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The palm oil industry is gearing itself towards sustainability by implementing mandatory biogas capture for all palm oil mills in the effort to reduce greenhouse gases. This action also indicates that the anaerobic digestion of palm oil mill effluent (POME) will be one of the essential sources of biogas for energy generation. However, the availability of POME is limited during the low crop season due to the lower palm oil production. Concurrently, the solid wastes known as empty fruit bunches (EFB) are also produced from the oil mill. EFB has vast potential for power generation, though it is currently not being fully utilized. Therefore, this work aims to enhance the biogas production from anaerobic co-digestion (ACD) of EFB with POME by evaluating the effect of alkaline pretreatment of EFB, EFB-to-POME ratio, and temperature on the methane yield. The optimum EFB:POME ratio is 0.6:1 as the methane production of this ratio at both thermophilic and mesophilic conditions are relatively high (up to 74.02 ml CH4/g VS). Results show that ACD performs 2.36 times better than mono-digestion of POME at mesophilic conditions. The modified Gompertz model could predict the process behavior of the ACD of EFB with POME with high R2 (>0.95). Further investigation on other potential pretreatment methods and synergism analysis of co-digestion, which provides a balance between efficiency and economy could be carried out. The impact of this work will be towards a sustainable environment, which will significantly reduce the environmental impacts of palm oil production.

The rapid increase in demand for renewable energy has led to a need for more efficient and effective ways to produce biogas from palm oil mill effluent (POME), which is rich in biological and chemical oxygen demand (BOD and COD). Despite its potential as a source of biogas, POME is not always effectively utilized in biogas production due to a lack of optimization of the treatment process. This study aims to address this issue by identifying the critical parameters affecting biogas production from POME and optimizing the process for maximum biogas yield and COD removal. This study employed comparative analysis and response surface methodology to optimize the performance of palm oil mill effluent (POME)-based biogas plants in Malaysia. Historical data from three commercial POME-based biogas plants in Malaysia were analyzed to identify the most critical parameters for biogas yield and COD removal. Response surface methodology, using Box–Behnken design and Design-Expert software, was then used to optimize these parameters. Sensitivity analysis was performed to interpret the impact of parameters on biogas production, with Organic Loading Rate (OLR) found to be the most critical factor for methane yield. The results showed that the optimum conditions for maximum methane production were OLR of 1.23 kg/m3·day, inlet Total Solids (TS) of 46,370 mg/L, pH of 4.5, and temperature of 45.4 °C, resulting in a 39.6% increase in methane yield (0.335 m3 CH4/kgCODremoved) and a 1.1% increase in COD removal (93.4%).

The alarming rise of food waste all over the world due to population and economic growth must be tackled with better waste management and treatment methods. The current practice of landfilling has been scientifically proven to adversely impact environmental and societal health. A relatively new technology called hydrothermal carbonization (HTC) has the potential to solve this problem. It takes in high-moisture-content material, like food waste, and converts it into bio-coal with a heating value similar to normal coal. The present study explored the feasibility of HTC technology and bio-coal production in Malaysia. An in-depth study via desk research was conducted by implementing Porter’s five forces analysis to evaluate the feasibility of the bio-coal production project. A survey involving 215 respondents from different households that represent the average demography of Malaysia was also conducted to understand the behaviors and attitudes of different households towards food waste. The present study found that a typical Malaysian household disposes mostly of meal leftovers, with an average of 926 g of food waste per day. In addition, the 3 highest food categories that were disposed of were rice or noodles or pasta (13.0%), vegetables (12.2%) and curry and soup (10.1%). Meal leftovers such as curry and soup are high in moisture content, which is suitable for HTC. The survey on household waste provided adequate information to support the availability of a sufficient quantity of food waste in the country to sustain the raw material for the bio-coal project in Malaysia. Furthermore, a consumer survey involving seven industrial firms was conducted to determine the potential buyers of bio-coal. The responses from the industrial firms show that a bio-alternative for coal is important, and they are willing to transition to greener technologies. However, five out of seven firms stated that the main hurdle in adopting bio-coal is the high cost of production and incompatibility with existing industrial processes. Finally, interviews were conducted with key players in the industry to evaluate the adoptability of bio-coal into the wider market. The findings from the desk research and the primary research show that the outlook for bio-coal in the market is quite positive. In the long run, HTC is certainly profitable, but for immediate benefits, adequate government support and policy in favour of the use of HTC bio-coal in power plants are required.

