Anaerobically-treated palm oil mill effluent (POME) still has unacceptable properties for water recycling and reuse, with an unpleasant appearance due to the brownish color caused by tannins and phenolic compounds. This study proposes an approach for treating anaerobically-treated POME for water recycling by combining organic precipitation, electrocoagulation (EC), and ion-exchange resin, followed by reverse osmosis (RO) membrane filtration in series. The results indicated that the organic precipitation enhanced the efficiency of EC treatment in reducing the concentrations of tannins, color, and chemical oxygen demand (COD) of the anaerobically-treated POME effluent, with reductions of 95.73%, 96.31%, and 93.96% for tannin, color, and COD, respectively. Moreover, organic precipitation affected the effectiveness of Ca2+ and Mg2+ ion removal using ion exchange resin and RO membrane filtration. Without prior organic precipitation, the ion-exchange resin process required a longer contact time, and the RO membrane filtration treatment was hardly effective in removing total dissolved solids (TDS). The combined process gave a water quality that meets the criteria set by the Thailand Ministry of Industry for industrial boiler use (COD 88 mg/L, TDS <0.001 mg/L, water hardness <5 mg-CaCO3/L, and pH 6.9).

The escalating consumer demand for crabs results in a growing amount of waste, including shells, claws, and other non-edible parts. The resulting crab shell waste (CSW) is disposed of via incineration or landfills which causes environmental pollution. CSW represents a potential biological resource that can be transformed into valuable resources via pyrolysis technique. In this study, microwave pyrolysis of CSW using self-purging, vacuum, and steam activation techniques was examined to determine the biochar production yield and its performance in treating palm oil mill effluent (POME). The biochar produced through microwave pyrolysis exhibits yields ranging from 50 to 61 wt%, showing a hard texture, low volatile matter content (≤34.1 wt%), and high fixed carbon content (≥58.3 wt%). The KOH-activated biochar demonstrated a surface area of up to 177 m2/g that is predominantly composed of mesopores, providing a good amount of adsorption sites for use as adsorbent. The biochar activated with steam removed 8.3 mg/g of BOD and 42 mg/g of COD from POME. The results demonstrate that microwave pyrolysis of CSW is a promising technology to produce high-quality biochar as an adsorbent for POME treatment.

Attributable to the prosperous production growth of palm oil in Malaysia, the generated palm oil mill effluent (POME) poses a high threat owing to its highly polluted characteristic. Urged by the escalating concern of environmental conservation, POME pollution abatement and potential energy recovery from the effluent are flagged up as a research topic of interest. In this study, a cutting-edge photocatalytic fuel cell (PFC) system with employment of ZnO/Zn nanorod array (NRA) photoanode, CuO/Cu cathode, and persulfate (PS) oxidant was successfully designed to improve the treatment of POME and simultaneous energy production. The photoelectrodes were fabricated and characterized by field emission scanning electron microscopy with energy (FESEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and Brunauer, Emmett, and Teller analysis (BET). Owing to the properties of strong oxidant of PS, the proposed PFC/PS system has exhibited exceptional performance, attaining chemical oxygen demand (COD) removal efficiency of 96.2%, open circuit voltage (Voc) of 740.0 mV, short circuit current density (Jsc) of 146.7 μA cm-2, and power density (Pmax) of 35.6 μW cm-2. The pre-eminent PFC/PS system performance was yielded under optimal conditions of 2.5 mM of persulfate oxidant, POME dilution factor of 1:20, and natural solution pH of 8.51. Subsequently, the postulated photoelectrocatalytic POME treatment mechanism was elucidated by the radical scavenging study and Mott-Schottky (M-S) analysis. The following recycling test affirmed the stability and durability of the photoanode after four continuous repetition usages while the assessed electrical energy efficiency revealed the economic viability of PFC system serving as a post-treatment for abatement of POME. These findings contributed toward enhancing the sustainability criteria and economic viability of palm oil by adopting sustainable and efficient POME post-treatment technology.

