High Chemical Oxygen Demand Research Articles

Effect of electrode shape and deposition technique on electrochemical treatment of ampicillin in water

The effect of stainless steel (SS) electrode shape on electrochemical treatment of pharmaceutical pollutant has been studied. Anodes consisting of SS plate and SS grid coated with lead dioxide (PbO 2 ) were prepared by different deposition techniques: electrodeposition (ED), sol gel method (SG) using spin-coating (SC) and dip-coating (DC) depending on the electrode shape. The influence of the substrate shape and the deposition method on the oxidizing performance of the elaborated electrode was studied. The surface morphology and the composition of the PbO 2 layer were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). XRD analysis revealed the presence of β -PbO 2 form with both deposition techniques in addition to the chromium (Cr) phase attributed to the SS substrate. Electrochemical Impedance Spectroscopy (EIS) measurements were performed for assessing the electrochemical behavior of the SS/PbO 2 anodes. EIS results demonstrated a smaller charge transfer resistance with PbO 2 ED coating compared to PbO 2 SG . The degradation of ampicillin as pharmaceutical pollutant was evaluated with high performance liquid chromatography and chemical oxygen demand (COD) for overall mineralization of organic matter and to evaluate the related average current efficiency (ACE) and energy consumption (EC). This study demonstrated that SS grid /PbO 2 ED is the most efficient electrode for electrochemical treatment with 100% of ampicillin removal after 120 min of treatment. • Ampicillin degradation by anodic oxidation is studied. • Plate and grid substrates are used for the fabrication of PbO 2 anode. • PbO 2 coating is deposited by electrodeposition and sol gel techniques. • SS grid PbO 2 ED is the most efficient anode for ampicillin removal.

Insights into the technology utilized to cultivate microalgae in dairy effluents

The population increase has brought a number of consequences, such as greater demands for food, fossil fuels, and freshwater. The cultivation of microalgae appears to be an alternative source of food and energy because the biomass of microalgae can yield several products with applications in the fields of bioenergy, agriculture, and human and animal food. However, growing microalgae requires high concentrations of nutrients and water, making it an expensive process for large-scale production. The use of some effluents as culture media for microalgae has become a promising solution to reduce process costs and to obtain effluent treatment. The organic residues present in dairy effluent are considered harmful to the environment due to the high chemical and biochemical oxygen demand. Another problem is the high concentrations of nitrogen and phosphorus. However, these two nutrients are among the main nutrients used to grow microalgae. The ability of microalgae to effectively absorb nutrients from dairy effluent and the concomitant generation of value-added products make this effluent a potential medium for biomass production at a reduced cost. Therefore, this review aims to present recent advances in microalgae biotechnology for the treatment of dairy effluents. In addition, the review contributes to the existing literature by expanding knowledge about replacing drinking water and synthetic nutrients with dairy effluents in the cultivation of microalgae. This review shows the efficiency of the treatment of this effluent by microalgae and the possible applications of microalgae biomass cultivated in dairy effluents.

Quantification of land use/land cover impacts on stream water quality across Taiwan

Change in water quality is seen as a reflection of change in terrestrial and aquatic ecosystems that are degraded by anthropogenic activities, including inappropriate land use management, deforestation, and urbanization. As the inter-correlations among landscape structure and ecological process have great influences on the hydrological process, energy flow, and nutrient cycles, it is important to evaluate the impact of landscape configuration on water quality for individual basins. Spatio-temporal variations of water quality and correlations among land use/land cover and water quality across Taiwan have not been thoroughly investigated. In this study, 48 water quality stations within 10 basins across Taiwan are investigated to identify the relationships among various water quality indices, land use/land cover, and landscape metrics at two different time periods. A total of 12 water quality parameters are included: water temperature, pH value, electrical conductivity, dissolved oxygen, biological oxygen demand, chemical oxygen demand, total suspended sediment, total phosphorus, ammonia, nitrate, nitrite, and total nitrogen. Two years (1994 and 2007) of land use/land cover were characterized by using landscape metrics to quantify change in landscape configuration. The hypothesis is that individual basin has different characteristics resulting in different water quality – landscape metric relationships. The results showed that high degrees of landscape fragmentation and interspersion are correlated with degradation of water quality, in terms of high biological and chemical oxygen demands, and nitrogen loads, and such significant relationships are found in certain land use types as pollution sources. Only 3 out of 10 basins have strong or moderate impacts of landscape variation on water quality, indicating these findings could provide reference for developing an effective watershed planning and management with further investigations of landscape configuration at the class level.