Palm oil plays a vital role as edible vegetable oil for daily human consumption. However, the process technologies and the quality of palm oil produced have remained stagnant for the past decades. ...

The treatment of palm oil mill effluent (POME) has always been the topic of research in Malaysia due to the high concentration of total suspended solid (TSS) and oil and grease (O&G) ranges from 28 846 to 30 920 mg/L and 5614 to 8812 mg/L, respectively. Additionally, the release of methane gas during the treatment of POME in all of the palm oil mills has been the major contributor to greenhouse gas (GHG) effect. The main aim of this work is to evaluate the performance of the pilot-plant integrated anaerobic–aerobic bioreactor (IAAB) for POME treatment at two different phases: (a) startup and (b) long-term performance evaluation from an organic loading rate (OLR) of 10.5 to 32.5 gCOD/(L·day). Startup of the pilot-plant IAAB was successfully accomplished in 24 days with overall removal efficiencies in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solid (TSS) of at least 90% at the OLR of 8.0 gCOD/(L·day). The pilot-plant IAAB achieved high BOD, COD, and TSS removal efficiencies of more than 99% for OLR up to 30.0 gCOD/(L·day) with methane yield ranges from 0.0406 LCH₄/gCODᵣₑₘₒᵥₑd to 0.1312 LCH₄/gCODᵣₑₘₒᵥₑd. The effluent quality remained stable with BOD of 16–107 mg/L with a high percent of compliance with the discharge limit of 100 mg/L. The coupling of the Grau second-order and Stover–Kincannon models (anaerobic system) with the Stover–Kincannon model (aerobic system) will completely define the pilot-plant IAAB system. This pilot-plant research will provide valuable data and experiences required to design and commission a full-scale IAAB.

This paper studies the effect of addition of Zn and ultrasound-assisted co-precipitation on Cu-Mn oxide catalysts for the oxidation of CO. Cu-Mn-Zn oxide catalysts were synthesised at different molar ratios and characterised and evaluated for CO oxidation performance. Scanning electron microscopy (SEM) imaging showed that the morphologies and textural properties of the catalysts were markedly affected by the different synthesis conditions, notably the formation of different geometries of various sizes depending on the Zn loading used. Characterisation results also revealed that both the addition of Zn and the use of ultrasound-assisted synthesis improved the dispersion of metal constituents in the mixed oxide phase, evident from the lower peak intensity and smaller crystallite sizes and more dispersed particles as seen in SEM imaging. Gas adsorption results revealed that Zn loading influences the porosity and adsorption capability of the catalyst. Zn-loaded samples exhibited a H3 hysteresis loop, which suggests the presence of slit-like pores. Temperature-programmed reduction results indicate that sonicated samples exhibit improved reduction capabilities which can increase overall catalytic activity. Results showed that Cu/Mn/Zn = 2:1:0.5 displayed the highest activity, showing 76.0% and 82.8% for CO and SO2 at 130 °C, respectively. This work has confirmed that the addition of 0.5 molar ratio of Zn and the presence of ultrasonic treatment during the catalyst synthesis have improved the overall catalytic performance, while further addition in Zn concentrations resulted in an adverse effect on the catalyst.

Endocrine disruptor compounds (EDCs) such as plasticisers, surfactants, pharmaceutical products, personal care products and pesticides are frequently released into the environmental waters. Therefore, a sensitive and environmentally friendly method is entailed to quantify these compounds at their trace level concentrations. This study encapsulated the β-cyclodextrin crosslinked with citric acid in a polypropylene membrane protected-μ-solid phase extraction (BCD-CA μ-SPE) device for preconcentrating the EDCs (triclosan, triclocarban, 2-phenylphenol, 4-tert-octylphenols and bisphenol A) in real water samples before the analysis by high-performance liquid chromatography. FT-IR and TGA results indicated that BCD-CA was successfully synthesised with the formation of ester linkage (1078.33 cm

