Microbial granules on reactors performance during organic butyrate digestion: clean production

This critical review for anaerobic degradation of complex organic compounds like butyrate using reactors has been enormously applied for biogas production. Biogas production rate has a great impact on: reactor granulation methanogenesis, nutrient content, shear velocity, organic loading and loss of nutrients taking place in the reactor continuously. Various technologies have been applied to closed anaerobic reactors to improve biogas production and treatment efficiency. Recent reviews showed that the application of closed anaerobic reactors can accelerate the degradation of organics like volatile fatty acid-butyrate and affect microbial biofilm formation by increasing the number of methanogens and increase methane production 16.5 L-1 CH4 L-1 POME-1. The closed anaerobic reactors with stable microbial biofilm and established organic load were responsible for the improvement of the reactor and methane production. The technology mentioned in this review can be used to monitor biogas concentration, which directly correlates to organic concentrations. This review attempts to evaluate interactions among the: degradation of organics, closed anaerobic reactors system, and microbial granules. This article provides a useful picture for the improvement of the degradation of organic butyrate for COD removal, biogas and methane production in an anaerobic closed reactor.

Insights into bacterial community metatranscriptome and metabolome in river water influenced by palm oil mill effluent final discharge

AIMS

This study aimed to investigate the effect of palm oil mill effluent (POME) final discharge on the active bacterial composition, gene expression, and metabolite profiles in the receiving rivers to establish a foundation for identifying potential biomarkers for monitoring POME pollution in rivers.

METHODS AND RESULTS

The POME final discharge, upstream (unpolluted by POME), and downstream (effluent receiving point) parts of the rivers from two sites were physicochemically characterized. The taxonomic and gene profiles were then evaluated using de novo metatranscriptomics, while the metabolites were detected using qualitative metabolomics. A similar bacterial community structure in the POME final discharge samples from both sites was recorded, but their composition varied. Redundancy analysis showed that several families, particularly Comamonadaceae and Burkholderiaceae [Pr(>F) = 0.028], were positively correlated with biochemical oxygen demand (BOD5) and chemical oxygen demand (COD). The results also showed significant enrichment of genes regulating various metabolisms in the POME-receiving rivers, with methane, carbon fixation pathway, and amino acids among the predominant metabolisms identified (FDR < 0.05, PostFC > 4, and PPDE > 0.95). This was further validated through qualitative metabolomics, whereby amino acids were detected as the predominant metabolites.

CONCLUSIONS

The results suggest that genes regulating amino acid metabolism have significant potential for developing effective biomonitoring and bioremediation strategies in river water influenced by POME final discharge, fostering a sustainable palm oil industry.

Reversal of Neuralgia Effect of Beta Carotene in Streptozotocin-Associated Diabetic Neuropathic Pain in Female Zebrafish via Matrix Metalloprotease-13 Inhibition

Beta carotene is a natural anti-oxidant agent, and it inhibits the matrix metalloprotease (MMP) activity. Diabetic neuropathic pain (DNP) is produced by cellular oxidative stress. The role of the beta carotene effect in diabetic neuropathic pain is not explored yet. The present study is designed for the evaluation of the palm oil mill effluent-derived beta carotene (PBC) effect in DNP in zebrafish. The DNP was induced by the intraperitoneal administration of streptozotocin (STZ). Blood glucose levels of above 15 mM were considered to be diabetic conditions. The zebrafish were exposed to test compound PBC (25, 50, and 100 µM), pregabalin (PG: 10 μM), and an MMP-13 inhibitor (CL-82198; 10 μM) for 10 consecutive days from day 11. The neuralgic behavioral parameters, i.e., temperature test, acetic acid test, and fin clip test were assessed on day 0 and the 7th, 14th, and 21st days. On the 22nd day, the blood glucose and MMP-13 levels and brain thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), and MMP-13 activity levels were estimated. The treatment of PBC ameliorated the DNP-associated behavioral and biochemical changes. The results are similar to those of PG and CL-82198 treatments. Hence, the PBC possesses a potentially ameliorative effect against DNP due to its potential anti-oxidant, anti-lipid peroxidation, and MMP-13 inhibitory actions.