Geographic distribution of net-zero energy wastewater treatment in China

In China, significant differences in climatic conditions, economic development levels, treatment processes used, and population density inevitably lead to regional patterns in the energy recovery and consumption of wastewater treatment plants (WWTPs). However, research is still lacking on characteristics of WWTPs in different regions and how potential patterns affect the energy self-sufficiency of WWTPs in China. In this study, the geographic distribution of the energy self-sufficiency of municipal wastewater treatment in China is investigated based on a net-zero energy (NZE) model. The results indicated that only 19% of the investigated WWTPs could generate enough energy to offset their energy consumption under their existing operating conditions. The maximum self-sufficiency rate was 186.43% among all of the investigated WWTPs in eastern China. Therefore, their current wastewater treatment operation strategies are not conducive to energy recovery. However, 30% of the investigated WWTPs could realize 100% energy self-sufficiency by adjusting their metabolic substrate allocation. There is a higher probability of achieving the NZE status in eastern and northeastern China due to more effective operations, higher chemical oxygen demand (COD) removals, and higher economic levels. A higher energy consumption and worse energy recovery performance lead to a low probability of achieving NZE in western China. However, in western China, there is a great potential for improving the energy self-sufficiency of the WWTPs by regulating their metabolic material allocations. These findings provide a nationwide perspective on energy-saving and emission reduction measures for WWTPs and facilitate the attainment of energy neutralization in the WWTPs in China.

Adsorption of organic matter from papermaking wastewater by CoFe2O4-coated sand in batch and fixed-bed systems

The secondary treated effluents of pulp and paper mills contain high chemical oxygen demand (COD) that is associated with organic matter. Therefore, this study explores the adsorption of substances contributing to COD using CoFe2O4 and quartz sand-coated CoFe2O4 in batch and fixed-bed column experiments. X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller analysis, and X-ray photoelectron spectroscopy were used to characterize the adsorbents. The quartz sand-loaded CoFe2O4 exhibited a larger pore volume and average pore size. Batch experiments revealed that adsorption on CoFe2O4 closely fit the pseudo-second-order model. To explore the effects of bed depth, feed flow rate, and initial solution pH on the breakthrough characteristics of CoFe2O4-coated sand, fixed-bed column experiments were conducted, and the breakthrough curves were drawn from the ratio of influent COD concentration to effluent COD concentration. The breakthrough time decreased with an increase in the feed flow rate and initial pH but increased with the bed depth. According to the X-ray photoelectron spectroscopy analysis, CoFe2O4-coated sand showed excellent stability due to negligible leaching of metallic elements. These findings have important implications for the advanced treatment of industrial wastewater.

Reconsidering hydrolysis kinetics for anaerobic digestion of waste activated sludge applying cascade reactors with ultra-short residence times