As the population increases, energy demands continue to rise rapidly. In order to satisfy this increasing energy demand, biogas offers a potential alternative. Biogas is economically viable to be produced through anaerobic digestion (AD) from various biomass feedstocks that are readily available in Malaysia, such as food waste (FW), palm oil mill effluent (POME), garden waste (GW), landfill, sewage sludge (SS) and animal manure. This paper aims to determine the potential feedstocks for biogas production via AD based on their characteristics, methane yield, kinetic studies and economic analysis. POME and FW show the highest methane yield with biogas yields up to 0.50 L/g VS while the lowest is 0.12 L/g VS by landfill leachate. Kinetic study shows that modified Gompertz model fits most of the feedstock with R 2 up to 1 indicating that this model can be used for estimating treatment efficiencies of full-scale reactors and performing scale-up analysis. The economic analysis shows that POME has the shortest payback period (PBP), highest internal rate of return (IRR) and net present value (NPV). However, it has already been well explored, with 93% of biogas plants in Malaysia using POME as feedstock. The FW generation rate in Malaysia is approximately 15,000 tonnes per day, at the same time FW as the second place shows potential to have a PBP of 5.4 years and 13.3% IRR, which is close to the results achieved with POME. This makes FW suitable to be used as the feedstock for biogas production.

This chapter identifies the potential of using an efficient biogas prototype known as integrated anaerobic-aerobic bioreactor (IAAB) system for the treatment of palm oil mill effluent (POME). Additionally, design procedures and design considerations of the IAAB will be discussed in detail as well. The IAAB system implicates a small footprint, shorter hydraulic retention time (HRT), and ability to treat liquid effluent at high loading rates as compared to the conventional biogas technologies. The positive results obtained by the laboratory-scale IAAB (COD removal and total suspended solid [TSS] removal more than 99%) results in upscaling the volume of the IAAB from 55 L to 1.8 m3. It will act as a commercialization prototype for the palm oil industry to accept such a new approach to combat the massive volumes of POME produced daily and unstable characteristics of POME obtained during low- and high-crop seasons of fresh fruit bunch (FFB). Positive results were obtained whereby the IAAB was successfully operated at an organic loading rate (OLR) of 30.0 gCOD/L.day with overall removal efficiency of >99%. Additionally, the final treated effluent produced abides the discharge limit with biochemical oxygen demand (BOD) less than 20 mg/L. This integrated system follows the concept of zero liquid discharge, whereby all liquid biomasses in the palm oil mill are converted into valuable products, and thus transforming the palm oil industry into a “green industry.”

Anaerobic digestion has been widely employed in waste treatment for its ability to capture methane gas released as a product during the digestion. Certain wastes, however, cannot be easily digested due to their low nutrient level insufficient for anaerobic digestion, thus co-digestion is a viable option. Numerous studies have shown that using co-substrates in anaerobic digestion systems improve methane yields as positive synergisms are established in the digestion medium, and the supply of missing nutrients are introduced by the co-substrates. Nevertheless, large-scale implementation of co-digestion technology is limited by inherent process limitations and operational concerns. This review summarizes the results from numerous laboratory, pilot, and full-scale anaerobic co-digestion (ACD) studies of wastewater sludge with the co-substrates of organic fraction of municipal solid waste, food waste, crude glycerol, agricultural waste, and fat, oil and grease. The critical factors that influence the ACD operation are also discussed. The ultimate aim of this review is to identify the best potential co-substrate for wastewater sludge anaerobic co-digestion and provide a recommendation for future reference. By adding co-substrates, a gain ranging from 13 to 176% in the methane yield was accomplished compared to the mono-digestions.

In the present study, amorphous mesoporous silicon oxycarbide materials (SiOC) were successfully synthesized via a low-cost facile method by using potassium hydroxide activation, high temperature carbonization, and acid treatment. The precursors were obtained from floating plants (floating moss, water cabbage, and water caltrops). X-ray diffraction (XRD) results confirmed the amorphous Si&ndash, O&ndash, C structure and Raman spectra revealed the graphitized carbon phase. Floating moss sample resulted in a rather rough surface with irregular patches and water caltrops sample resulted in a highly porous network structure. The rough surface of the floating moss sample with greater particle size is caused by the high carbon/oxygen ratio (1: 0.29) and low amount of hydroxyl group compared to the other two samples. The pore volumes of these floating moss, water cabbage, and water caltrops samples were 0.4, 0.49, and 0.63 cm3 g&minus, 1, respectively, resulting in thermal conductivities of 6.55, 2.46, and 1.14 Wm&minus, 1 K&minus, 1, respectively. Floating plants, or more specifically, floating moss, are thus a potential material for SiOC production.