Evaluation of potential feedstock for biogas production via anaerobic digestion in Malaysia: kinetic studies and economics analysis

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.

Recent Developments in Biological Processing Technology for Palm Oil Mill Effluent Treatment-A Review

Simple Summary

Palm oil mill effluent (POME) requires treatment prior to discharge to the environment. Biological processing technology is highly preferable due to its advantages of environmentally friendliness, cost effectiveness, and practicality. These methods utilized various designs and modifications of bioreactors fostering effective fermentation technology in the presence of fungi, bacteria, microalgae, and a consortium of microorganisms. This review highlights the recent biological processing technology for POME treatment as a resource utilization.

Abstract

POME is the most voluminous waste generated from palm oil milling activities. The discharge of POME into the environment without any treatment processing could inflict an undesirable hazard to humans and the environment due to its high amount of toxins, organic, and inorganic materials. The treatment of POME prior to discharge into the environment is utmost required to protect the liability for human health and the environment. Biological treatments are preferable due to eco-friendly attributes that are technically and economically feasible. The goal of this review article is to highlight the current state of development in the biological processing technologies for POME treatment. These biological processing technologies are conducted in the presence of fungi, bacteria, microalgae, and a consortium of microorganisms. Numerous microbes are listed to identify the most efficient strain by monitoring the BOD, COD, working volume of the reactor, and treatment time. The most effective processing technology for POME treatment uses an upflow anaerobic sludge blanket reactor with the COD value of 99%, hydraulic retention time of 7.2 days, and a working volume of 4.7 litres. Biological processing technologies are mooted as an efficient and sustainable management practice of POME waste.

Life Cycle Assessment of an Integrated Membrane Treatment System of Anaerobic-Treated Palm Oil Mill Effluent (POME)

A life cycle assessment of anaerobic-treated palm oil mill effluent (POME) was conducted to assess the environmental performance on two integrated treatment processes: the typical hollow fiber membrane ultrafiltration module coupled with adsorption and electro-oxidation as pretreatment. The analysis was undertaken using the ReCiPe 2016 method and SimaPro v9 software was employed using a ‘cradle-to-gate’ approach. The results showed that hollow fiber membrane from the adsorption integrated membrane impacted significantly at 42% to 99% across all impact categories for both processes. Overall, the electro-oxidation integrated membrane was discovered to have a lesser environmental impact, particularly on the ozone formation (human health) (HOFP) at 0.38 kg NOx-eq in comparison to the adsorption integrated membrane at 0.66 kg NOx-eq. The total characterization factor of the endpoint category for human health is 8.61 × 10⁻⁴ DALY (adsorption integrated membrane) and 8.45 × 10⁻⁴ DALY (electro-oxidation integrated membrane). As membrane treatment is closely linked to energy consumption, the environmental impact with different sources of energy was evaluated for both processes with the impacts decreasing in the following order: Grid > Biogas > Grid/Solar. Future research should concentrate on determining the overall ‘cradle-to-grave’ environmental impact of treating POME, as well as other scenarios involving membrane treatment energy utilization using LCA. This study can help decision-makers in identifying an environmentally sustainable POME treatment and management, especially in Malaysia.