Residual oil in palm oil mill effluent (POME) poses difficulties in its treatment chain. Non-ionic surfactants containing different hydrophobic tail structures and their optimal concentrations were evaluated for effectiveness in biohydrogen production. By adding the surfactants at their critical micelle concentration in synthetic oily wastewater, the maximal H2 yield was increased by 2.2 and 3.5 times for Triton X-100 and Tergitol 15-S-9, respectively, compared to the control. Using real POME, the supplemental Tergitol 15-S-9 resulted in a 56.4 % improvement in H2 production. For continuous digestion studies, pure POME and Tergitol 15-S-9 supplemented POME (sPOME) were fed to thermophilic anaerobic sequencing batch reactors (ASBRs) under hydraulic retention time (HRT) of 32-12.5 days. Optimally at HRT 19 days, H2 content in the biogas from sPOME-fed ASBR was noticeably higher, which gave a superior yield of 203.4 mLH2/gCODremoved (+15 %).

Safe disposal of effluent from palm oil production poses an environmental concern. The highly polluting effluent is customarily treated by unsustainable open ponds with low efficiency, direct emissions, and massive land use. This study looks into an application of integrated anaerobic/oxic/oxic scheme for treatment of high strength palm oil mill effluent. The anaerobic reactors functioned as a prime degrader that removed up to 97.5% of the chemical oxygen demand (COD), while the aerobic reactors played a role of an effluent polisher that further reduced the COD. Their complementing roles resulted in a remarkable removal of 99.7%. Assessment of emission mitigation and biogas energy revealed that yearly energy of 53.2 TJ, emissions reduction of 239,237 tCO2 and revenue of USD 1.40 millions can be generated out of electricity generation and heating. The integrated scheme provides a viable and sustainable treatment of the high strength palm oil mill effluent.

Anaerobic codigestion (AcD) of agroindustrial residues was investigated. Granular sludge from bench-scale bioreactors digesting different manure were acclimated and recycled as microbial seed sludge to demonstrate inoculum-type influence on digestion performance. The biomethane potential (BMP) assay was operated for 30 days at 40 ± 2 °C in batch-type laboratory-scale reactors (100 mL). In inoculum amended reactors, codigestion showed significant, yet distinctive, biomethanation than monodigestion with a 5-fold increase (p < 0.05) in average biogas (248.3 ± 5.30 mL gVS-1) and CH4 yield (207.5 ± 4.15 mL gVS-1). The pH, soluble chemical oxygen demand (sCOD) and volatile fatty acids (VFAs) concentrations were within limits for stable AcD process with elevated total solids (TS) and volatile solids (VS) removal efficiencies. This study reinforces advancements in the recycling of digestate in biodigesters and suggests the appropriate selection of inoculum, preferably cow manure, to essentially boost methane production from these wastes.

In predicting palm oil mill effluent (POME) degradation efficiency, previous developed quadratic model quantitatively evaluated the effects of O2 flowrate, TiO2 loadings and initial concentration of POME in labscale photocatalytic system, which however suffered from low generalization due to the overfitting behaviour. Evidently, high RMSE (131.61) and low R2 (-630.49) obtained indicates its insufficiency in describing POME degradation at unseen factor ranges, hence verified the fact of poor generalization. To overcome this issue, several models were developed via machine learning-assisted techniques, namely Gaussian Process Regression (GPR), Linear Regression (LR), Decision Tree (DT), Supported Vector Machine (SVM) and Regression Tree Ensemble (RTE), subsequently being assessed systematically. To achieve high generalization, all models were subjected to \'train-all-test-all\' strategy, 5-fold and 10-fold cross validation. Specifically, GPR model was furnished with high accuracy in \'train-all-test-all\' strategy, judging from its low RMSE (1.0394) and high R2 (0.9962), which however menaced by the risk of overfitting. In contrast, despite relatively poorer RMSE and R2 (1.7964 and 0.9886) obtained in 5-fold cross validation, GPR model was rendered with highest generalization, while sufficiently preserving its accuracy in development process. Besides, SVM and RTE models were also demonstrated promising R2 (0.9372 and 0.9208), which however shadowed by their high RMSEs (4.2174 and 4.7366). Furthermore, the extraordinary generalization of GPR model was coincidentally verified in 10-fold cross validation. The lowest RMSE (2.1624) and highest R2 (0.9835) obtained with feature number of 36 asserted its sufficiency in both generalization and accuracy prospect. Other models were all rendered with slight lower R2 (> 0.9), plausibly due to the higher RMSE (> 4.0). According to GPR model, optimized POME degradation (52.52%) can be obtained at 70 mL/min of O2, 70.0 g/L of TiO2 and 250 ppm of POME concentration, with only ∼3% error as compared to the actual data.