Food waste (FW) utilized as substrate for anaerobic digestion (AD) to produce biogas is promising. Simultaneously, waste is handled and value-added products such as biogas and fertilizer are produced. Palm oil mill effluent (POME) is used as the co-substrate. This study aims to simulate the complete process flow of anaerobic co-digestion (AcoD), consisting of pre-treatment of feedstock, biogas upgrading, wastewater treatment and sludge dying using SuperPro Designer. Parameters, namely hydraulic retention time (HRT), recycle ratio of sludge, water to FW ratio (kg/kg) and co-substrate to FW ratio (kg/kg), would affect the performance of digester. The optimization of these parameters is performed using Design-Expert software, involving response surface methodology (RSM). The effects on responses such as methane flow, chemical oxygen demand (COD) and volatile solid (VS) removal efficiencies are analyzed. In treating 25,000 kg/h of feed, the optimized values for HRT, recycle ratio, water to feedstock ratio, POME to FW ratio are 37.2 days, 0.381, 0.027 and 0.004, respectively. The methane yield is 0.30 L CH4/g of COD removed, with COD and VS removal efficiencies of 81.5% and 68.9%, respectively. The project is profitable, with a payback period of 6.14 years and net present value (NPV) of $5,680,000. A comprehensive understanding of AD matures it for commercialization purposes.

Malaysia is experiencing rapid urbanisation leading to an increase in the demand of energy. The use of renewable energy can satisfy energy demands and mitigate environmental issues such as greenhouse gas (GHG) emission. Biogas produced from anaerobic digestion from different feedstock such as food waste (FW), palm oil mill effluent (POME), garden waste (GW), landfill, sewage sludge (SS) and animal manure can be utilised to reduce the need of fossil fuel. This review paper will focus on the current biogas technologies, their scalability and socio-economic analysis on biowastes to energy in Malaysia. If all FW generated in Malaysia (approximately 15,000 tonnes per day) could be converted to energy, it has a potential to replace fossil fuel totally, as it produces 10 times more than the annual requirement of energy. Consequently, there is a significant advantage obtained from offsetting huge amounts of GHG emissions that would otherwise be contributing to the global warming effect. Several issues and challenges have been identified for the scale-up of laboratory scale to industrial scale where parameters including pH, temperature, organic loading rate (OLR), hydraulic retention time (HRT) and mixing rate must be treated carefully. The socio-economic survey conducted as part of this study has revealed the strong acceptability of this technology and the readiness of the population in Malaysia to contribute and be part of this effort. However, the survey has also identified the limitations of the sorting and preparation facilities of food waste segregation for potential biogas generation.

The characteristics of Palm Oil Mill effluent (POME) have captivated attention in harnessing its high organic contents to generate biogas via anaerobic digestion. However, biogas production is unstable during low crop season. Therefore, this research focuses on improving the biogas generation by adopting the co-digestion method which treats POME and Decanter cake (DC) simultaneously. Results show that DC:POME ratio of 0.8:1 (in term of volatile solids (VS)) with organic loading of 11 g VS/L and HRT of 28 days generated the highest methane yield of 0.515 L CH4/g VS, which is a 186% improvement as compared to mono-digestion of POME. The co-digestion of substrates has shown good biodegradability of organic contents where up to 99.42% chemical oxygen demand (COD) and VS removal efficiencies were attained. Logistic Function Model (LFM) is the most suitable model to predict the performance of co-digestion with the highest R2 of 0.9810.

Microbial fuel cell (MFC) technology has attracted a great amount of attention due to its potential for organic and inorganic waste treatment concomitant with power generation. It is thus seen as a clean energy alternative. Modifications and innovations have been conducted on standalone and hybrid/coupled MFC systems to improve the power output to meet the end goal, namely, commercialization and implementation into existing wastewater treatment plants. As the energy generated is inversely proportional to the size of the reactor, the stacking method has been proven to boost the power output from MFC. In recent years, stacked or scale-up MFCs have also been used as a power source to provide off-grid energy, as well as for in situ assessments. These scale-up studies, however, encountered various challenges, such as cell voltage reversal. This review paper explores recent scale-up studies, identifies trends and challenges, and provides a framework for current and future research.

