Decentralized Wastewater Treatment Research Articles

The potential of sweeping gas membrane distillation integrated with multistage bubble column dehumidifier in recovering potable water from wastewater contaminated with industrial metalworking fluids

Wastewater treatment is essential as freshwater becomes scarce due to increasing industrialization. However, the current centralized wastewater treatment technologies are suitable for large-scale applications. There is a pressing need to develop small-scale decentralized wastewater treatment techniques. Towards this goal, a new sweeping gas membrane distillation system (SGMD) integrated with a multistage bubble column dehumidifier (BCD) was designed, built and tested to treat metalworking fluid (MWF)-contaminated wastewater. The performance of the SGMD-BCD system was first optimized using deionized water experiments. The results showed that feed water temperature significantly affected permeate flux, while air and feed water mass flow rates of 10kg/hr and 90kg/hr were identified as optimum since permeate flux and gain output ratio were insignificant above these flow rates. The simulation results of the developed system-scale mathematical model revealed that multi-staging is a more preferable option for improving effectiveness compared to increasing the condensing area in a single-stage BCD. Additionally, in long-term experiments, about 35.5% and 47.7% drops in permeate flux were observed when the MWF concentration in wastewater increased from 5 to 25 wt% at feed water temperatures of 70°C and 80°C, respectively.

Lesson Learned from Yangon to Mandalay on Wastewater Treatment Systems

This paper presents a comparative analysis of wastewater management practices in Myanmar’s major cities, Yangon and Mandalay, with a focus on drawing valuable lessons from Yangon’s experiences and proposing recommendations for the improvement of Mandalay’s domestic wastewater management, drawing insights from a SWOT analysis. Both cities are facing challenges due to rapid urbanization, leading to untreated discharge into the environment. The study identifies common challenges in both Yangon and Mandalay, such as limited treatment capacity, environmental concerns, and funding gaps. The decentralized-centralized strategy is a successful approach for Yangon even though the capacity is not high. Results showed that 17.5% of Decentralized Wastewater Treatment Systems (DEWATS) users were highly satisfied and 45% were somewhat satisfied. Yangon’s experience with centralized systems showed that it took several years to cover the entire city for treatment, resulting in issues to cover revenue expenditures. If Mandalay adopts a similar, it will likely encounter the same issues. A recommended approach would be to implement an integrated system with DEWATS, which offers a better solution. The recommendations for sustainable wastewater management in Mandalay include active stakeholders’ involvement in decision-making, promoting community participation, and providing training. Transparency and shared responsibility are crucial for success. Addressing membrane fouling, sludge disposal, and implementing monthly fees are essential for sustainable implementation. An integrated approach along with environmental and social impact assessments are necessary to develop a cost-effective and efficient wastewater treatment system while safeguarding public health and the environment. These insights offer broader implications, guiding developing countries towards more effective and environmentally responsible wastewater management practices.

Effect of mechanical scouring on fouling control in greywater filtration with fluidized bed submerged membrane reactor for decentralized wastewater treatment process

Synthetic greywater was applied into a novel, fluidized submerged membrane reactor (FSMR) to compare membrane fouling with three different types of scouring agents: granular activated carbon (GAC), tubular polyvinylidene fluoride (PVDF) media, and spherical polyethylene terephthalate (PET) beads. Trans-membrane pressure (TMP) was investigated to estimate the extent to the fouling in the FSMR operated at 13 and 40 L/m2.h of permeate flux. The selection of scouring agents affected transient behavior of TMP value significantly to reduce membrane fouling. Fluidization of spherical PET beads driven by recirculating bulk suspension only through the FSMR was a prominent way to mitigate fouling. However, the cake layer was formed on membrane surface extensively as GAC or tubular PVDF media was fluidized over the course of reactor operation. At 13 L/m2.h, the TMP reached 0.74, 0.7, and 0.04 bar after 7 d operation with FSMR added with GAC particles, tubular PVDF media, and spherical PET beads as scouring agent, respectively. For the non-adsorbing PET beads, organic compound such as humic acids and proteins were a main organic fraction in cake layer. The organic removal efficiency was enhanced by complex formation resulting from the concentrated greywater in the reactor operated during extended filtration time. However, small carbon particles produced by the pulverization of GAC particles in the FSMR system disrupted fouling control and led rapid TMP rise.

