Search

The implementation of community-level de-centralised anaerobic digestion (AD) systems offers a sustainable solution for organic waste management and energy provision, but there is currently a need for low-cost methods of system control and management at this scale. The problem becomes accentuated with increasing deployment, as greater complexities are created by the need to both monitor and control a wider network of smaller, community-scale plants. This paper describes research to design, deploy and test such a system by creating a network of two independent biogas generation AD reactor sites situated in the United Kingdom and Thailand. Internet of things (IoT) aspects such as inexpensive and widely available open-source control electronics was used in combination with small commercial gas analysers to log, transfer and share data with a central station, achieving real-time monitoring of performance for both networked digesters. The design proved beneficial for collaboration and knowledge exchange purposes along with providing off-site observations on reactor status. This information was used for early intervention to maintain biogas yields and enable the dynamic assessment of process economics. The concept showed potential for upscaling to larger multi-site networks of AD reactors that could maintain process optimisation without the need for skilled staff on site.

Despite their different economic backgrounds, Japan and Sri Lanka share similarities as island nations. As a developing country, Sri Lanka needs to identify the country’s existing situation of Plastic Waste Management (PWM) to improve the circularity in the sector. Japan’s existing PWM strategies are a pointer for Sri Lanka to improve the circularity along the plastic value chain. The main aspects that are considered in this study are quantitative data related to the plastic value chain, plastic recycling technologies, plastic recycling businesses, policies, regulations related to plastic waste management, and public awareness strategies in plastic waste management. The methodology relied on literature review and interviews. The main focus of these interviews was to fill the information gap that was identified during the literature review. Japan is practicing all the stages of the plastic value chain, including virgin plastic production, whereas virgin plastic production is absent in Sri Lanka. Technological and policy advancements like the application of Extended Producer Responsibility (EPR) in PWM in Japan can be used as a means of achieving circularity in the Sri Lankan PWM sector. The well-established informal plastic recycling industry in Sri Lanka is a significant feature compared to Japan’s formal plastic recycling industry.

Sri Lanka, a South Asian country, with a developing economy, is grappling with surging plastic pollution. Japan, on the other hand, is a developed country with a systematic waste management system. Both countries have similarities in terms of being island nations. Japan’s existing plastic waste management (PWM) strategies are a pointer for Sri Lanka to improve the circularity along the plastic value chain. In this study, the aspects of quantitative data related to the plastic value chain, plastic recycling technologies, plastic recycling businesses, policies, and regulations related to plastic waste management, and public awareness strategies in plastic waste management are compared between the two countries Sri Lanka and Japan. The methodology included the literature review and survey conducted using questionnaires, especially to fill the information gap that is identified during the literature review. Japan is practicing all the stages of the plastic value chain, including virgin plastic production, whereas virgin plastic production is absent in Sri Lanka. Technological and policy advancements like the application of Extended Producer Responsibility (EPR) in plastic waste management in Japan can be used as a means of achieving circularity in the Sri Lankan plastic waste management sector. The well-established informal plastic recycling industry in Sri Lanka is a significant feature compared to Japan’s formal plastic recycling industry. The school curriculum in Japan which includes ways of creating awareness on plastic waste management is a proactive action to combat plastic pollution, which is another idea for Sri Lanka to emulate its endeavor to reach circularity in plastic waste management.

The membranes of a Membrane Aerated Biofilm Reactor (MABR) function as bubble-less air diffusers and bio-carriers. Recent bench-scale experiments reported that the shape of membranes influenced the oxygen transfer and utilization rates, which in turn affected the pollutant removal performance of the MABR. In this study, two pilot-scale MABRs using multi-layer hollow fiber membranes with the relaxation rates of 0.1-1.8% (MABR 1) and 1.0-2.8% (MABR 2) were used for the treatment of organics and nitrogen in real medium-strength domestic wastewater. Higher-relaxation-rate membranes have loose and more curved fiber bunch that may allow biofilm to grow more easily and let air diffuse more efficiently. MABR 2 had achieved better performance than MABR 1 at 12- and 6-h Hydraulic Retention Time (HRT), with respectively 0.7-4.3%, 17.7-18.1%, and 5.5-9.0% higher removal efficiencies for Chemical Oxygen Demand (COD), Ammonia Nitrogen (NH

