitơ, Phốt pho khá cao (T-N:10-40 mg/L). Chúng tôi đã nghiên cứu và vận hành chạy thửmô hình xửlý sinh học yếm khí-kỵkhí (AO) kết hợp với màng vi lọc ởquy mô mô hình phòng thí nghiệm (công suất 5-10 L/h) ởcác chếđộcông suất bùn tuần hoàn khác nhau. Kết quảxửlý trong thời gian 5tháng vận hành mô hình cho thấy chất lượng nước thải sau xửlý có hàm lượng COD nhỏhơn 20 mg/L, NH4-N nhỏhơn 1 mg/L, NO3-N nhỏhơn 5 mg/L. Hiệu suất xửlý chất hữu cơ và chất dinh dưỡng rất ổn định và hệthống không phải sửdụng các nguồn bổsung chất hữu cơ hay các hóa chất trợlắng như các công nghệđang áp dụng. Kết quảcho thấy công nghệAO kết hợp màng vi lọc có khảnăng áp dụng thực tế,phù hợp với những nơi có quỹđất nhỏ, chất lượng nước sau xửlý rất cao có thểphục vụcho mục đích tái sửdụng.

UNIT-UNIT PEMROSES PENGOLAHAN LIMBAH CAIR DOMESTIK SKALA RUMAH TANGGA

In the last ten years water pollution problem in Jakarta has been becoming more serious. The highly increasing population causes the rising amount of domestic wastewater. Rivers in Jakarta have already been polluted by various wastewaters, such as from industries, domestic and many institutionals (offices, hospitals, markets/shop areas, etc.). It has been well known that the domestic wastewater contributes 70% in causing the river pollution, especially in Jakarta. Therefore it is very important to apply the proper domestic wastewater treatment system which is able to reduce thecontaminants until an environmentally required standard. Some types of domestic wastewater treatment have already been used, but the results do not fulfil the environmental required standard. At least a unit of domestic wastewater treatment should have a control tank as the beginning filter, anaerobic part, aerobic part and a sedimentation tank as the final part of the whole system. An advanced technology using a biofilter media has been proposed and based on the experiment, the result has proven that it can reduce BOD from more than 1,000 ppm to less than 30 ppm. The retention time is about 3 days. The conclusion shows that this new wastewatertreatment system is properly suitable alternative to be applied in domestic area, especially in a densely populated region. By applying the system we can also cope with the water pollution problem caused by domestic wastewater.

Experimental Validation of an Method for In Situ Estimation of Hydraulic Conductivity of Water Treatment Granular Materials

Domestic wastewater-treatment system is today a widely held technique. In order to evaluate the efficiency of these systems, it is necessary to determinate the in situ hydraulic conductivity of the water-treatment granular materials constituting them. The in situ measurement of the hydraulic conductivity of soils has proven to be imprecise, take a long time. Empirical equations based on the physical properties of soil have been proposed to overcome these difficulties. In this context, the originality of this paper is to propose an in situ method to obtain reliable input parameters for the predictive equations of Chapuis (Can Geotech J 41(5): 787–795, 2004) and Carrier (J Geotech Geoenviron Eng 129(11): 1054–1056, 2003) by using both a penetrometer and a geoendoscope. This method is described in the first part of this paper. Then, the validation of the method based on laboratory tests performed under controlled conditions for three kinds of soils is presented. Hydraulic conductivity obtained when applying the method is compared to that measured by a Darcy permeameter. The difference between these two hydraulic conductivities is less than 25%. Finally, the precision of the results is discussed.

An integrated UASB-sludge digester system for raw domestic wastewater treatment in temperate climates

To improve the performance of an upflow anaerobic sludge blanket (UASB) reactor treating raw domestic wastewater under temperate climates conditions, the addition of a sludge digester to the process was investigated. With the decrease in temperature, the COD removal decreased from 78% at 28°C to 42% at 10°C for the UASB reactor operating alone at a hydraulic retention time of 6h. The decrease was attributed to low hydrolytic activity at lower temperatures that reduced suspended matter degradation and resulted in solids accumulation in the top of the sludge blanket. Solids removed from the upper part of the UASB sludge were treated in an anaerobic digester. Based on sludge degradation kinetics at 30°C, a digester of 0.66l per liter of UASB reactor was design operating at a 3.20days retention time. Methane produced by the sludge digester is sufficient to maintain the temperature at 30°C.