Three main parameters of palm oil mill effluent (POME) i.e. biological oxygen demand (BOD), total suspended solids (TSS) and oil and grease (O&G), at high concentrations, have hindered efficient anaerobic digestion (AD) due to sludge flotation and scum formation. In this study, Moringa Oleifera extract was co-digested with POME to allow TSS and O&G to be coagulated and settled, and hence, an immobilisation media formed for better digestibility. Mono-digestion (POME, T1 and M. oleifera extract, T2, separately) served as control while co-digestion involved dosing 50 mL of M. oleifera extract (500 mg/L) into a fixed volume of POME (450 mL) at two feeding modes: daily, day 1 to day 30 (T3) and one-time, day 1 (T4). Treatments T1-T4 were conducted in an enclosed AD system for 30 days and the undesirable organic materials removal efficiencies i.e. BODremoval, TSSremoval and O&Gremoval were compared. POME co-digestion, T4, showed an improved 92% TSSremoval, 94% BODremoval and methane yield of 24.3 mL CH4/g COD removed. The results suggested that the nitrogen-fixing capabilities of anoxic microbial cells enhanced proliferation and growth encapsulated within the immobilisation media. Methanogen bacterial DNAs isolated from POME, granular sludge and anaerobically-treated POME were identified as Methanoculleus spp., Methanolinea spp. and Methanoculleus spp., respectively. Two-step complementary DNA (cDNA) and quantitative polymerase chain reaction (qPCR) confirmed the highest methanogen DNA concentration in T4. Therefore, the naturally occurring underutilised M. oleifera can be an organic coagulant for efficient POME co-digestion with an overall 69% and 59.5% higher methane yield and TSSremoval than mono-digestion.

Palm oil mill effluent (POME) is the primary source of water pollution in the oil palm industry. Most palm oil mills are employing a series of anaerobic and aerobic ponds for POME treatment, in order to comply with environmental regulation. In recent years, some mills are installed with biogas capture facilities in order to reduce the emission of greenhouse gas, as well as to raise some profits. In this work, a covered lagoon process for POME treatment, coupled with biogas production was modelled using commercial process simulation software SuperPro Designer v9.0. The simulation results revealed that 29 m3 of biogas can be produced per tonne of treated POME, with a removal efficiency of 92 % for its chemical oxygen demand (COD). Cost analysis has proven that the process is economically viable, with a net present values of $ 2,830,000, IRR of 14.3 %, and payback time of 4.66 years. Process optimisation revealed that the optimal recycle ratio of sludge should be set to 30 %, where the minimum net expenditure ($11,812/y) is achieved, with final effluent COD content of 18 ppm. Note that this takes into consideration of the trade-off between capital and operating costs.

Palm oil mill effluent has been extensively researched via three different technologies, namely chemical, physicochemical and biological treatment methods. Biological treatment by anaerobic and aerobic means is currently the most commonly used method for palm oil mill effluent. However, the greatest challenge posed by them is the inconsistent biological oxygen demand of 20 mg/L for the final treated effluent. Large amount of investment for additional polishing plant prior to the final discharge has been utilised intentionally to further reduce the biochemical oxygen demand values, but the problem remains unresolved. The performance of current palm oil mill effluent treatment system deployed by the industry was evaluated by comparing two different types of anaerobic treatments: open ponding and covered lagoon systems (with hydraulic and gas mixing). The covered lagoon with hydraulic mixing achieved the highest chemical oxygen demand, total suspended solids, total volatile solids and lignin removal efficiencies of >80% compared to other systems which showed