Marine plastic pollution has become a major threat to the ecosystem. The increasing production and use of plastic, combined with limitations of waste management practices, mean the leakage of plastic waste into the environment is bound to increase. This study focuses on the determination of plastic recovery potential from dumpsites and landfills in Thailand, to potentially prevent marine plastic pollution. In this study, two dumpsites were analysed wherein an average of 42% of plastic was found to be present. This value, when extrapolated for Thailand, is equivalent to 187.9 million tonnes of plastic waste in dumpsites and landfills. While there are 2380 dumpsites in the country, this study suggests that 973 of these spread over 42 provinces are located near water bodies or coastline, which should be considered as a priority. The plastic waste recovered from these dumpsites can be treated by co-fuelling in cement industries. Cement kilns can valorise plastic waste as they can reach up to 75% energy recovery from waste, which is much higher compared to traditional waste-to-energy plants. With adequate incentives and sound regulations, cement industries could help in the reduction of marine plastic pollution with controlled emissions and a very large capacity to co-fuel cement production, there is a readily available solution to manage the large volumes of solid waste generated.

The increasing generation of solid waste and its improper management has imposed daunting impact on Kabul city. The city of 5 million people generated 3050 tonnes of solid waste every day in 2018. Data analysis shows that if an estimated 25% waste reduction is achieved gradually by 2023, then the total cost of the system will be reduced to 1505.9 million Afs/year, much lesser than the estimated cost at 2210 million Afs/year. This study was aimed at developing an integrated solid-waste management (ISWM) plan for Kabul city based on an overview of the existing system and practices, including the gaps in the entire value chain. The study recommends a paradigm shift from business-as-usual scenario to an ISWM approach. The proposed strategies, when implemented effectively, will increase the recycling rate and reduce the requirement for landfilling in Kabul city. Policy reforms to encourage waste reduction and segregation, and the establishment of facilities for recycling, treatment, and landfilling are proposed. Moreover, the willingness to pay of citizens indicates the total cost of waste management system, estimated at 111.53 million Afs/month, can be recovered effectively.

The microbial endogenous respiration process is very important in biological water treatment processes. This study analyzed and compared the endogenous respiration process in an attached growth membrane bioreactor (aMBR) system and a UV/O3 integrated aMBR system (UV/O3-aMBR) in treating polluted surface water with CODMn around 10 mg/L. The endogenous respiration activity of heterotrophic microbes and autotrophic nitrifiers activity in both systems was analyzed and compared. Results show that heterotrophic bacteria and autotrophic nitrifiers enter endogenous respiration at 6 h aeration in an aMBR and 0 h in a UV/O3-aMBR system. Biomass amount on PVA-gel in aMBR was higher than in UV/O3-aMBR in terms of specific respiration rates SOURt, SOURH, and SOURA. Substrate remained on PVA-gel in the aMBR system, but no substrate remained on PVA-gel in the UV/O3-aMBR system. Higher species of microbes, including recoverable and irrecoverable components, existed in the aMBR system as compared to the UV/O3-aMBR system. The UV/O3-aMBR system could make full use of the advanced oxidation process (AOP) and biological process, leading to a higher treatment performance, and has the potential to mitigate total energy demand. Thus, the UV/O3-aMBR system can be used as a new technology for treating polluted surface water with the co-contribution of biological process and AOP treatment.