Hydrolysis is considered to be the rate-limiting step in anaerobic digestion of waste activated sludge (WAS). In this study, an innovative 4 stages cascade anaerobic digestion system was researched to (1) comprehensively clarify whether cascading configuration enhances WAS hydrolysis, and to (2) better understand the governing hydrolysis kinetics in this system. The cascade system consisted of three 2.2 L ultra-short solids retention times (SRT) continuous stirred tank reactors (CSTRs) and one 15.4 L CSTR. The cascade system was compared with a reference conventional CSTR digester (22 L) in terms of process performance, hydrolytic enzyme activities and microbial community dynamics under mesophilic conditions (35 °C). The results showed that the cascade system achieved a high and stable total chemical oxygen demand (tCOD) reduction efficiency of 40–42%, even at 12 days total SRT that corresponded to only 1.2 days SRT each in the first three reactors of the cascade. The reference-CSTR converted only 31% tCOD into biogas and suffered process deterioration at the applied low SRTs. Calculated specific hydrolysis rates in the first reactors of the cascade system were significantly higher compared to the reference-CSTR, especially at the lowest applied SRTs. The activities of several hydrolytic enzymes produced in the different stages revealed that protease, cellulase, amino peptidases, and most of the tested glycosyl-hydrolases had significantly higher activities in the first three small digesters of the cascade system, compared to the reference-CSTR. This increase in hydrolytic enzyme production by far exceeded the increase in specific hydrolysis rate, indicating that hydrolysis was limited by solids-surface availability for enzymatic attack. Correspondingly, high relative abundances of hydrolytic-fermentative bacteria and hydrogenotrophic methanogens as well as the presence of syntrophic bacteria were found in the first three digesters of the cascade system. However, in the fourth reactor, acetoclastic methanogens dominated, similarly as in the reference-CSTR. Overall, the results concluded that using multiple CSTRs that are operated at low SRTs in a cascade mode of operation significantly improved the enzymatic hydrolysis rate and extend in anaerobic WAS digestion. Moreover, the governing hydrolysis kinetics in the cascading reactors were far more complex than the generally assumed simplified first-order kinetics.

TREATMENT OF TRADITIONAL ETHANOL FERMENTATION WASTE WITH ELECTROLYSIS METHOD FOR DECREASING COD AND SULFIDE

Ethanol is produced from molasses by a fermentation process. In Bekonang, ethanol manufacturingby a home-scale industry so the waste just thrown away in free water then pollution occurs both in rivers and in paddy fields. Ethanol waste has very high chemical oxygen demand (COD) and contain high sulfide. Electrolysis that use for reduce leves COD dan Sulfide with electricity as main source for direct current flowing electricity (dc) to the anode and cathode. Electrolysis time 10, 15, 20, 25 and 30 minutes and voltage variation 5, 10 and 15 volt. Based on data obtained in the test COD obtained optimum levels of 284.5 mg/L from the initial content of 586 mg/L , at a time variation of 30 minutes and voltage 15 volt. The sulfide test obtained optimum levels of 0.0661 mg/L from the initial content of 0.305 mg/L, at time variation of 25 minutes and a voltage of 15 volt.

Central Composite Design: a Response Surface Methodology Approach in Biodegradation of Textile Dye Wastewater

Objectives : This study evaluated and identified the removal of colors and chemocal oxygen demands from thextile dye effluents by Bacillus cereus isolated from the local textile wastewater treatment plant.Methods : Central composite design (CCD) from response surface methodology (RSM) was applied in order to achieve the optimized treatment process condition for the textile dyes wastewater degradation. Two-level of three process parameters with six center points resulted a total of twenty runs of experiments were performed. Bacterial inoculum (-1,+1) (%, v/v), agitation (-1, +1) (rpm), and pH (-1, +1) were tested.Results and Discussion : During the ten days of biodegradation process, highest decolourization achieved was 88.67% with low pH and agitation; and medium level of initial concentration of bacterial inoculum. Highest chemical oxygen demand (COD) removal was achieved with 99.20% from high pH (pH 10), low agitation (100 rpm) and high initial concentration of bacterial inoculum (15%, v/v).Conclusions : The biological treatments was able to remove colour and chemical oxygen demand with application of CCD, giving the optimum settings of the three process parameters studied.

Nitrogen removal and bacterial mechanism in a hybrid anoxic/oxic baffled reactor affected by shortening HRT in treating manure-free piggery wastewater

A hybrid anoxic/oxic baffled reactor (HAOBR) with four compartments was constructed to treat manure-free piggery wastewater which was characterized by high ammonium (NH4+-N) and low chemical oxygen demand (COD) to total nitrogen (TN) ratio. To evaluate the suitable volumetric removal rate, hydraulic retention time (HRT) was decreased from 28 h to 16 h by stages, with the constant reflux ratio of 200% at 32 ± 1 °C. It was found that the optimal HRT is 20 h with the removal efficiency of COD, NH4+-N and TN in the steady phase averaging 79.1%, 99.5% and 93.2%, respectively. Meanwhile, the COD removed to TN removed ratio (CODrem/TNrem) averaged 0.94, indicating that anammox was the main approach to TN removal. Microbial community analysis further revealed that the main nitrogen removal pathway in the first two anaerobic compartments was heterotrophic denitrification, while autotrophic partial nitritation - anammox process dominated the last two aerobic compartments. This study presented a cost-effective bioprocess for treating organic wastewater with high NH4+-N and low COD/TN ratio.