Modification of DHS Bioreactor Module with Oil Palm Fiber Material for Treating Domestic Wastewater

An oil palm fiber module has been developed to modify a down-flow hanging sponge (DHS) reactor module. The objective of the proposed system is to improve two existing DHS variants of post-treatment unit for UASB treating domestic wastewater, i.e. cube-type and curtain-type sponge as domestic wastewater treatment system for developing countries. This paper describes the potential of oil palm fiber-based DHS (PF-DHS) configuration for sewage treatment. Feasibility of the PF-DHS reactor was evaluated by conducting a six-month continuous operation using actual sewage as feed. The system has been verified to have an excellent organic removal performance achieving 67% of unfiltered COD removal, and nearly perfect SS removal at the HRT of 2 h. It was observed that the organic removal rate was approximately 2.64 kg COD/m3 per day. The result recommended that the proposed PF-DHS reactor would be a promising system to alter sponge-based DHS for domestic wastewater treatment system in developing countries.

Factors affecting the performance and risks to human health of on-site wastewater treatment systems

Aerobic wastewater treatment systems (aerobic systems) are the preferred choice in a region overlying a karstic aquifer used for drinking water supplies, as they are thought to provide better protection to groundwater and human health than standard septic systems. However, aerobic systems in operation do not always perform to design standard; while this is often blamed on lack of maintenance, few studies have investigated the link directly. This study investigates the performance of domestic on-site wastewater treatment systems in South Australia, and compares effluent quality to maintenance records. Effluent from 29 septic tanks and 31 aerobic systems was analysed for nutrients, physico-chemical parameters and microbiological indicators. Aerobic systems generally provided greater treatment than septic tanks, yet most aerobic systems did not meet regulatory guidelines with high levels of indicator bacteria in 71% of samples. The effect of system size, number of household occupants and maintenance on aerobic system treatment performance was analysed: chlorine levels were positively correlated with time of last service, and nutrient concentrations were positively correlated with the number of occupants. A microbial risk assessment revealed the observed irrigation practices to be high risk; and sufficient residence time in the aquifer cannot be guaranteed for protection of groundwater used for drinking. Additional preventive measures such as irrigation management or post treatment of drinking water supply (such as UV disinfection) are required to meet public health targets.

Optimization of phosphorus removal in uniFed SBR system for domestic wastewater treatment

The characteristic of phosphorus removal and appropriate change of the traditional operation modes were investigated in UniFed sequencing batch reactor (SBR) laboratory-scale apparatus (40 L), treating actual domestic wastewater with low ratios of C/N (2.57) and C/P (30.18), providing theoretical basis for actual application of wastewater treatment plant. UniFed SBR system with its unique operation mode had the distinct superiority of phosphorus removal. On this occasion, the effect of volumetric exchange ratio (VER) and the method of influent introduction for phosphorus removal were studied. When the carbon source became the limiting factor to phosphorus release, the higher the VER, the lower the phosphorus concentration in the effluent. Three different influent patterns, including one-time filling, four-time filling, and continuous filling with the same quantity of wastewater could increase the release rate of anaerobic phosphorus from 0.082 to 0.143 mg·P·(L·min)−1. Appropriate change of the traditional operation modes could optimize the efficiency of phosphorus removal. When the feed/ decant time was extended from 2 h to 4 h, the phosphorous removal efficiency increased from 59.93% to 88.45% without any external carbon source. In the mode of alternation of anoxic-aerobic (A/O) condition, phosphorous removal efficiency increased from 55.07% to 72.27% clearly. The carbon source in the influent can be used adequately, and denitrifying phosphorus removal was carried out in anoxic stage 2 (A2). This mode was optimal for the treatment of actual domestic wastewater with low C/N and C/P ratios.