A pilot scale decentralised Continuously Stirred Tank Reactor (CSTR) was designed, developed and installed, with 675 L working volume, to treat food waste generated from the Asian Institute of Technology (AIT) campus community. The reactor was operated in mesophilic, anaerobic and wet condition with feedstock as food waste of 10% Total Solids (TS) content. This study aims for performance evaluation of food waste anaerobic digestion and development of remote monitoring system suitable for centralised monitoring of decentralised anaerobic digestion plants. The performance of the reactor was remotely monitored with the installation of pH, Temperature and Oxidation Reduction Potential (ORP) electrodes connected with the Programmable Logic Controller (PLC). The quality of biogas produced was monitored by online biogas analyzer system. The CSTR was operated with three different Organic Loading Rates (OLR) viz., 1, 2 and 3 kg of volatile solids per cubic meter of digester per day (kg VS/m3.d) to evaluate performance of the food waste digestion and biogas production. The average biogas yield was 0.75, 0.62 and 0.52 cubic meter per kilogram of volatile solids (m3/kg VS), with average methane yield of 0.42, 0.33 and 0.27 m3/kg VS at OLR of 1, 2 and 3 kg VS/m3.d respectively. Furthermore, it was observed that the average reduction in total solids was 70.7, 66.5 and 54.98% and average reduction in volatile solids was 78.3, 72 and 67% at OLR of 1, 2 and 3 kg VS/m3.d respectively. Internet of Things (IoT) enabled remote monitoring on real time basis and aided the centralised operator to improve the process performance resulting in better operation and maintenance of the decentralised anaerobic digestion systems.

This study is aimed to comprehend the treatment of non-submerged attached growth systems using bio-sponge, bio-cord, and bio-cloth media. Three reactors were set up with internal recirculation ratio of 1 (IR = 1) and similar media surface area. Bio-sponge and bio-cloth reactors showed removal of COD (79 vs. 76%) and NH4+–N (78 vs. 73%). While bio-cord treatment was deteriorated due to time-dependent process. Multiple linear regression revealed that alkalinity governed the formation degree of the anaerobic zone in bio-sponges, partially affecting nitrification. Increasing IR from 1 to 3 caused sloughing of the attached biomass and was positively correlated with effluent nitrite nitrogen concentration, indicating the sensitivity of nitrification to spatial distribution effects. In addition, bio-sponge system obtained superior performance at IR of 2 while bio-cloth one might be also an effective media for wastewater treatment if having good durability.

The ongoing fourth industrial revolution, Industry 4.0 (I4.0), is transforming various industries across the globe. At the same time, resource scarcity with high consumption rates has led to the development of the circular economy. Both concepts advocate for sustainable growth and waste minimization. In developing countries, the integrated solid waste management framework is undergoing modification under I4.0 and the circular economy. Urban local bodies are often unable to measure the readiness of their waste management systems to transform under I4.0 and the circular economy. Here the novel concept of Waste 4.0 is developed. ‘Waste 4.0’ is a readiness assessment tool to promote the comprehensive transformation of municipal solid waste management under I4.0 and circular economy. This tool has eight determinants for assessing the municipal solid waste management of urban local bodies. To validate Waste 4.0 the urban local bodies of Indore and Sagar, India were used as case studies. The readiness index for I4.0 in the municipal solid waste management system in Indore and Sagar was 0.72 and 0.14, respectively. The readiness index for circular economy focus in Indore and Sagar was 0.65 and 0.13, respectively. The Indore urban local body was classified as an ‘Experienced’ player for I4.0 Intervention and a ‘circular economy fast adopter’ for circular economy focus under I4.0 readiness. The Sagar urban local body was classified as a ‘Hesitator’ player for I4.0 Intervention and achieved the ‘Business as usual’ tag for circular economy focus under I4.0 readiness. With the Waste 4.0 assessment results urban local bodies can better plan and thus transform their municipal solid waste management systems under I4.0 and the circular economy.

Biological treatment for volatile organic compound (VOC)–contaminated wastewater with conventional aeration methods causes significant stripping loss of pollutants due to its high volatilit...