A critical review of state-of-the-art electrocoagulation technique applied to COD-rich industrial wastewaters.

Electrocoagulation (EC) is one of the emerging technologies in groundwater and wastewater treatment as it combines the benefits of coagulation, sedimentation, flotation, and electrochemical oxidation processes. Extensive research efforts implementing EC technology have been executed over the last decade to treat chemical oxygen demand (COD)-rich industrial wastewaters with the aim to protect freshwater streams (e.g., rivers, lakes) from pollution. A comprehensive review of the available recent literature utilizing EC to treat wastewater with high COD levels is presented. In addition, recommendations are provided for future studies to improve the EC technology and broaden its range of application. This review paper introduces some technologies which are often adopted for industrial wastewater treatment. Then, theEC process is compared with those techniques as a treatment for COD-rich wastewater. The EC process is considered as the most privileged technology by different research groups owing to its ability to deal with abundant volumes of wastewater. After, the application of EC as a single and combined treatment forCOD-rich wastewaters is thoroughly reviewed. Finally, this review attempts to highlight the potentials and limitations of EC. Related to the EC process in batch operation mode, the best operational conditions are found at 10 V and 60 min of voltage and reaction time, respectively. These last values guarantee high COD removal efficiencies of >90%. This review also concludes that considerably large operation costs of the EC process appears to be the serious drawback and renders it as an unfeasible approach for handling of COD rich wastewaters. In the end, this review has attempted to highlights thepotential and limitation of EC and suggests that vast notably research in the field of continuous flow EC system is essential to introduce this technology as a convincing wastewater technology.

Utilization of Activated Corn Cob (Zea Mays) as an Improved Adsorbent for Reducing Chemical Oxygen Demand (COD) Value from Waste of the Sasirangan Industry

Liquid waste from sasirangan industrial activities has a high enough Chemical Oxygen Demand pollutant power; if it is directly discharged into water bodies, it can damage the environment and harm health. One of the first processes needs to be done by using activated corn cobs (Zea mays). This study aims to analyze the ability of corn cobs charcoal to reduce levels of Chemical Oxygen Demand and increase the pH of sasirangan waste so that the results of this study can be an alternative to natural-based sasirangan waste treatment. This type of research is a pure experiment with a research design in One Group Pretest Postest Design. The research material used was sasirangan industrial waste in Manarap Village, Kertak Hanyar District, Banjar Regency, South Kalimantan, Indonesia. Chemical Oxygen Demand levels were determined by the closed reflux titrimetry method. The results showed that the addition of the highest dose of activated corncob charcoal (50 g) reduced the largest turbidity by 35 percent, increased the pH by 72 percent, and reduced the color intensity by 33 percent. The conclusion is that the addition of corncob-activated charcoal at a dose of 30gr, 40gr, 50gr can reduce levels of Chemical Oxygen Demand, respectively, namely 24 percent, 35 percent, and 33 percent. An increase in pH was found at the same dose of 46 percent, 62 percent, and 72 percent, respectively. There is an effect of increasing the mass of activated charcoal from corn cobs on the Chemical Oxygen Demand levels in the sasirangan industrial waste with a significance value of 0.007. It is suggested to use corn cobs-activated charcoal for the pretreatment stage of sasirangan industrial waste treatment.

