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FeCoNiAlSi and FeCoNiAlBSi high entropy alloys (HEAs) were synthesized by mechanical alloying. Phase evolution, crystallite size, lattice strain, microstructure and morphology for the two alloys were investigated. It was found that two simple structures which are face-centred cubic (FCC) and body-centered cubic (BCC/B2) solid solution appear in FeCoNiAlSi HEA after 50 h of milling. Formation of Fe2B peak was observed in the XRD pattern when a small amount of boron was added to the base alloys. The particle size of the alloy was increased after 20 h of milling time. The structural analysis shows that the average crystallite size decreases while lattice grain size increases with the increasing milling time. The morphology structure of the milled powders shows the particles size becomes rounded, flat and rough as the milling time prolongs. The newly developed HEA synthesized by mechanical alloying is expected to provide prominent efficiency in degradation of azo dyes (Methyl Orange). Although the HEAs have been reported to provide larger surface area and excellent capacity, only a few studies have been reported on degradation of azo dye by using HEAs as catalyst. Therefore, the method derived from the results of this study will contribute in treating azo dyes for wastewater treatment. Keywords: azo dye; high entropy alloys; mechanical alloying; crystal structure; morphology

The performance of factorial designs is still limited due to some uncertainties that usually intensify process complexities, hence, the need for inter-platform auto-correlation analyses. In this study, the auto-correlation capabilities of factorial designs and General Algebraic Modeling System (GAMS) on the effects of some pertinent operating variables in wastewater treatment were compared. Individual and combined models were implemented in GAMS and solved with the trio of BARON, CPLEX and IPOPT solvers. It is revealed that adsorbent dosage had the highest effect on the process. It contributed the most effect toward obtaining the minimum silica and TDS contents of 13 mg/L and 814 mg/L, and 13.6 mg/L and 815 mg/L from factorial design and GAMS platforms, respectively. This indicates a concurrence between the results from the two platforms with percentage errors of 4.4% and 0.2% for silica and TDS, respectively. The effects of the mixing speed and contact time are negligible.

This study briefly reviews the recent advances in membrane and separation technology for antifouling strategies for membrane ultrafiltration. Membrane fouling is inevitable in ultrafiltration due to the eventual membrane pore blockage with foulants. Consequently, flux declines and affects the membrane integrity over time along with elevation in processing time and thereby complicating the overall membrane maintenance. To combat this issue, several studies had been undertaken such as grafting of TiO2 nanotubes (TNTs), graphene oxide nanosheets, zwitterions or polymers in the membrane and also by applying direct current. Moreover, many researchers emphasized on the integration of an enhanced pre-treatment process such as adsorption, coagulation, electrocoagulation and so on. By critically analysing and comparing the existing studies, the impact, suitability, efficiency and sustainability of the antifouling strategies will be discussed in this review. This refined approach of observing the progress in membrane technology will enable the determination of the existing gaps in the studies and will help to expand and propel the field further in separation efficiency.

The production of biogas from food waste is a good approach to the minimization of food waste and increase in the production of renewable energy. However, the use of food waste as a feedstock for biogas production currently poses a difficulty due to an ineffective hydrolysis process, which is a pretreatment procedure and the initial step of the biogas conversion process. This restriction results from the food waste polymers’ solubilization and breakdown. This has an impact on the volume of biogas produced during the methanogenesis stage. It is essential to increase the biodegradation of organic compounds (OC) during the hydrolysis process to increase biogas generation. This study focuses on the enhancement of biogas production by the anaerobic digestion (AD) of food waste (FW). FW was hydrolyzed by the immobilized biofilm and digested anaerobically in a semi-continuous digester. Four different digesters including the control were prepared. The control digester composed of no hydrolyzed food waste had no immobilized biofilm while the other three digesters had immobilized biofilm-hydrolyzed food waste with inoculum concentrations of 10%, 30%, and 50%. The results showed that the 50% digester had the highest biogas yield of about 2000 mL/500 mL. The 10%, 30%, and control digesters had a biogas yield of 1523 mL, 753 mL, and 502 mL respectively. Thus, the analysis of total volatile solid (TVS) reduction in the digesters with 10%, 30%, and 50% inoculum and the control have increased to 43.4% for the digesters with 30% and 10%, 60% for the digester with 50% inoculum, and only 29% for the control. Total chemical demand (TCOD) removal increased to 29%, 33%, 43%, and 56% for the control, and 10%, 30%, and 50%, respectively for the inoculum-to-feed ratio. From these results, the 50% inoculum-to-feed ratio has shown the highest biogas production and highest degradation based on TVS reduction and TCOD reduction. Based on this study, the biofilm pretreatment method can be considered a promising method for the enhancement of biogas volume and biodegradation. Biogas production was high (2000 mL) for hydraulic retention time (HRT = 20) days but the HRT = 15 days was also able to produce a significant amount (1400 mL) of biogas and the 50% inoculum-to-feed ratio has shown the highest volume of biogas production.