The main aim of this study was to evaluate the performance of an air membrane bioreactor (aMBR) for the treatment of gas-phase methanol. A laboratory-scale hollow fiber aMBR was operated for 150 days, at inlet methanol concentrations varying between 2 and 30 g m−3 and at empty bed residence times (EBRT) of 30, 10 and 5 s. Under steady-state conditions, a maximum methanol removal efficiency (RE) of 98% was obtained at an EBRT of 30 s and a decrease in RE of methanol was observed at lower EBRTs. On increasing the inlet loading rate, some portion of gas-phase MeOH was stripped into the liquid phase due to its solubility in water. Under transient conditions, the MeOH removal efficiency dropped from an average value of 95%–90% after 5 h of 10-fold shock load and dropped from an average value of 95%–88% under 5-fold increase in shock load. During transient-state tests, the aMBR performed well under different upset loading conditions and a drop in RE of ∼ 5–10% was observed. However, the aMBR performance was restored within 1–2 days when pre-shock conditions were restored. The results from microbial structure analysis revealed a big shift of the dominant methanol degrader, from Candida boidinii strain TBRC 217 to Xanthobacter sp. and Fusicolla sp., respectively.

An initiative has been made by Government agencies responsible for solid waste management in Sri Lanka with the support of the UN-Habitat to improve poor waste management practices. The existing databases were revised. It is reported that the present collection efficiency is 27.2% out of the generation of 7210 tons/day. The non-biodegradable, including plastic is 382–475 tons/day. Of these, 4933 tons/day is disposed at the point of generation, most of which are burnt. The plastics account for 232 tons/day, emitting dioxins and furans of 10–14 kg/day. Therefore, it was necessary to quantify some of the major issues and best practices so as to formulate financial mechanisms to revise the new policy on waste management. An Evidenced Based Informative Database is under construction to enable updating of a Comprehensive Integrated Solid Waste Management Plan (CISWMP) and this consists of sub-plans at Local Authority, Provincial Council, and National levels. The National plan aims to substantially improve upon the ways and means of increasing collection efficiency to at least 50%, for safe disposal in landfills and increase recycling to divert waste. It will cost 2.2 USD per capita per annum for 50% of the population above the local taxes.

This study used UV/O3-aMBR system for treating polluted surface water with CODMn around 10 mg/L, to improve the removal of non-biodegradable components. UV/O3 was used in the recirculation stream, partially treating the recalcitrant in aMBR permeate to improve its biodegradability, and then send back to aMBR for biodegradation. Removal performance of UV/O3-aMBR system with recirculation ratio 20, 40, 60 and 80% was tested and compared. The removal of CODMn, UV254 and NH3-N increased with the increment of recirculation ratio. UV/O3-aMBR system has higher recalcitrant removal performance and less membrane fouling. The fluorescent dissolved organic matter (FDOM) was largely reduced in UV/O3-aMBR system, and the system hydrophilicity was higher than aMBR system. The Modified Stover Kincanoon model was able to describe UV/O3-aMBR system; and has higher Umax than aMBR system. UV/O3-aMBR can be develop as an effective technology in improving recalcitrant removal in polluted surface water treatment.

Surface water has been facing increasing loads of various types of organic contamination due to human activities. Attached growth membrane bioreactor (aMBR) has been reported as a promising approach in treating polluted surface water. By using bio-carrier to provide biodegradation and utilize organic pollutants as substrates, aMBR was able to integrate biodegradation and physical rejection in one system. The filling ratio of polyvinyl alcohol gel (PVA-gel), which is an important bioprocess contributor in an aMBR system, was analyzed by batch test and lab-scale aMBR in this study. Batch test with various filling ratios (2%, 5%, 10%, 15% and 30%) were carried out. Oxygen uptake rate (OUR) and specific oxygen uptake rate were used for the comparison of bioactivities. Five percent filling ratio had the highest OUR results of 3.6 mg/L h obtained from the batch test. The chosen filling ratios were tested in a lab-scale aMBR system with hydraulic retention time (HRT) of 1, 2, 2.5 and 3 h. Results shown that at HRT 2.5 h, the aMBR system had the lowest membrane fouling. PVA-gel was able to reject more organic matters than a naturally immobilized membrane bioreactor system, and thus mitigated membrane fouling in the aMBR system.