Performance of Food Waste Feeding Pilot Plant Biodigester Operated with Identified Potential Substrate Properties

Anaerobic digestion has been proven as sustainable process technology for organic waste conversion into renewable bio-energy. This study was conducted to evaluate the performance of mono-digestion process for different types of food waste substrates using pilot scale anaerobic bio-digester (1200 L) in terms of biogas production and the chemical oxygen demand (COD) removal efficiency. The biochemical methane potential (BMP) test of rice waste (R), vegetable waste (VW) and coconut meat residue (CMR) were tested at initial volatile solid (VS) loading of 0.1631, 1.1690, 1.0059 g VS/L, respectively at fixed inoculum/substrate (I/S) ratio of 0.5. Further study conducted by using rice waste (R) in pilot plant anaerobic bio-digester (1200L) for 43 days to investigate the reactor performance in term of COD removal efficiency. Interestingly, inoculum used for this study performs very well and able to digest food waste. Results demonstrate that the maximum specific biogas yield (SBY) was observed from rice waste (R) at 0.0587 L/kg VS compared to other substrates. Specific biogas yield (SBY) of rice waste (R) was 16.01% and 11.92% higher than substrate vegetable waste (VW) and coconut meat residue (CMR) respectively. High COD removal efficiency of pilot plant bio-digester (up to 93 %) using rice waste (R) as sole substrate indicates a good performance of reactor in treating food waste. Conversion of food waste to biogas in pilot plant bio-digester is highly potential as one of the sustainable waste treatment technology.

Integrated process for protein, pigments, and biogas production from baker's yeast wastewater using filamentous fungi

Baker's yeast production industry generates large quantities of high chemical oxygen demand (COD) wastewater. The integration of baker's yeast wastewater (BYW) for an innovative two-step waste biorefinery process by producing protein-rich fungal biomass and biogas along with COD and nutrients removal was the main object of the present research. In the first step, fungal biomass production from BYW was investigated using four species of filamentous fungi. The maximum biomass yield of 5.13 g/L BYW containing 43.8% mycoprotein and 36.3% COD removal was achieved by A. oryzae. In the second step, to produce biogas and further remove organic matter, the effluent of fungal fermentation was subjected to anaerobic digestion and COD removal between 22.4 and 44.2% was obtained. Overall, 1 m3 of BYW yielded 5.13 kg of protein-rich biomass and 1.42 m3 of methane. Additionally, pigment production using N. intermedia was investigated, and 1.54 mg carotenoids/g biomass was produced.

SARS-CoV-2: fate in water environments and sewage surveillance as an early warning system.

The carwash is known as one of the most important urban services that brings about the production of huge volume of wastewater with high turbidity and high chemical oxygen demand (COD). Seasonal and carwash location features affect the quality of carwash wastewater. Various methods with special focus on chemical processes have been employed for carwash wastewater treatment and eliminating different pollutants from this wastewater of great concern for the environment. This review was conducted for identifying and comparing the efficiency of chemical processes for carwash wastewater treatment. To this aim, key words were identified and a search protocol was defined to search studies in three databases: Scopus, Web of Science, and PubMed. The results of this systematic review indicated that coagulation (66%) is the most common chemical processes for carwash wastewater treatment. Although chemical processes are able to reduce the turbidity and COD over 80%. Due to the characteristics of carwash wastewater, chemical processes are a necessary pretreatment for processes such as membrane technology. Rapid treatment and high efficiency are the advantages of wastewater treatment by chemical methods, but the energy consumption and sludge volume are two main factors in selection the chemical processes for carwash wastewater treatment.

Geochemical characterization and the assessment of trace element retention in sediments of the Reconquista River, Argentina.