Microbial denitrification characteristics of typical decentralized wastewater treatment processes based on 16S rRNA sequencing.

Despite the widespread application of decentralized wastewater treatment (WWT) facilities in China, relatively few research has used the multi-media biological filter (MMBF) facilities to investigate the microorganism characteristics. This study utilizes 16S rRNA high-throughput sequencing (HTS) technology to examine the microbial biodiversity of a representative wastewater treatment (WWT) system in an expressway service area. The pathways of nitrogen removal along the treatment route were analyzed in conjunction with water quality monitoring. The distribution and composition of microbial flora in the samples were examined, and the dominant flora were identified using LEfSe analysis. The FAPROTAX methodology was employed to investigate the relative abundance of genes associated with the nitrogen cycle and to discern the presence of functional genes involved in nitrogen metabolism. On average, the method has a high level of efficiency in removing COD, TN, NH3-N, and TP from the effluent. The analysis of the microbial community identified a total of 40 phyla, 111 classes, 143 orders, 263 families, and 419 genera. The phyla that were predominantly observed include Proteobacteria, Acidobacteria, Chloroflexi, Actinobacteria, Nitrospirae, Bacteroidetes. The results show that the system has achieved high performance in nitrogen removal, the abundance of nitrification genes is significantly higher than that of other nitrogen cycle genes such as denitrification, and there are six nitrogen metabolism pathways, primarily nitrification, among which Nitrospirae and Nitrospira are the core differentiated flora that can adapt to low temperature conditions and participate in nitrification, and are the dominant nitrogen removal flora in cold regions. This work aims to comprehensively investigate the diversity and functional properties of the bacterial community in decentralized WWT processes.

Enhanced denitrification of the AO-MBBR system used for expressway service area sewage treatment: A new perspective on decentralized wastewater treatment

Decentralized wastewater treatment warrants considerable development in numerous countries and regions. Owing to the unique characteristics of high ammonia nitrogen concentrations and low carbon/nitrogen ratio, nitrogen removal is a key challenge in treating expressway service area sewage. In this study, an anoxic/oxic-moving bed biofilm reactor (A/O-MBBR) and a traditional A/O bioreactor were continuously operated for 115 days and their outcomes were compared to investigate the enhancement effect of carriers on the total nitrogen removal (TN) for expressway service area sewage. Results revealed that A/O-MBBR required lower dissolved oxygen, exhibited higher tolerance toward harsh conditions, and demonstrated better shock load resistance than traditional A/O bioreactor. The TN removal load of A/O-MBBR reached 181.5 g‧N/(m3‧d), which was 15.24% higher than that of the A/O bioreactor. Furthermore, under load shock resistance, the TN removal load of A/O-MBBR still reached 327.0 g‧N/(m3‧d), with a TN removal efficiency of above 80%. Moreover, kinetics demonstrated that the denitrification rate of the A/O-MBBR was 121.9% higher than that of the A/O bioreactor, with the anoxic tank biofilm contributing 60.9% of the total denitrification rate. Community analysis results revealed that the genera OLB8, uncultured_f_Saprospiraceae and OLB12 were the dominant in biofilm loaded on carriers, and OLB8 was the key for enhanced denitrification. FAPROTAX and PICRUSt2 analyses confirmed that more bacteria associated with nitrogen metabolism were enriched by the A/O-MBBR carriers through full denitrification metabolic pathway and dissimilatory nitrate reduction pathway. This study offers a perspective into the development of cost-effective and high-efficiency treatment solutions for expressway service area sewage.