Following the rapid proliferation of organic pollutants in the surface water, the application of microfiltration technology has been extensively studied for its treatment since the 1990s. Given that the conventional treatment processes were unable to treat the excessive dissolved organic compounds, microfiltration technologies have gained momentum as effective solutions to treat the surface water. The efficacy of low-pressure membrane filtration technologies such as microfiltration and ultrafiltration has been under scrutiny ever since, and numerous research studies have aimed at enhancing their capabilities to reject the suspended solids and organic matters. This paper reviews the development trajectory of membrane technology, ranging from microfiltration to membrane bioreactors, for treating dissolved organic matters in surface water and their future potential. This is a critical review of the physicochemical and biological options such as, but not limited to, pretreatment of water using coagulation, ozonation, adsorption and/or a combination of these. On the whole, it is concluded that the membrane bioreactor system, which combines biological process and physical rejection, showed high potential in treating polluted surface water, which needs to be further investigated extensively to promote its application in water treatment plants.

The status of circular economy (CE) in Thailand is reviewed in this chapter. The current CE practices and policy instruments used towards sustainable resource management in Thailand are presented as well. CE indicators for Thailand are extensively studied and summarized in the paper. Based on the review, it is established that the existing policies and programs on CE are focused more towards 3R concepts and less on other sub-sects of CE such as products-as-services, next life sales, product transformation, collaborative consumption, etc. Currently, CE indicators are primarily based on 3R concepts, whereas it is recommended that the other sub-sects of CE should also be taken into consideration to measure the actual CE progress. Employing packaging waste in Thailand as a case study, the current circular economy practice and key barriers to CE implementation were assessed to propose appropriate policy measures for sustainable waste and resources management. There has been an increase in packaging waste in the municipal solid waste (MSW) stream, of which plastic poses a key challenge in the urban waste stream. The current flow of packaging waste is predominated by recycling as downcycling. Most packaging waste remaining at landfills is one-time-use packaging. According to the comprehensive assessment, consumers had positive attitudes towards 3R practices and were conscious of waste problems. Economic incentives and regulatory instruments in line with a new waste management policy framework are recommended to overcome the barriers hindering CE implementation. Packaging waste management policy framework and policy measures are established through this study.

© 2019 Elsevier Ltd Microplastics can enter freshwater lakes through many sources. They can act as carriers to adsorb bacteria, virus, or pollutants (e.g., heavy metal and toxic organic compounds) that threaten human health through food chain. Microplastics can exist in surface water and sediments in freshwater lakes after they enter the lakes through discharge points. Wastewater discharge is the main cause of lake eutrophication and is the main emission source of microplastics. The correlation between lake trophic state and microplastic abundance has been rarely reported. This study investigated the microplastic contamination in surface water and sediments of 18 lakes along the middle and lower reaches of the Yangtze River Basin in the period of August–September 2018. The correlation between lake trophic state and microplastic abundance in surface water and sediments was investigated and discussed. The microplastic abundance in surface water was approximately two orders of magnitude lower than that in sediments in all 18 lakes. Hong Lake had the highest microplastic abundance in surface water sample, and Nantaizi Lake had the highest microplastic abundance in sediment sample. The dominant microplastic shape was fiber of 93.81% in surface water sample and 94.77% in sediment sample. Blue-colored microplastics were dominant in nearly all lakes in surface water sample (around 40%–60%) and sediment sample (around 60%–80%), followed by purple- and green-colored ones. The microplastics size