The mineralogical and geochemical characterization of sediments of the Reconquista River allows analyzing the geochemical partition of trace elements in one of the most polluted water courses of Argentina. The low dissolved oxygen and high ammonia contents, together with the high chemical oxygen demand, attest to the poor water quality. Ammonia, Cd and Cu content in surficial water exceeds the maximum guidelines for freshwater in Argentina. The recent sediments of the uppermost bed are enriched in organic matter (OM), sulfur, Zn, Cu and Pb. The enrichment factor is moderate, and the geoaccumulation index (Igeo) for Cu and Pb indicates uncontaminated to moderately contaminated sediments. The positive and significant correlation between As, Cr, Pb and Zn with the iron content suggests that their retention is controlled by the amount of iron oxy (hydr)oxides in the sediments, probably combined with the silt + clay abundance. In comparison with its tributary, the Las Catonas Stream, the Reconquista River, has less OM and trace elements in the sediments and more dissolved trace elements in the interstitial water. We interpret that OM is the main sorbent of the trace element. In the absence of OM, the iron oxy (hydr)oxides and the silt + clay fraction are a less efficient substitute. Consequently, the interstitial waters of the Reconquista River are enriched in these elements. Therefore, minor changes in the environmental conditions may generate significant release of hazardous trace elements from the sediments to the interstitial water and, in turn, to the surficial water of the river. As most of the big cities and the agricultural activities of Argentina are developed on the loessic substrate, the understanding of its interaction with polluted waters is crucial.

Treatment of Cutting Oil-in-Water Emulsion by Combining Flocculation and Fenton Oxidation

Recently, the disposal of waste oil-in-water cutting emulsion has become an urgent issue because of its extremely high chemical oxygen demand (COD). The present work focuses on treating the waste cutting emulsion generated from the Samsung Thai-Nguyen factory in Vietnam. This work used multistage methods to treat the waste cutting emulsion to meet the wastewater disposal requirement and characterize the oil recovered. The multistage methods consist of the flocculation method (stage 1) and Fenton oxidation (stage 2). The wastewater after stage 1 treatment has a COD reduction efficiency of 98.24% at the condition of pH 5, Al2(SO4)3 2 g/L, C-PAM 12 mg/L, stirring speed 50 rpm, and stirring time 15 minutes. At that condition, the COD value decreased from 147200 mg/L to 2484 mg/L. After stage 2, the COD value further decreased from 2484 mg/L to 85.4 mg/L with total COD removal efficiency increasing to 99.9% at the optimum conditions of pH 3, H2O2 : FeSO4 concentration ratio of 10 : 1, and FeSO4 concentration of 14.04 g/L. After the stage 2 treatment, the wastewater with the COD value of 85.4 mg/L and BOD5 value of 30 mg/L satisfied the Vietnam standard grade B and grade A, respectively, for industrial wastewater. The oil recovered from the treatment has a heating value of 38095 ± 8 kJ/kg, and thus, it could be reusable as fuel gas.

Characterization of the Fermentation and Sensory Profiles of Novel Yeast-Fermented Acid Whey Beverages.

Acid whey is a by-product generated in large quantities during dairy processing, and is characterized by its low pH and high chemical oxygen demand. Due to a lack of reliable disposal pathways, acid whey currently presents a major sustainability challenge to the dairy industry. The study presented in this paper proposes a solution to this issue by transforming yogurt acid whey (YAW) into potentially palatable and marketable beverages through yeast fermentation. In this study, five prototypes were developed and fermented by Kluyveromyces marxianus, Brettanomyces bruxellensis, Brettanomyces claussenii, Saccharomyces cerevisiae (strain: Hornindal kveik), and IOC Be Fruits (IOCBF) S. cerevisiae, respectively. Their fermentation profiles were characterized by changes in density, pH, cell count, and concentrations of ethanol and organic acids. The prototypes were also evaluated on 26 sensory attributes, which were generated through a training session with 14 participants. While S. cerevisiae (IOCBF) underwent the fastest fermentation (8 days) and B. claussenii the slowest (21 days), K. marxianus and S. cerevisiae (Hornindal kveik) showed similar fermentation rates, finishing on day 20. The change in pH of the fermentate was similar for all five strains (from around 4.45 to between 4.25 and 4.31). Cell counts remained stable throughout the fermentation for all five strains (at around 6 log colony-forming units (CFU)/mL) except in the case of S. cerevisiae (Hornindal kveik), which ultimately decreased by 1.63 log CFU/mL. B. bruxellensis was the only strain unable to utilize all of the sugars in the substrate, with residual galactose remaining after fermentation. While both S. cerevisiae (IOCBF)- and B. claussenii-fermented samples were characterized by a fruity apple aroma, the former also had an aroma characteristic of lactic acid, dairy products, bakeries and yeast. A chemical odor characteristic of petroleum, gasoline or solvents, was perceived in samples fermented by B. bruxellensis and K. marxianus. An aroma of poorly aged or rancid cheese or milk also resulted from B. bruxellensis fermentation. In terms of appearance and mouthfeel, the S. cerevisiae (IOCBF)-fermented sample was rated the cloudiest, with the heaviest body. This study provides a toolkit for product development in a potential dairy-based category of fermented alcoholic beverages, which can increase revenue for the dairy industry by upcycling the common waste product YAW.