Using walnut shells as low-cost adsorbent materials in an anaerobic filter medium of a De-centralized wastewater treatment system (DEWATS)

The flow of unprocessed sewage through municipal sewers is a great source of water contamination. This study aims to observe the pollutants removal efficiencies of walnut shells as an efficient low-cost adsorbent material compared to gravel materials as an anaerobic filter medium. Two models of the De-Centralized Wastewater Treatment System (DEWATS) were constructed. The wastewater flowing from toilets and handwashing places was connected to anaerobic filters filled with walnut shells and gravel. The efficiency of both filter media in the removal of biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total dissolved solids (TDS), nitrate (NO3), and phosphate (PO43), pH and temperature were observed at the influent of the settler tank and then at the effluent of the collection tank (CT). Temperature and pH were within the acceptable limit of wastewater discharge. The results also indicated that the walnut shells filter media was more efficient at removing organic pollutants (TSS 94%, BOD5 88%, COD 85%, Nitrate 57%, phosphate 46%, and TDS 29%) than the gravel (TSS 81%, BOD5 82%, COD 84%, Nitrate 35%, phosphate 38%, and TDS 26%) at the successive stages. The average removal efficiency of the walnut shell was 88% while in the gravel case, it was 83%. The removal efficiency of walnut shell filters was extensively better over the complete experiment compared to gravel filters for the removal of pollutants, representing the high sorption capability of the walnut shell material. The results of this study show that the walnut shells may be a very useful substitute for other conventional fillers for anaerobic treatment in the anaerobic filter of DEWATS.

Filtro empacado con residuos de lodos de Al para la eliminación de fósforo como sistema de pulimento en una planta de tratamiento de aguas residuales

Recently, using residual Aluminum sludge (Al-sludge) from drinking water treatment plants for Phosphorus removal has been assessed and it has shown to be highly efficient. However, most of the studies have been conducted using synthetic water. Only a few works have applied this method to real wastewater (WW), and none of them have been tested in continuous mode, as a polishing step, in a pilot-scale, decentralized wastewater treatment plant (WWTP). This paper aimed to evaluate the performance of an immersed filter packed with a bed of residual Al-sludge as a polishing system for Phosphorous removal, in a pilot-scale, decentralized WWTP. The study determined at laboratory-scale the capacity for Phosphorus removal through batch and continuous tests using both synthetic and real wastewater and evaluated the effect of retention time. Based on the results, an Al-sludge immersed filter (Al-sludge Filter) at pilot-scale was constructed, implemented, and evaluated as a polishing step for the effluent of a decentralized-WWTP. The results showed that during continuous testing with real WW, the Phosphorus removal capacity was 2.55 mg P-PO43-∙L-1 using a retention time of 120 min. The Al-sludge filter as a polishing system presented an average removal efficiency of 94% ± 8% and an effluent concentration of under 0.50 mg P-PO43-∙L-1 during the first 20 operational days. For the next 17 days, the system removed 85% ± 9% on average, showing an effluent concentration of under 1.0 mg P-PO43-∙L-1. From operational day 32 onwards, the removal efficiency was 63.6% ± 10.7%, with an average effluent concentration of 2.20 ± 0.39 mg P-PO43-∙L-1.

Sustainable wastewater treatment using a new combined hybrid digester – Constructed wetland system

Constructed wetlands are one of the most promising decentralised wastewater treatment technologies for single-family homes, rural or peri-urban areas as well as for low-income areas. The present work reports for the first time the combination of a new hybrid anaerobic/anoxic digester (HD) as pre-treatment for a vertical subsurface constructed wetland (VF). Part of the nitrified VF effluent was recirculated to the HD to favour the simultaneous removal of organic matter and nitrogen, intensifying both the HD denitrification and VF nitrification processes. The results indicate that HD was the main responsible for the removal of suspended solids and organic matter, which was completed in the VF up to values always below the discharge limits. Nitrate removal ranged from 64 % to 94 % and ammonium removal from 64 % to 89 %, the former occurring mainly in the HD and the latter in the VF. The combined HD-VF system achieved high overall removal efficiency, reaching 98 % TSS, 94 % COD, 97 % BOD5, 86 % NH4+-N and 43 % TIN on average. Methane emissions were lower than those reported in the literature for CWs. The VF showed no signs of clogging. The system was operated in a sustained manner during a continuous period of 266 days with an average overall surface loading rate of 43.6 g BOD5 m−2 d−1 (range of 29–83 g BOD5 m−2 d−1). The total surface area required was 1.4 m2·equivalent inhabitant−1.