Online shopping, a form of electronic commerce (e-commerce), is a type of business where buyers and sellers interact electronically (using the Internet channel) for the exchange of goods and services and payments of the transaction. E-commerce offers positive environmental effects, for example, greenhouse gas emission reduction due to reduced traveling needs by individual consumers, and other energy use in traditional brick-and-mortar shops. However, online shopping is not entirely free from negative environmental impacts. Packaging waste from e-commerce is one of such concerns. A typical e-commerce parcel may use up to seven types of packaging materials: paper bills, envelopes, cardboard box, plastic bags, woven bags, tape, and buffer materials (bubble wrap, styrofoam). Environmental impacts of online shopping can be categorized into first-order (information and communication technology equipment usage), second-order (changing of processes and markets affecting the logistics system for product fulfillment and delivery), and third-order (rebound) effects. Thai e-commerce market is advancing to become one of Asia’s top performers. According to the Electronic Transactions Development Agency, the value of the Thai e-commerce market in 2016 was expected to reach 2,523.99 billion Baht. At present, Lazada is a popular business-to-consumer e-commerce company in Thailand. A survey conducted to identify consumers’ awareness and willingness to reduce environmental impacts of online shopping revealed that a 13.8% of the respondents had never purchased anything via the online channel, citing lack of opportunity to touch/feel the product, and fear of deception being the reasons. Of the online shoppers (86.2%), only 11.8% felt that the product arrived with an ‘excessive’ packaging, and they, however, simply discard those packaging materials. In order to transform e-commerce into Green commerce, companies need to invest in packaging innovation and sustainable supply chain mechanisms including reverse logistics system to promote reuse and recycling, while consumers also need to display sustainable consumption behavior.

A pilot-scale membrane-aerated biofilm reactor (MABR) modified with Polyvinyl Alcohol (PVA) gel bio-carriers containing denitrifying bacteria was operated with the purpose of enhancing total nitrogen removal efficiency from actual domestic wastewater. MABR system was operated under 6, 9 and 12 h of hydraulic retention times (HRT) in different time periods. Addition of the bio-carriers increased nitrification and total nitrogen removal efficiencies by maximum of 11% and 18% at 12 h of HRT respectively. Maximum of 88% of nitrification and 79% of total nitrogen removal efficiencies were reported in the PVA gel modified MABR. Organic matter removal performance was mostly maintained above 90% with insignificant improvements. In addition to this, natural pH increase observed after PVA gel addition paves a new way for potential cost reduction in industrial scale MABR applications. Low sludge volume index around 80 mL/g indicated rapid settling characteristics of produced sludge.

The increasing organic contamination of surface water hinders the conventional tap water treatment process. Membrane bioreactors (MBRs) are a promising alternative technology for recovering water from polluted surface water. In this study, the composition changes of dissolved organic matters (DOMs) in MBR and ultraviolet/ozone (UV/O3)-MBR systems for polluted surface water treatment were investigated using Orbitrap mass spectrometry analysis with unknown screening. The intense DOM ions within a mass-to-charge ratio range of 100–500 was detected, and 2340 molecular formulae from 5743 peaks were assigned to the two systems. The most abundant components were formulae with C, H, O, N, and CHO only classes. The highest formulae decrease including CHO, CHON, CHOS, and CHONS were attributed to the bio-carrier used in both systems. Results showed that bioprocess was the main contributor in the DOM reduction, and the integration of UV/O3 into the MBR improved the DOM composition changes. Biodegradable components with low O/C ratio in the CHO and CHON classes remarkably increased in the UV/O3-MBR system. The integration of UV/O3 as a polishing step in the recirculation stream of MBR system was effective in improve the DOM removal.

Purpose This paper aims to describe the effects of 3R (reduce, reuse and recycle) waste management initiatives on a campus community. It ascertains the environmental attitudes and opinions of the residents and investigates their behavioral responses to waste management initiatives. Practical implications for enhancing sustainable waste management are discussed in this paper. Design/methodology/approach Demonstration projects on waste segregation and recycling, as well as waste a reduction campaign, were set up on the campus to ascertain people’s attitudes and investigate their behavioral responses toward 3R practices. Data were collected through a questionnaire survey, observations, interviews and the project’s document review. A waste audit and waste composition analysis was carried out to assess waste flows and actual waste management behaviors and measure the change in the recycling rate. Findings 3R waste management initiatives had positive effects on people’s attitudes about resources, waste management and consciousness of the need to avoid waste, but these initiatives did not affect recycling and waste management behavior. A voluntary approach-only cannot bring about behavioral change. Incentive measures showed a greater positive effect on waste reduction to landfills. Nevertheless, the demonstration projects helped to increase the overall campus recycling from 10 to 12 per cent. Originality/value This paper addresses a literature gap about the 3R attitudes and resulting behavior as part of campus sustainability of higher education institutions in a developing country. The authors’ results revealed hurdles to be overcome and presents results that can be compared to behavioral responses of people from other developed countries. These findings can be used as a guide for higher education institution’s policy-makers, as they indicate that voluntary instruments alone will not yield effective results, and other mechanisms that have an impact on people's behavior are required.