Oil and grease, carbohydrate, protein, and lignin are the main constituents of high strength wastewaters such as dairy wastewater, cheese whey wastewater, distillery wastewater, pulp and paper mill wastewater, and slaughterhouse wastewaters. These constituents have contributed to various operational problems faced by the high-rate anaerobic bioreactor (HRAB). During the hydrolysis stage of anaerobic digestion (AD), these constituents can be hydrolyzed. Since hydrolysis is known to be the rate-limiting step of AD, the overall AD can be enhanced by improving the hydrolysis stage. This can be done by introducing pretreatment that targets the degradation of these constituents. This review mainly focuses on the biological pretreatment on various high-strength wastewaters by using different types of enzymes namely lipase, amylase, protease, and ligninolytic enzymes which are responsible for catalyzing the degradation of oil and grease, carbohydrate, protein, and lignin respectively. This review provides a summary of enzymatic systems involved in enhancing the hydrolysis stage and consequently improve biogas production. The results show that the use of enzymes improves the biogas production in the range of 7 to 76%. Though these improvements are highly dependent on the operating conditions of pretreatment and the types of substrates. Therefore, the critical parameters that would affect the effectiveness of pretreatment are also discussed. This review paper will serve as a useful piece of information to those industries that face difficulties in treating their high-strength wastewaters for the appropriate process, equipment selection, and design of an anaerobic enzymatic system. However, more intensive studies on the optimum operating conditions of pretreatment in a larger-scale and synergistic effects between enzymes are necessary to make the enzymatic pretreatment economically feasible.

Recently, worldwide researchers have been focusing on exploiting of black soldier fly larval (BSFL) biomass to serve as the feed mediums for farmed animals, including aquaculture farming, in order to assuage the rising demands for protein sources. In this study, yeast was introduced into coconut endosperm waste (CEW) whilst serving as the feeding medium to rear BSFL in simultaneously performed in situ fermentation. It was found that at a 2.5 wt% yeast concentration, the total biomass gained, growth rate and rearing time were improved to 1.145 g, 0.085 g/day and 13.5 days, respectively. In terms of solid waste reduction, the inoculation of yeast over 0.5 wt% in CEW was able to achieve more than 50% overall degradation, with the waste reduction indexes (WRIs) ranging from 0.038 to 0.040 g/day. Disregarding the concentration of yeast introduced, the protein productivity from 20 BSFL was enhanced from only 0.018 g/day (the control) to 0.025 g/day with the presence of yeast at arbitrary concentrations. On the other hand, the larval protein yield was fortified from the control (28%) to a highest value of 35% with the presence of a mere 0.02 wt% yeast concentration. To summarize, the inclusion of a minimal amount of yeast into CEW for in situ fermentation ultimately enhanced the growth of BSFL, as well as its protein yield and productivity.

With the growing volume of palm oil production, palm oil mill effluent (POME) is an inevitable by-product that causes serious environmental hazards if discharged directly to the environment. This is mainly due to its high concentrations of chemical oxygen demand (COD) and biochemical oxygen demand (BOD). Note however that, with its high organic content, POME is a great source for biogas production. Therefore, POME pollution abatement coupled with biogas capture and utilisation are vital in order to promote sustainable development goal for the palm oil industry. Conventionally, POME is treated by employing open ponding system without capturing biogas released from the anaerobic process. This treatment system is inefficient, requires large footprint, long hydraulic retention time (HRT) and is unable to consistently comply with the proposed stringent BOD regulatory limit of 20 mg/L to be imposed by Department of Environment (DOE). Hence, the current POME treatment trend is gearing towards biogas capture technology and integrated POME treatment system with the ultimate aim of achieving zero discharge concept in the palm oil mill. This can be achieved by integrating several bioprocesses, with the aim to transform POME into value-added products. This chapter will discuss the current POME treatment and biogas capture technologies, as well as to identify issues and challenges faced by the palm oil miller which deters the development of biogas plants in the mill. Development of biogas from POME will no doubt contribute substantially in Malaysia’s renewable energy sector in the near future.

An optimization study on the mesophilic anaerobic treatment of palm oil mill effluent (POME) in an up-flow anaerobic sludge blanket–hollow centered packed bed (UASB–HCPB) reactor was conducted for the first time by using kinetics modeling. Monod model was opted for the optimization due to its capability of describing the anaerobic digestion and the involvement of adequate amount of parameters in the kinetics model. The best-fit kinetic constants obtained from previous work were incorporated in the optimization model. Fuzzy optimization was adopted and it yielded the optimized chemical oxygen demand (COD) removal of 86.7% and volumetric methane production rate of 0.448 LCH 4 /L.day at hydraulic retention time (HRT) of 4.33 days, organic loading rate (OLR) of 14.75 gCOD/L.day and mixed liquor volatile suspended solid (MLVSS) concentration of 19,130 mg/L. A confirmative experiment was conducted and the results validate the legitimacy of the fuzzy optimization model. Further studies are required to improve the reliability of this newly introduced optimization technique in the wastewater treatment industry.