Feasibility of natural wastewater treatment systems and life cycle assessment (LCA) for aquatic systems

Background: Natural wastewater treatment systems (NWTSs) in small villages are a major challenge for European water authorities. With growing social demands for environmental practices, evaluating the feasibility and environmental impact of low-cost treatment systems for small residential areas is essential. Methods: To address this challenge, this study was conducted to evaluate 10 NWTSs seasonally in rural areas of Bursa, Turkey. Authorities over the facilities permitted the examination of workable, low-cost effluent management options. Also, using Open-LCA software based on ReCiPe MidPoint (H) version 1.67, these plants’ effects on global warming, Phosphorus-depletion, human toxicity, marine eutrophication, and freshwater eutrophication were examined. Results: According to the LCA findings, Deydinler NWTS had a greater impact across all three effect areas (freshwater eutrophication, marine eutrophication, and human toxicity), ranging from 11 to 41%. Pinar and Yenice facilities, however, had 26% and 27% larger impacts in the same two impacts (marine eutrophication and human toxicity). These systems performed on average at 67%, 50%, and 58% chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) elimination, respectively. Conclusion: According to the findings, 10 NWTSs have a treatment efficiency of about 70%. NWTSs are possibilities for decentralized wastewater treatment in small residential areas that are both cost-effective and environmentally favorable. By treating organic pollution naturally, without chemicals, and with minimal energy use, they lessen their negative environmental effects. The main findings of this study will be useful for academics in determining future research areas and identifying whom they might consult to help design carbon footprint of NWTS and future carbon reduction objectives.

Modular Functionalization of Metal‐Organic Frameworks for Nitrogen Recovery from Fresh Urine**

AbstractNitrogen recovery from wastewater represents a sustainable route to recycle reactive nitrogen (Nr). It can reduce the demand of producing Nr from the energy‐extensive Haber‐Bosch process and lower the risk of causing eutrophication simultaneously. In this aspect, source‐separated fresh urine is an ideal source for nitrogen recovery given its ubiquity and high nitrogen contents. However, current techniques for nitrogen recovery from fresh urine require high energy input and are of low efficiencies because the recovery target, urea, is a challenge to separate. In this work, we developed a novel fresh urine nitrogen recovery treatment process based on modular functionalized metal–organic frameworks (MOFs). Specifically, we employed three distinct modification methods to MOF‐808 and developed robust functional materials for urea hydrolysis, ammonium adsorption, and ammonia monitoring. By integrating these functional materials into our newly developed nitrogen recovery treatment process, we achieved an average of 75 % total nitrogen reduction and 45 % nitrogen recovery with a 30‐minute treatment of synthetic fresh urine. The nitrogen recovery process developed in this work can serve as a sustainable and efficient nutrient management that is suitable for decentralized wastewater treatment. This work also provides a new perspective of implementing versatile advanced materials for water and wastewater treatment.

Modular Functionalization of Metal-Organic Frameworks for Nitrogen Recovery from Fresh Urine.

Nitrogen recovery from wastewater represents a sustainable route to recycle reactive nitrogen (Nr). It can reduce the demand of producing Nr from the energy-extensive Haber-Bosch process and lower the risk of causing eutrophication simultaneously. In this aspect, source-separated fresh urine is an ideal source for nitrogen recovery given its ubiquity and high nitrogen contents. However, current techniques for nitrogen recovery from fresh urine require high energy input and are of low efficiencies because the recovery target, urea, is a challenge to separate. In this work, we developed a novel fresh urine nitrogen recovery treatment process based on modular functionalized metal-organic frameworks (MOFs). Specifically, we employed three distinct modification methods to MOF-808 and developed robust functional materials for urea hydrolysis, ammonium adsorption, and ammonia monitoring. By integrating these functional materials into our newly developed nitrogen recovery treatment process, we achieved an average of 75 % total nitrogen reduction and 45 % nitrogen recovery with a 30-minute treatment of synthetic fresh urine. The nitrogen recovery process developed in this work can serve as a sustainable and efficient nutrient management that is suitable for decentralized wastewater treatment. This work also provides a new perspective of implementing versatile advanced materials for water and wastewater treatment.