The industrial manufacturing of a commodity as well as service sectors, such as drinking water supply systems, is responsible for environmental impacts across its supply chain. Lowering these impacts at each stage of the supply chain is often termed green supply chain management (GSCM). This study assesses energy use, waste generation, chemical use, consumptive water use, and GHG emissions in typical drinking water treatment plant (WTP) operations in Lao PDR, Thailand, and South Korea and consolidates these supply chain impacts broadly into water footprint (WF) and carbon footprint (CF). The respective CFs were found to be 9.4, 375.4, and 359.5 g CO2-eq, while the respective WFs were 335.4, 501.4, and 300.4 L/m3. Among the three countries of the study, only South Korea has implemented various greening activities, such as energy management systems, sludge reuse, GHG target management, and renewable energy development, for meeting its strict government policy and regulations. WTPs in Lao PDR and Tha...

Membrane bioreactor (MBR) is an advantageous technology for wastewater treatment. However, efficient nutrient removal and membrane fouling mitigation remain major challenges in its applications. In this study, an electroconductive moving bed membrane bioreactor (EcMB-MBR) was proposed for simultaneous removal of organics and nutrients from domestic wastewater. The EcMB-MBR was composed of a submerged MBR, filled with electrodes and free-floating conductive media. Conductive media were introduced to reduce energy consumption in an electrochemical MBR, to improve nitrogen removal, and to mitigate membrane fouling. The results showed that COD, total nitrogen, and total phosphorus removal was up to 97.1 ± 1.4%, 88.8 ± 4.2%, and 99.0 ± 0.9%, respectively, in comparison with those of 93.4 ± 1.5%, 65.2 ± 5.3%, and 20.4 ± 11.3% in a conventional submerged MBR. Meanwhile, a total membrane resistance reduction of 26.7% was obtained in the EcMB-MBR. The optimized operating condition was determined at an intermittent electricity exposure time of 10 min-ON/10 min-OFF, and a direct current density of 15 A/m2. The interactions between electric current and conductive media were explored to understand the working mechanism in this proposed system. The conductive media reduced 21% of the electrical resistivity in the mixed liquor at a selected packing density of 0.20 (v/v). The combination of electrochemical process and conductive media specially enhanced the reduction of nitrate-nitrogen (NO3--N) through hybrid bio-electrochemical denitrification processes. These mechanisms involved with electrochemically assisted autotrophic denitrification by autotrophic denitrifying bacteria. As a result, 5.2% of NO3--N remained in the effluent of EcMB-MBR in comparison with that of 29.5% in the MBR. Membrane fouling was minimized via both mechanical scouring and electrochemical decomposition/precipitation of organic/particulate foulants. Furthermore, a preliminary cost analysis indicated that an additional operating cost of 0.081 USD/m3, accounting for 10 - 30% increment of the operating cost of a conventional MBR, was needed to enhance the nitrogen and phosphorus removal correspondingly in the EcMB-MBR.