Dairy manure pellets and palm oil mill effluent as alternative nutrient sources in cultivating Sporosarcina pasteurii for calcium carbonate bioprecipitation

Microbially induced carbonate precipitation (MICP) is a process that hydrolysis urea by microbial urease to fill the pore spaces of soil with induced calcium carbonate (CaCO₃ ) precipitates, which eventually results in improved or solidified soil. This research explored the possibility of using dairy manure pellets (DMP) and palm oil mill effluent (POME) as alternative nutrient sources for Sporosarcina pasteurii cultivation and CaCO₃ bioprecipitation. Different concentrations (20 to 80 g l^-1 ) of DMP and POME were used to propagate the cells of Sporosarcina pasteurii under laboratory conditions. The measured CaCO₃ contents for MICP soil specimens that were treated with bacterial cultures grown in DMP medium (60%, w/v) was 15.30 ±0.04g ml^-1 and POME medium (40%, v/v) was 15.49 ±0.05g ml^-1 after 21 days curing. The scanning electron microscopy showed that soil treated with DMP had rhombohedral structure-like crystals with smooth surfaces, while that of POME entailed ring-like cubical formation with rough surfaces Electron dispersive X-ray analysis was able to identify a high mass percentage of chemical element compositions (Ca, C, and O), while spectrum from Fourier-transform infrared spectroscopy confirmed the vibration peak intensities for CaCO₃ . Atomic force microscopy further showed clear topographical differences on the crystal surface structures that were formed around the MICP treated soil samples. These nutrient sources (DMP and POME) showed encouraging potential cultivation mediums to address high costs related to bacterial cultivation and biocementation treatment.

Highly Effective Cow Bone Based Biocomposite for the Sequestration of Organic Pollutant Parameter from Palm Oil Mill Effluent in a Fixed Bed Column Adsorption System

The reduction of chemical oxygen demand (COD) from palm oil mill effluent (POME) is very significant to ensure aquatic protection and the environment. Continuous adsorption of COD in a fixed bed column can be an effective treatment process for its reduction prior to discharge. Adsorption capacity of bone derived biocomposite synthesized from fresh cow bones, zeolite, and coconut shells for the reduction in the organic pollutant parameter was investigated in this study in a fixed bed column. The effect of influent flow rate (1.4, 2.0, and 2.6 mL/min) was determined at an influent pH 7. The optimum bed capacity on the fabricated composite of surface area of 251.9669 m²/g was obtained at 1.4 mL/min at breakthrough time of 5.15 h influent POME concentration. The experimental data were fitted to Thomas, Adams–Bohart, and Yoon–Nelson models fixed bed adsorption models. It was revealed that the results fitted well to the Adams Bohart model with a correlation coefficient of R² > 0.96 at different influent concentration. Adsorption rate constant was observed to increase at lower flow rate influent concentration, resulting in longer empty bed contact time (EBCT) for the mass transfer zone of the column to reach the outlet of the effluent concentration. In general, the overall kinetics of adsorption indicated that the reduction in COD from POME using a bone-biocomposite was effective at the initial stage of adsorption. The pore diffusion model better described the breakthrough characteristics for COD reduction with high correlation coefficient. Shorter breakthrough time compared to EBCT before regeneration indicated that the bone composite was suitable and effective for the reduction in COD from POME using fixed bed column adsorption.

Utilization of palm oil mill effluent as a novel substrate for the production of antifungal compounds by Streptomyces philanthi RM-1-138 and evaluation of its efficacy in suppression of three strains of oil palm pathogen

AIMS

This study aimed to use palm oil mill effluent (POME) as a renewable resource for the production of antifungal compounds by Streptomyces philanthi RM-1-138 against Ganoderma boninense, Ceratocystis paradoxa and Curvularia oryzae.

METHODS AND RESULTS

The efficacy of antifungal compounds RM-1-138 against the three strains of fungal oil palm pathogen was evaluated both in vitro and on oil palm leaf segments. In vitro studies using confrontation tests on glucose yeast-malt extract (GYM) agar plates indicated that the strain RM-1-138 inhibited the growth of all three fungal pathogenic strains. The antifungal compounds produced in the GYM medium exhibited significantly higher inhibition (79%-100%) against the three fungal pathogens than using the diluted POME (50%) medium (80%-83% inhibition). The optimum condition for the production of antifungal compounds from the strain RM-1-138 was as following: POME of 47,966 mg L^-1 chemical oxygen demand (COD), the initial pH at 7.0 and supplemented with yeast extract (0.4%). Meanwhile, severe morphological and internal abnormalities in C. oryzae hyphae were observed under a scanning electron microscope and transmission electron microscope. In vivo experiment on oil palm leaf segments indicated that the efficacy of the antifungal compounds RM-1-138 (DSI = 1.3) were not significantly difference in the suppression of Curvularia leaf spot compared with the two commercial chemical fungicides of mancozeb^® (DSI = 1.0) and tetraconazole^® (DSI = 1.3).