Linking Urban Water Management, Wastewater Recycling, and Environmental Education: A Case Study on Engaging Youth in Sustainable Water Resource Management in a Public School in Casablanca City, Morocco

The management of water resources is crucial for sustainable development, necessitating innovative solutions to address the increasing demand for safe water. Alternative approaches must be adopted to effectively engage young generations in understanding the importance of water resources. This chapter reports on an experiment that aimed to promote sustainability education by linking wastewater treatment and reuse with an educational garden. In particular, an undertaking was executed to establish a decentralized wastewater treatment system wherein purified water was employed for the purpose of irrigation. The study’s primary focus is on the association between urban water management, wastewater recycling, and environmental education. The study has two distinct components. The first segment discusses three examples of projects that have employed urban wastewater treatment and reuse to generate environmental education materials using various approaches. The second component features a case study of a public high school in Casablanca, where students participated in a questionnaire and participatory workshops to design an educational garden. The study’s outcomes include a proposed educational garden design that will be presented to the relevant authorities and project partners.

Integration of TADOX® technology to improve water reuse efficiency of constructed wetland-treated water

Abstract Constructed wetland (CW) is an effective and economical decentralized wastewater treatment (DWWT) method implemented in various developing nations. Such CW-treated water may be good for meeting discharge norms but when it comes to high-end reuse, it requires polishing and integration with advanced oxidation process (AOP)-based treatment. In this pursuit, TERI (The Energy and Resources Institute) Advanced Oxidation Technology (TADOX®) may be able to polish such streams and make the CW-treated water reusable. TADOX utilizes UV-TiO2 Photocatalysis (PC) as a secondary treatment followed by nanomaterial recovery. This study aims at evaluating TADOX treatment to polish treated water from a root zone treatment (RZT) plant. Performance evaluation of the treatments is evaluated based on key parameters for treated sewage water such as chemical oxygen demand (COD), biochemical oxygen demand (BOD), suspended solids, color, pathogens (total and thermotolerant coliforms), and persistent organic pollutants (POPs) such as caffeine, acetaminophen, ibuprofen, and diclofenac.

In situ electrogenerated Cu(III) triggers hydroxyl radical production on the Cu-Sb-SnO2 electrode for highly efficient water decontamination

The electrochemical oxidation process has the unique advantage of in-situ •OH generation for deep mineralization of organic pollutants, which is expected to provide a solution for the globally decentralized wastewater treatment and reuse. However, it is still a great challenge to develop low-cost anodes with ultrahigh •OH yield and low energy consumption. Here, a low-cost and stable mixed metal oxide (MMO) anode (Cu-Sb-SnO2) developed by a simple and scalable preparation process presents extremely high organic pollutants degradation efficiency and low energy consumption. The tetracycline degradation kinetics constant of the Cu-Sb-SnO2 system (0.362 min-1) was 9 to 45 times higher than that of other prepared anodes, which is superior to the existing anodes reported so far. The experimental results and theoretical calculations indicate that the Cu-Sb-SnO2 has moderate oxygen evolution potential, larger water adsorption energy, and lower reaction energy barrier, which is conducive to selective water oxidation to generate •OH. Notably, it is systematically and comprehensively confirmed that the generation of •OH triggered by in situ electrogenerated Cu(III) increased •OH steady-state concentration by over four times. Furthermore, the doped Cu species can play a key role in promoting charge transfer as an "electronic porter" between Sn and Sb in the electrocatalytic process by adjusting the electronic structure of the Sb-SnO2 electrode. This work paves the way for the development of MMO anodes utilizing the advantage of the Cu redox shuttle.

A survey on constructed wetland publications in the past three decades.