This study demonstrates a feasible and novel design of the up-concentration of domestic sewage through the Biosorption-Sedimentation Process (BSP). In this study, the system was operated at relatively shorter ratios of anoxic to anaerobic hydraulic retention times (Tano/Tan) with an infinite sludge retention time (SRT) to obtain an up-concentrated stream in terms of chemical oxygen demand (COD) and total phosphorous (TP) and ammonium-nitrogen removal in the effluent. Results indicate that the system has a potential of net energy yield up to 15.5 kW h/m3. Tano/Tan of 60 min/60 min was selected as an optimized run based on Carbon: Nitrogen: Phosphorous (C:N:P) ratio, ammonium-nitrogen concentration, and the maximum energy potential in terms of COD. For process optimization, Response Surface Methodology (RSM) was applied. The optimized run predicted by RSM against the required responses (COD, TP, NH4+-N and TKN) was almost the same as obtained from C:N:P ratio. To conclude, BSP system is not only capable of producing an up-concentrated effluent stream but also has a potential to yield biogas via anaerobic digestion (AD).

Anaerobic digestion has emerged as the preferred treatment for organic fraction of municipal solid waste. Digestate management strategies are devised not only for safe disposal but also to increase the value and marketability. Regulations and standards for digestate management are framed to address the pollution concerns, conserve vulnerable zones, prevent communicable diseases, and to educate on digestate storage and applications. Regulations and the desired end uses are the main drivers for the enhancement of digestate through pretreatment, in vessel cleaning, and post-digestion treatment technologies for solid and liquid fractions of digestate. The current management practice involves utilization of digestate for land application either as fertilizer or soil improver. Prospects are bright for alternative usage such as microalgal cultivation, biofuel and bioethanol production. Presently, the focus of optimization of the anaerobic digestion process is directed only towards enhancing biogas yield, ignoring the quality of digestate produced. A paradigm shift is needed in the approach from ‘biogas optimization’ to ‘integrated biogas–digestate optimization’.

Anaerobic co-digestion in thermophilic condition leads to efficient waste treatment and energy recovery through accelerated and enhanced synergism. The performance of anaerobic co-digestion of food waste with chicken manure was investigated for overcoming the challenges due to process inhibition during mono-digestion of food waste. The bench scale anaerobic Continuously Stirred Tank Reactor (CSTR) system with the working volume of 87 L in wet condition with 10% total solids content was used for this study. Though thermophilic food waste anaerobic digestion indicated high methane yield and solids reduction, the process stability was affected at higher loading. Whereas, the reduction in FOS/TAC value (the ratio of volatile fatty acids to total alkalinity) through co-digestion indicated the higher capacity for organic loading rate in the anaerobic co-digestion system due to synergistic effect of microorganisms, buffering capacity and nutrient balance by C/N adjustment in the feedstock. Moreover, the percentage increases of specific methane yields in co-digestion compared with mono-digestion was found to be 33.2%, 10.4%, 12.1% and 89.9% at organic loading rates (OLR) of 1, 2, 3 and 4 kg VS‧m−3‧d−1 respectively, as a consequence of the improvement in stability through co-digestion.

The policies and technological drivers to manage food waste in Asia have been shaped by the increasing awareness of the countries to this issue, their commitment to national and international development goals, their socio-economic constraints, and their recognition of the potency to recover nutrients and energy from food waste. The concept of reduce, reuse and recycle (the 3R principles) streamline the existing food waste management policies, and scrutinising the gaps and challenges led to a conclusion that most of the countries emphasise food waste segregation and treatment instead of prevention at source itself. Furthermore, a qualitative SWOT analysis of five prevailing treatment options led to a conclusion that animal feeding, incineration, and landfilling are unsustainable since they pose various health and environmental hazard risks. It was further concluded that anaerobic digestion was the preferred option than aerobic digestion (composting) considering the characteristics of the available food waste in Asia as well as the underlying environmental and economic benefits. Moreover, decentralised, community-scale, anaerobic digestion system has been gaining traction over centralised, large-scale system because of their lower energy footprint, ease of operation, need for lesser resources, lower operation and maintenance costs, and higher chances of public acceptance. It was also observed that the policy to gain energy from segregated food waste is a larger driving force for the efforts to promote anaerobic digestion and thereby manage food waste sustainably.