CONCLUSIONS

Antifungal compounds produced by S. philanthi RM-1-138 grown in POME have the potential to inhibit fungal pathogens.

SIGNIFICANCE AND IMPACT OF THE STUDY

The POME (about 47 mg L^-1 COD) with the initial pH of 7.0 and supplementation of 0.4% nitrogen could be used as a culture medium for the growth and production of antifungal compounds of S. philanthi RL-1-138. In addition, the antifungal compound RM-1-138 could suppress the three strains of oil palm fungal pathogen tested on oil palm leaf segment.

Evaluating Fertilizer-Drawn Forward Osmosis Performance in Treating Anaerobic Palm Oil Mill Effluent

Fertilizer-drawn forward osmosis (FDFO) is a potential alternative to recover and reuse water and nutrients from agricultural wastewater, such as palm oil mill effluent that consists of 95% water and is rich in nutrients. This study investigated the potential of commercial fertilizers as draw solution (DS) in FDFO to treat anaerobic palm oil mill effluent (An-POME). The process parameters affecting FO were studied and optimized, which were then applied to fertilizer selection based on FO performance and fouling propensity. Six commonly used fertilizers were screened and assessed in terms of pure water flux (J_w) and reverse salt flux (J_S). Ammonium sulfate ((NH₄)₂SO₄), mono-ammonium phosphate (MAP), and potassium chloride (KCl) were further evaluated with An-POME. MAP showed the best performance against An-POME, with a high average water flux, low flux decline, the highest performance ratio (PR), and highest water recovery of 5.9% for a 4-h operation. In a 24-h fouling run, the average flux decline and water recovered were 84% and 15%, respectively. Both hydraulic flushing and osmotic backwashing cleaning were able to effectively restore the water flux. The results demonstrated that FDFO using commercial fertilizers has the potential for the treatment of An-POME for water recovery. Nevertheless, further investigation is needed to address challenges such as J_S and the dilution factor of DS for direct use of fertigation.

Recycling anaerobic digestate enhances the co-digestion potential of agro-industrial residues: influence of different digestates as sources of microbial inoculum

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.

Upcycling the Spent Mushroom Substrate of the Grey Oyster Mushroom Pleurotus pulmonarius as a Source of Lignocellulolytic Enzymes for Palm Oil Mill Effluent Hydrolysis

Mushroom cultivation along with the palm oil industry in Malaysia have contributed to large volumes of accumulated lignocellulosic residues that cause serious environmental pollution when these agroresidues are burned. In this study, we illustrated the utilization of lignocellulolytic enzymes from the spent mushroom substrate of Pleurotus pulmonarius for the hydrolysis of palm oil mill effluent (POME). The hydrolysate was used for the production of biohydrogen gas and enzyme assays were carried out to determine the productivities/activities of lignin peroxidase, laccase, xylanase, endoglucanase and β-glucosidase in spent mushroom substrate. Further, the enzyme cocktails were concentrated for the hydrolysis of POME. Central composite design of response surface methodology was performed to examine the effects of enzyme loading, incubation time and pH on the reducing sugar yield. Productivities of the enzymes for xylanase, laccase, endoglucanase, lignin peroxidase and β-glucosidase were 2.3, 4.1, 14.6, 214.1, and 915.4 U g^-1, respectively. A maximum of 3.75 g/l of reducing sugar was obtained under optimized conditions of 15 h incubation time with 10% enzyme loading (v/v) at a pH of 4.8, which was consistent with the predicted reducing sugar concentration (3.76 g/l). The biohydrogen cumulative volume (302.78 ml H₂.L^-1 POME) and 83.52% biohydrogen gas were recorded using batch fermentation which indicated that the enzymes of spent mushroom substrate can be utilized for hydrolysis of POME.