Decentralised wastewater treatment systems, such as constructed wetlands, are becoming increasingly popular these days because they are more economical and cost-effective than conventional plants. The primary objective of this review paper is to determine the number of studies that have been conducted on constructed wetlands, specifically 'free water surface flow constructed wetlands', 'horizontal subsurface flow constructed wetlands', 'vertical subsurface flow constructed wetlands', and 'hybrid constructed wetlands'. In addition, the paper examines the status of research publications on constructed wetlands by country, author, and journal. Based on the review, it has been found that although constructed wetland technology is economical and cost-effective, it is still not among the top 10 effluent treatment methods. Compared to other constructed wetland systems, 'hybrid constructed wetlands' have received minimal attention. Based on the search results, 4639 documents published between 1989 and 2021 have been extracted from the online edition of SCI-EXPANDED, Web of Science. The documents associated with constructed wetlands are divided into eight main document types. Articles and proceedings papers are the most common document type, accounting for 93% of all publications, followed by reviews (4%), meeting abstracts (1.3%), corrections (0.56%), editorial materials (0.38%), news items (0.2%), letters (0.04%), and book reviews (0.02%).

Additional Treatment of Nitrogen and Phosphorus Using Natural Materials in Small-Scale Domestic Wastewater Treatment Unit

The conventional wastewater treatment methods only remove up to 80% of total nitrogen (N) or phosphorus (P) from wastewater, so additional facilities are needed. This article describes a newly created other wastewater treatment unit (NCU) that increases the effectiveness of P and N removal of the small-scale biological wastewater treatment plant. This work aims to evaluate the capacity of simultaneous elimination from wastewater nitrogen (NH4-N, NO3-N) and phosphorus (PO4-P) by adsorption. NCU was filled with the sorbent material zeolite (clinoptilolite) and OCS (Fe, Mn, Ca oxides coated sand). After treatment in the main plant, wastewater flows through the NCU without using electric power. A compact system consisting of a main treatment plant and the NCU worked for 4 months, as the harmonized European Standard EN 12566-7 recommended. The NCU unit reduced PO4-P, NH4-N, and NO3-N concentrations in the effluent (74–98%, 52–99%, and 50–98%, respectively). In general, the small-scale system treated wastewater did not contain more than 1 mg/L phosphorus concentration and not more than 10 mg/L nitrogen concentration. This study demonstrates that treatment in NCU is an ecological and environmentally friendly method suitable for decentralized wastewater treatment.

Gravity-driven membrane reactor for decentralized wastewater treatment: Comparison of reactor configuration and membrane module

Gravity-driven membrane (GDM) filtration is an attractive option for decentralized wastewater treatment due to lower energy consumption. However, insufficient information is available on the design factors of GDM reactor. In this study, we investigated the impacts of membrane aeration, types of membrane modules, and biocarrier deposition onto the membrane on water quality and membrane performance of GDM reactors. In detail, the membrane air diffuser located inside the granular activated carbon (GAC)-biofilm zone had benefit for mass transfer of dissolved oxygen and achieving co-existence of anoxic and aerobic conditions in the reactor, leading to higher removal efficiencies for organics (93.8–94.6 %), nitrogen (38.2–47.2 %) and phosphorus (31.9–57.7 %), compared to the air diffuser located outside the GAC zone (90.3 % for organics, 25.3 % for nitrogen and 7.0 % for phosphorus). In addition, the inside-out ceramic hollow fibre membrane showed ∼150–200 % higher fouling resistance (mainly cake resistance) due to greater biopolymer deposition compared to the outside-in polymeric hollow fibre membrane. However, for the outside-in flat sheet configuration, the ceramic and polymeric membranes showed comparable fouling resistance. The deposition of GAC particles on the membrane surface as secondary layer could improve permeate water quality, but at the expense of an increase in irremovable fouling.