Waste management of the palm oil industry: present status and future perspective

Numerous research and developments have emerged in the last 100 years, primarily dedicated to waste management. Among the subjects they have focused on are life-cycle assessments, treatment and minimisation of waste and mitigation of waste environmental impact. These massive efforts came into effect to mitigate the detrimental impacts of waste generation from production industries. One industry that has been plagued with rising sustainability issues is the palm oil industry, which is the main engine of development in South East Asia. The oil palm is a significant flex crop. In Malaysia and Indonesia particularly, crude palm oil production has raised red flags due to its massive waste generation. To illustrate, different types of wastes are generated from 1 t of processed fresh fruit bunches – namely, palm oil mill effluent (POME) (60%), empty fruit bunches (23%), mesocarp fibres (12%), shell (5%) and gas emissions. The high nitrogen content, high chemical oxygen demand and biochemical oxygen demand of POME cause severe environmental pollution. Nevertheless, the biomethane generated from POME through anaerobic digestion can be harnessed as renewable bioenergy. Hence, the sustainability of the palm oil industry could be ensured by combining both the production of renewable energy and the treatment of waste water.

Effects of Enzyme Volumes on Hydrolysis and Fermentation for Ethanol Production From Leftover Cooked Rice.

This study aimed to utilize the enzymatic hydrolysis of leftover cooked rice (LCR) for fermentative ethanol production. Effect of glucoamylase volumes (V1: 5 U/g, V2: 25 U/g, and V3: 50 U/g) on the performance of LCR hydrolysis was also evaluated. It was found that the highest chemical oxygen demand (COD) of 77.5 g/L and reducing sugar (RS) of 34.6 g/L were achieved at V3. The LCR hydrolyzate obtained from enzymatic hydrolysis was then used as feedstock for ethanol fermentation. Higher ethanol production was obtained when RS increased from 18.7 g/L (V1) to 23.2 g/L (V2). However, lower ethanol production was found when RS further increased to 34.6 g/L (V3) probably because too high RS concentration led to the inhibition on the yeast. The maximum ethanol production and yield were 21.1 g/L and 0.3 g ethanol/g LCR, respectively. The LCR could be a promising substrate for fermentative ethanol production for industrial application.

Enhanced HCB removal using bacteria from mangrove as post-treatment after electrochemical oxidation using a laser-prepared Ti/RuO2–IrO2–TiO2 anode

The environmental persistence of hexachlorobenzene (HCB) is a challenge that promotes studies for efficient treatment alternatives to minimize its environmental impact. Here, we evaluated the HCB removal by electrochemical, biological, and combined approaches. The electrochemical treatment of 4 μM HCB solutions was performed using a synthesized Ti/RuO2–IrO2–TiO2 anode, while the biological treatment using mangrove-isolated bacteria was at 24, 48, and 72 h. The HCB degradability was assessed by analyzing chemical oxygen demand (COD), microbial growth capacity in media supplemented with HCB as the only carbon source, gas chromatography, and ecotoxicity assay after treatments. The synthesized anode showed a high voltammetric charge and catalytic activity, favoring the HCB biodegradability. All bacterial isolates exhibited the ability to metabolize HCB, especially Bacillus sp. and Micrococcus luteus. The HCB degradation efficiency of the combined electrochemical-biological treatment was evidenced by a high COD removal percentage, the non-HCB detection by gas chromatography, and a decrease in ecotoxicity tested with lettuce seeds. The combination of electrochemical pretreatment with microorganism degradation was efficient to remove HCB, thereby opening up prospects for in situ studies of areas contaminated by this recalcitrant compound.