Photocatalytic Technology for Palm Oil Mill Effluent (POME) Wastewater Treatment: Current Progress and Future Perspective

The palm oil industry produces liquid waste called POME (palm oil mill effluent). POME is stated as one of the wastes that are difficult to handle because of its large production and ineffective treatment. It will disturb the ecosystem with a high organic matter content if the waste is disposed directly into the environment. The authorities have established policies and regulations in the POME waste quality standard before being discharged into the environment. However, at this time, there are still many factories in Indonesia that have not been able to meet the standard of POME waste disposal with the existing treatment technology. Currently, the POME treatment system is still using a conventional system known as an open pond system. Although this process can reduce pollutants’ concentration, it will produce much sludge, requiring a large pond area and a long processing time. To overcome the inability of the conventional system to process POME is believed to be a challenge. Extensive effort is being invested in developing alternative technologies for the POME waste treatment to reduce POME waste safely. Several technologies have been studied, such as anaerobic processes, membrane technology, advanced oxidation processes (AOPs), membrane technology, adsorption, steam reforming, and coagulation. Among other things, an AOP, namely photocatalytic technology, has the potential to treat POME waste. This paper provides information on the feasibility of photocatalytic technology for treating POME waste. Although there are some challenges in this technology’s large-scale application, this paper proposes several strategies and directions to overcome these challenges.

Prospective Application of Palm Oil Mill Boiler Ash as a Biosorbent: Effect of Microwave Irradiation and Palm Oil Mill Effluent Decolorization by Adsorption

Common conventional biological treatment methods fail to decolorize palm oil mill effluent (POME). The present study focused on using the abundant palm oil mill boiler (POMB) ashes for POME decolorization. The POMB ashes were subjected to microwave irradiation and chemical treatment using H₂SO₄. The resultant adsorbents were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Brunauer–Emmett–Teller (BET) analyses. The adsorption efficiency was evaluated at various pH levels (2–8.5), adsorption dosages (3–15 g) in 200 mL, and contact times (1–5 h). The microwave-irradiated POMB-retained ash recorded the highest color removal of 92.31%, for which the best conditions were pH 2, 15 g adsorbent dosage in 200 mL, and 5 h of contact time. At these best treatment conditions, the color concentration of the treated effluent was analyzed using the method proposed by the American Dye Manufacturers Institute (ADMI). The color concentration was 19.20 ADMI, which complies with the Malaysia discharge standard class A. The Freundlich isotherm model better fit the experimental data and had a high R² of 0.9740. Based on these results, it can be deduced that microwave-irradiated POMB-retained ash has potential applications for POME decolorization via a biosorption process.

Bio-Optimization of Chemical Parameters and Earthworm Biomass for Efficient Vermicomposting of Different Palm Oil Mill Waste Mixtures

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.

Enhanced biosorption of transition metals by living Chlorella vulgaris immobilized in Ca-alginate beads