A wholelife cost and carbon perspective of alternatives to septic tanks utilising nature-based solutions

Abstract Septic tank systems (STSs) are widely utilised flowsheets for decentralised wastewater treatment in the UK. With a growing consensus that STSs have a sizeable detrimental impact on the environment, there is a need for rural flowsheets with improved treatment capabilities. This study examines the lifetime cost and carbon emissions of using an enhanced septic tank nature-based solution (EST-NBS) to improve STS compared to a package treatment system (submerged aerated filter (SAF)). The wholelife cost (WLC) of the flowsheets and Scope 2 cradle-to-grave lifetime carbon emissions (LCEs) of the flowsheets were assessed. The EST-NBS flowsheets represent a lower cost improved treatment system than SAFs at population equivalents (PEs) from 5 to 1,000. An STS averages an LCE of over 4,000 kg CO2eq PE−1, with all other considered flowsheets having lower emissions. The EST-NBS flowsheets had lower carbon emissions than SAFs. Even at low populations upgrading from an STS to an EST-NBS is a competitive abatement strategy, with costs of £260 tCO2eq−1 emissions avoided, at 1,000 PE an NBS flowsheet has an abatement cost of –£17 tCO2eq−1. This shows the potential of using NBS flowsheets in rural wastewater treatment providing both a carbon and cost incentive against traditional designs.

Performance Evaluation of a Pilot-Scale Aerobic Granular Sludge Integrated with Gravity-Driven Membrane System Treating Domestic Wastewater

This study describes a novel integration of aerobic granular sludge (AGS) with a gravity-driven membrane (GDM) system at a pilot scale with a treatment capacity of approximately 150 L per day to treat raw domestic wastewater. The treatment performance and energy consumption of the AGS-GDM system were compared to the neighboring full-scale aerobic membrane bioreactor (AeMBR), treating the same wastewater at about 4000(±500) m3 per day. The AGS-GDM system demonstrated superior nutrient (nitrogen and phosphorus) removal as compared to the AeMBR. The GDM unit was continuously supplied with AGS-treated effluent. The GDM unit started with high [ >20 L per m2 per h (LMH) ] flux, which gradually declined. The flux remained quite stable after 15 days reaching 3 LMH after 35 days without any physical or chemical cleaning. Our results suggest that AGS-GDM is a viable technology for decentralized wastewater treatment and reuse in water-scarce regions. The AGS-GDM could easily replace conventional AeMBR technology in the wastewater treatment and reclamation market.

Enhancement of a Decentralized Wastewater Treatment System by Applying a Bio-tower - A Project for Improving our Environmental Footprint

To investigate if decentralized wastewater treatment systems impact on the environment performance can be improved, a Field Bio-tower Tank Septic system was designed, installed on an existing 1,500-gal (5678 l) decentralized wastewater treatment system. The system was started up during a 14-day start-up phase, followed by a 130-day test phase. The system was operated at an average hydraulic retention time of 16.7 days based on a 90 gal (204.4 l) daily influent wastewater flow.
 The systems recirculation flow for the bio-tower was 22.6 l/min (6 gal/min) for the start-up phase and 40.0 l/min (10.6 gal/min) for the test period with a corresponding recirculation of the entire septic tank from 5.7 to 10.1 times a day respectively.
 During the testing period a daily average temperature of 19.3°C (66.7°F) and an average rainfall of 5 l/m² was observed. The FBST system operated at an average influent pH level and temperature of 8.6 and 22.0°C. The average effluent pH and temperature was 8.5 of 20.9°C.
 The installed system reduced on average the influent TS from 79151 mg/l to 43021 mg/l and showed an average reduction of the TDS from 36424 mg/l to 21965 mf/l. The TSS and VSS was reduced on average from 94.1 mg/l to 69.9 mg/l and 89.0 mg/l to 64.9 mg/l.
 NH3-N content was reduced from 57.5 mg/l in the influent to 53.4 mg/l in the effluent. The average BOD and COD was reduced from the average influent value of 88.2 mg/l and 318.2 mg/l to 66.8 mg/l and 256.2 mg/l respectively. However, at the end of the 130-day test period BOD and COD values were the lowest at 15.5 mg/l and 56.0 mg/l respectively, indicating bacteria cultures are well established and the system operation of the FBTS system is mostly constant.
 This research showed that the FBST system can improve operations of a DWWTS system significantly reducing the effluent load over 10 times compared to the influent load of the system.