In this study, carbon-silica based acid catalysts derived from rice husks (RH) were successfully synthesised using microwave (MW) technology. The results showed that MW sulphonation produced Sulphur (S) content of 17.2-18.5 times higher than in raw RH. Fourier-transform Infrared Spectroscopy (FTIR) showed peak at 1035 cm-1 which corresponded to O˭S˭O stretching of sulphonic (-SO3H) group. XRD showed sulfonated RH catalysts (SRHCs) have amorphous structure, and through SEM, broadening of the RH voids and also formation of pores is observed. RH600 had the highest surface area of 14.52 m2/g. SRHCs showed high catalytic activity for esterification of oleic acid with methanol with RH600 had the highest initial formation rate (6.33 mmolL-1min-1) and yield (97%). The reusability of the catalyst showed gradually dropped yield of product for every recycle, which might be due to leaching of -SO3H. Finally, esterification of oil recovered from palm oil mill effluent (POME) with methanol achieved a conversion of 87.3% free fatty acids (FFA) into fatty acid methyl esters (FAME).

Chlorella sorokiniana CY-1 was cultivated using palm oil mill effluent (POME) in a novel-designed photobioreactor (NPBR) and glass-made vessel photobioreactor (PBR). The comparison was made on biomass and lipid productions, as well as its pollutants removal efficiencies. NPBR is transparent and is developed in thin flat panels with a high surface area per volume ratio. It is equipped with microbubbling and baffles retention, ensuring effective light and CO2 utilization. The triangular shape of this reactor at the bottom serves to ease microalgae cell harvesting by sedimentation. Both biomass and lipid yields attained in NPBR were 2.3-2.9 folds higher than cultivated in PBR. The pollutants removal efficiencies achieved were 93.7% of chemical oxygen demand, 98.6% of total nitrogen and 96.0% of total phosphorus. Mathematical model revealed that effective light received and initial mass contributes toward successful microalgae cultivation. Overall, the results revealed the potential of NPBR integration in Chlorella sorokiniana CY-1 cultivation, with an aim to achieve greater feasibility in microalgal-based biofuel real application and for environmental sustainability.

The present study reports mathematical modelling of palm oil mill effluent and palm-pressed fiber mixtures (0% to 100%) during vermicomposting process. The effects of different mixtures with respect to pH, C:N ratio and earthworms have been optimized using the modelling parameters. The results of analysis of variance have established effect of different mixtures of palm oil mill effluent plus palm press fiber and time, under selected physicochemical responses (pH, C:N ratio and earthworm numbers). Among all mixtures, 60% mixture was achieved optimal growth at pH 7.1 using 16.29 C:N ratio in 15 days of vermicomposting. The relationship between responses, time and different palm oil mill waste mixtures have been summarized in terms of regression models. The obtained results of mathematical modeling suggest that these findings have potential to serve a platform for further studies in terms of kinetic behavior and degradation of the biowastes via vermicomposting.