Optimization of an integrated anaerobic-aerobic bioreactor (IAAB) treatment system for the reduction of organic matter (Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD) and Total Suspended Solids (TSS) concentrations) in Palm Oil Mill Effluent (POME) to legal standards with high methane yield was performed for the first time under thermophilic condition (50°C–55°C) by using response surface methodology (RSM). The experiments were conducted based on a central composite rotatable design (CCRD) with three independent operating variables, organic loading rates in anaerobic compartment (OLRan) and mixed liquor volatile suspended solids (MLVSS) concentration in anaerobic (MLVSSan) and aerobic compartments (MLVSSa). The optimum conditions for the POME treatment were determined as OLRan of 15.6 g COD·L−1·d−1, MLVSSan of 43100 mg·L−1, and MLVSSa of 18600 mg·L−1, where high aerobic COD, BOD and TSS removal efficiencies of 96.3%, 97.9%, and 98.5% were achieved with treated BOD of 56 mg·L−1 and TSS of 28 mg·L−1 meeting the discharge standard. This optimization study successfully achieved a reduction of 42% in the BOD concentrations of the final treated effluent at a 48% higher OLRan as compared to the previous works. Besides, thermophilic IAAB system scores better feasibility and higher effectiveness as compared to the optimized mesophilic system. This is due to its higher ability to handle high OLR with higher overall treatment efficiencies (more than 99.6%), methane yield (0.31 L CH4·g−1 CODremoved) and purity of methane (67.5%). Hence, these advantages ascertain the applicability of thermophilic IAAB in the POME treatment or even in other high-strength wastewaters treatment.

This work presents the evaluation of biokinetic coefficients for a novel integrated anaerobic-aerobic bioreactor (IAAB) at different organic loading rates (OLRs) (10.5-22.5 g COD/L per day) treating palm oil mill effluent. The overall efficiencies of the chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were more than 99% for OLR up to 19.5 g COD/L day with biogas production containing 48-64% of methane. The effluent quality remained stable (BOD 80 mg/L) and satisfied with the discharge limit. Stover-Kincannon model was the most appropriate model to estimate the performance of anaerobic compartment of IAAB, while Monod model was best suited for describing the aerobic compartment.BOD: biochemical oxygen demand; COD: chemical oxygen demand; DO: dissolved oxygen; GLSS: gas-liquid-solid separator; MLSS: mixed liquor suspended solid; MLVSS: mixed liquor volatile suspended solid; POME: palm oil mill effluent; RAS: returned activated sludge; SBR: sequencing batch reactor; SVI: sludge volume index; TA: total alkalinity; TN: total nitrogen; TS: total solids; TSS: total suspended solids; UASB: upflow anaerobic sludge blanket; UASFF: upflow anaerobic sludge blanket fixed film; VFA: volatile fatty acid; VSS: volatile suspended solids.

Palm oil mill effluent (POME) with average chemical oxygen demand (COD) and biochemical oxygen demand (BOD) of 70,000 and 30,000 mg/L, respectively, can cause serious environmental hazards if discharged untreated. There are conventional palm oil mill effluent (POME) treatment systems that require large footprint, long HRT and fail to meet the Malaysian Department of Environment (DOE) discharge limit. Hence, the current research is aimed to design a novel integrated anaerobic–aerobic bioreactor (IAAB) for POME treatment in order to overcome these shortcomings of the conventional system. IAAB is a new bioreactor configuration which integrates anaerobic and aerobic digestion in one reactor. The overall removal efficiencies in steady state condition in terms of chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total suspended solids (TSS) were more than 99% at the organic loading rate (OLR) of 10.5 g COD/L day with methane yield of 0.24 L CH4/g COD removed. The effluent quality remained stable (BOD < 70 mg/L) and complied with the discharge limit (BOD < 100 mg/L). Overall, the IAAB system exhibited good stability and pH adjustment was unnecessary. The results show that the IAAB achieves higher performance in terms of organic removal efficiency and methane yield at higher OLR and shorter HRT as compared to the conventional system. Further evaluations of its long-term performance are proposed for the subsequent study.