In this study freely suspended and Ca-alginate immobilized C. vulgaris cells were used for the biosorption of Fe(II), Mn(II), and Zn(II) ions, from the aqueous solution. Experimental data showed that biosorption capacity of algal cells was strongly dependent on the operational condition such as pH, initial metal ions concentration, dosages, contact time and temperature. The maximum biosorption of Fe(II) 43.43, Mn(II) 40.98 and Zn(II) 37.43 mg/g was achieved with Ca-alginate immobilized algal cells at optimum pH of 6.0, algal cells dosage 0.6 g/L, and contact time of 450 min at room temperature. The biosorption efficiency of freely suspended and immobilized C. vulgaris cells for heavy metals removal from the industrial wastewater was validated. Modeling of biosorption kinetics showed good agreements with pseudo-second-order. Langmuir and D-R isotherm models exhibited the best fit of experimental data. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) revealed that the biosorption of considered metal ions was feasible, spontaneous and exothermic at 25-45°C. The SEM showed porous morphology which greatly helps in the biosorption of heavy metals. The Fourier transform infrared spectrophotometer (FTIR) and X-rays Photon Spectroscopy (XPS) data spectra indicated that the functional groups predominately involved in the biosorption were C-N, -OH, COO-, -CH, C=C, C=S and -C-. These results shows that immobilized algal cells in alginate beads could potentially enhance the biosorption of considered metal ions than freely suspended cells. Furthermore, the biosorbent has significantly removed heavy metals from industrial wastewater at the optimized condition.

Performance Evaluation of a Thermophilic Anaerobic Membrane Bioreactor for Palm Oil Wastewater Treatment

Anaerobic treatment processes have achieved popularity in treating palm oil mill effluent due to its high treatability and biogas generation. The use of externally submerged membranes with anaerobic reactors promotes the retention of the biomass in the reactor. This study was conducted in thermophilic conditions with the Polytetrafluoroethylene hollow fiber (PTFE-HF) membrane which was operated at 55 °C. The reactor was operated at Organic Loading Rates (OLR) of 2, 3, 4, 6, 8, and 10 kg Chemical Oxygen Demand (COD)/m³·d to investigate the treatment performance and the membrane operation. The efficiency of the COD removal achieved by the system was between 93-98%. The highest methane yield achieved was 0.56 m³ CH₄/kg COD_r. The reactor mixed liquor volatile suspended solids (MLVSS) was maintained between 11.1 g/L to 20.9 g/L. A dead-end mode PTFE hollow fiber microfiltration was operated with the constant flux of 3 LMH (L/m²·h) in permeate recirculation mode to separate the clear final effluent and retain the biomass in the reactor. Membrane fouling was one of the limiting factors in the membrane bioreactor application. In this study, organic fouling was observed to be 93% of the total membrane fouling.

Dynamics of Microbial Populations Responsible for Biodegradation during the Full-Scale Treatment of Palm Oil Mill Effluent

Despite efforts to address the composition of the microbial community during the anaerobic treatment of palm oil mill effluent (POME), its composition in relation to biodegradation in the full-scale treatment system has not yet been extensively examined. Therefore, a thorough analysis of bacterial and archaeal communities was performed in the present study using MiSeq sequencing at the different stages of the POME treatment, which comprised anaerobic as well as facultative anaerobic and aerobic processes, including the mixed raw effluent (MRE), mixing pond, holding tank, and final discharge phases. Based on the results obtained, the following biodegradation processes were suggested to occur at the different treatment stages: (1) Lactobacillaceae (35.9%) dominated the first stage, which contributed to high lactic acid production; (2) the higher population of Clostridiaceae in the mixing pond (47.7%) and Prevotellaceae in the holding tank (49.7%) promoted acetic acid production; (3) the aceticlastic methanogen Methanosaetaceae (0.6–0.8%) played a role in acetic acid degradation in the open digester and closed reactor for methane generation; (4) Syntrophomonas (21.5–29.2%) appeared to be involved in the degradation of fatty acids and acetic acid by syntrophic cooperation with the hydrogenotrophic methanogen, Methanobacteriaceae (0.6–1.3%); and (5) the phenols and alcohols detected in the early phases, but not in the final discharge phase, indicated the successful degradation of lignocellulosic materials. The present results contribute to a better understanding of the biodegradation mechanisms involved in the different stages of the full-scale treatment of POME.