This research is aimed at improving the thermophilic aerobic treatment system of anaerobically digested palm oil mill effluent (POME) through optimization of mixed liquor suspended solids (MLSS) at high concentration range for the first time besides other parameters of organic loading rate (OLR), dissolved oxygen (DO) concentrations and settling time. Chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total suspended solids (TSS) removal ratios were measured as indicators of the system performance. Experimental results clearly indicate that MLSS and OLR are the crucial parameters in thermophilic aerobic treatment. Optimal COD, BOD and TSS removals up to 86%, 87% and 89%, respectively, were achieved with MLSS concentration and OLR of 27,000 mg/L and 2.5 g COD/(L day), respectively. More significantly, high MLSS concentration range which is yet to be reported was successfully applied and this has resulted in superior performance as compared to other thermophilic treatment studies. No significant improvement of the treatment efficiency was attained with DO concentration exceeding 5 mg/L and settling time up to 24 h. Hence, operation at DO concentration of 2 mg/L and settling time of 2 h gives a good compromise between effluent quality and system operating costs.

The production of highly polluting palm oil mill effluent (POME) has resulted in serious environmental hazards. While anaerobic digestion is widely accepted as an effective method for the treatment of POME, anaerobic treatment of POME alone has difficulty meeting discharge limits due to the high organic strength of POME. Hence, subsequent post-treatment following aerobic treatment is vital to meet the discharge limits. The objective of the present study is to investigate the aerobic treatment of anaerobically digested POME by using a sequencing batch reactor (SBR). The SBR performance was assessed by measuring Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD) and Total Suspended Solids (TSS) removal as well as Sludge Volume Index (SVI). The operating pH and dissolved oxygen concentrations were found to be 8.25-9.14 and 1.5-6.4 mg/L, respectively, throughout the experiment. The experimental results demonstrate that MLVSS, OLR and sludge loading rate (SLR) play a significant role in the organic removal efficiency of SBR systems and therefore, further investigation on these parameters was conducted to attain optimum SBR performance. Maximum COD (95-96%), BOD (97-98%) and TSS (98-99%) removal efficiencies were achieved at optimum OLR, SLR and MLVSS concentration ranges of 1.8-4.2 kg COD/m(3)day, 2.5-4.6 kg TSS/m(3)day and 22,000-25,000 mg/L, respectively. The effluent quality remained stable and complied with the discharge limit. At the same time, the sludge showed good settling properties with average SVI of 65. It is envisaged that the SBR process could complement the anaerobic treatment to produce final treated effluent which meets the discharge limit.

Aerobic treatment of wastewater under thermophilic conditions has received growing interest in recent years. Because of the high discharge temperature (75 to 85 °C) of palm oil mill effluent (POME), it would be more economical if POME were treated thermophilically, as then cooling facilities prior to biological treatment can be eliminated. In the present investigation, the feasibility of thermophilic aerobic biological treatment as a suitable post-treatment system for anaerobically treated POME was examined. Also, the effects of temperature on the treated effluent quality were investigated by using sequencing batch reactors (SBRs) under mesophilic (28 °C) and thermophilic (45, 50, and 55 °C) conditions. The average total COD (TCOD) removal efficiencies varied from 55 to 98% at organic loading rates (OLR) of 2.6 to 4.5 kg COD/m3·day, dissolved oxygen (DO) concentrations of 2.9−4.5 mg/L, and mixed-liquor suspended solids (MLSS) concentrations of 22500−24200 mg/L. The results show that the thermophilic aerob...

Thermophilic treatment of palm oil mill effluent (POME) was studied in a novel integrated anaerobic-aerobic bioreactor (IAAB). The IAAB was subjected to a program of steady-state operation over a range of organic loading rate (OLR)s, up to 30 g COD/L day in order to evaluate its treatment capacity. The thermophilic IAAB achieved high chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total suspended solids (TSS) removal efficiencies of more than 99% for OLR up to 18.5 g COD/L day. High methane yield of 0.32 LCH(4) (STP)/g COD(removed) with compliance of the final treated effluent to the discharge limit were achieved. This is higher than that of the mesophilic system due to the higher maximum specific growth rate (μ(max)) of the thermophilic microorganisms. Besides, coupling the model of Grau second order model (anaerobic system) with the model of Monod (aerobic system) will completely define the IAAB system.