Physicochemical characteristics of microbial content in a modified anaerobic inclining-baffled reactor (MAI-BR) treating recycled paper mill effluent (RPME)

Microbial content formed in bioreactors plays a significant role in the anaerobic process. Therefore, the physicochemical characteristics of microbial content in a modified anaerobic inclining-baffled reactor (MAI-BR) treating recycled paper mill effluent (RPME) were investigated using Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG), and derivative thermogravimetric (DTG) analyses, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), Brunauer-Emmett-Teller (BET), and surface area analyzer. FTIR spectra revealed that the microbial content had stronger characteristic peaks corresponding to alcohols, water, lipids carbohydrates, proteins, and mineral compounds. Calcite, muscovite, and lepidolite were the prevalent mineral phases found by XRD analysis. The elemental of these minerals like C, Ca, N, O, and Si was confirmed by XPS results. The microbial content samples from each compartment showed similar thermal behavior. SEM images showed that straight rod-shaped and Methanosaeta-like microorganisms were predominant, whereas C, O, and Ca were noticed by EDS on the surface of granules. The BET surface areas and pores of granules are found to decline throughout the reactor's compartment, where Compartment 1 had the largest values. Thus, the findings of this study establish further understanding of the physicochemical properties of microbial content formed in MAI-BR during the RPME treatment.

Mass transfer kinetics of biosorption of nitrogenous matter from palm oil mill effluent by aerobic granules in sequencing batch reactor

Understanding of mass transfer kinetics is important for biosorption of nitrogen compounds from palm oil mill effluent (POME) to gain a mechanistic insight into future biological processes for the treatment of high organic loading wastewater. In this study, the rates of global and sequential mass transfer were determined using the modified mass transfer factor equations for the experiments to remove nitrogen by aerobic granular sludge accumulation in a sequencing batch reactor (SBR). The maximum efficiencies as high as 97% for the experiment run at [k_La]_g value of 1421.8 h^-1 and 96% for the experiment run at [k_La]_g value of 9.6 × 10³⁷ h^-1 were verified before and after the addition of Serratia marcescens SA30, respectively. The resistance of mass transfer could be dependent on external mass transfer that controls the transport of nitrogen molecule along the experimental period of 256 days. The increase in [k_La]_g value leading to increased performance of the SBR was verified to contribute to the future applications of the SBR because this phenomenon provides new insight into the dynamic response of biological processes to treat POME.

Bio-energy generation in an affordable, single-chamber microbial fuel cell integrated with adsorption hybrid system: effects of temperature and comparison study

A microbial fuel cell (MFC) integrated with adsorption system (MFC-AHS) is tested under various operating temperatures with palm oil mill effluent as the substrate. The optimum operating temperature for such system is found to be at ∼35°C with current, power density, internal resistance (R_in), Coulombic efficiency (CE) and maximum chemical oxygen demand (COD) removal of 2.51 ± 0.2 mA, 74 ± 6 mW m^-3, 25.4 Ω, 10.65 ± 0.5% and 93.57 ± 1.2%, respectively. Maximum current density increases linearly with temperature at a rate of 0.1772 mA m^-2 °C^-1, whereas maximum power density was in a polynomial function. The temperature coefficient (Q₁₀) is found to be 1.20 between 15°C and 35°C. Present studies have demonstrated better CE performance when compared to other MFC-AHSs. Generally, MFC-AHS has demonstrated higher COD removals when compared to standalone MFC regardless of operating temperatures.

ABBREVIATIONS

ACFF: activated carbon fiber felt; APHA: American Public Health Association; CE: Coulombic efficiency; COD: chemical oxygen demand; ECG: electrocardiogram; GAC: granular activated carbon; GFB: graphite fiber brush; MFC: microbial fuel cell; MFC-AHS: microbial fuel cell integrated with adsorption hybrid system; MFC-GG: microbial fuel cell integrated with graphite granules; POME: palm oil mill effluent; PTFE: polytetrafluoroethylene; SEM: scanning electron microscope.

Performance and kinetic evaluation of an integrated anaerobic-aerobic bioreactor in the treatment of palm oil mill effluent

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.

ABBREVIATIONS

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.