The present study shows the opportunity of using biofilm in the hydrolysis step of food waste (FW) to increase biogas production. Therefore, screened biofilm-producing microorganisms were adopted to facilitate the biodegradation of organic compounds (OCs) and enhance the volume of biogas production. The biofilm-producing microorganisms were first immobilized on a granular activated carbon (GAC) surface, and the optimum values of immobilization time, mass of the GAC surface, and size of the microbial inoculums were found using the statistical methods of one-factor-at-a-time (OFAT) and the response surface methodology (RSM) using a face-centered central composite design (FCCCD). Based on the results, 48 h of incubation, 8 g of GAC, and 1 mL of inoculum were the optimum conditions when shaken at 37 °C and 150 rpm. Different biofilm amounts (328 mg, 492 mg, 656 mg, 820 mg, and 984 mg) were used in hydrolysis flasks operated in batch mode to increase the degradation of the OCs. The optimal level of the hydrolysis degradation was on day 3 and at 328 mg of biofilm; the total solid (TS) content was decreased from 115 gL−1 to 79 gL−1 (31%), and the TCOD was decreased from 85.33 gL−1 to 54.50 gL−1 (36%).

This study focuses on rainwater harvesting quality at the Faculty of Engineering, International Islamic University Malaysia (IIUM). As development is progressing over the years in Malaysia, there is also an increasing number of environmental issues and those issues are getting worse day by day. At present, Malaysia is blessed with plentiful annual rainfall that represents approximately 314 mm of monthly rainfall but there is no evidence that this rainwater is redirected for daily usage. To pursue a more sustainable development, rainwater harvesting has been recognized as one innovative solution. The IIUM Gombak campus is located in a hillside area that is a suitable study area to perform rainwater harvesting, which can be used as an alternative water supply in the future and reduce utility bills for water used on the campus. Firstly, a suitable study area for rain water harvesting around KOE, IIUM was determined before collection of data to determine the storage capacity needed. This study includes the estimation of rainwater quantity that can be harvested in one year. The quality of rainwater in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), pH, total suspended solid (TSS), turbidity, and microbial count were studied. Data analysis showed that the values of BOD, COD, pH, TSS, turbidity, and microbial count were in the range of 2 - 3.2 mg/l, 22.5 – 42.5 mg/l, 5.9 - 6.5, 20 mg/l, 9 -11 NTU, and between 200 -260 cfu/ml, respectively. This indicates that the harvested rainwater is acceptably clean but not suitable to be used as drinking water. ABSTRAK: Fokus kajian ini adalah pada kualiti air hujan yang ditadah di Fakulti Kejuruteraan, Universiti Islam Antarabangsa Malaysia (UIAM). Sejajar dengan pembangunan pesat di Malaysia, isu alam sekitar juga semakin bertambah dan menjadi semakin teruk hari ke hari. Pada masa sama, ketika ini Malaysia dirahmati dengan hujan yang mencurah setiap tahun, dengan kuantiti bulanan sebanyak 314 mm air hujan dan tidak ada bukti penggunaan air hujan ini bagi kegunaan harian dsb. Bagi memenuhi keperluan kelangsungan pembangunan, penadahan air hujan dikenal pasti sebagai satu penyelesaian inovatif. Kampus UIAM Gombak terletak di kawasan pinggiran bukit yang sesuai bagi menjalankan kajian tadahan air hujan. Ianya boleh digunakan sebagai bekalan air alternatif pada masa depan dan mengurangkan bil utiliti bekalan air dalam kampus. Terlebih dahulu, kawasan kajian yang sesuai dikenal pasti berdekatan Fakulti Kejuruteraan, UIAM bagi mengumpul air hujan sebelum data dikumpulkan bagi mengenal pasti kapasiti pengumpulan yang diperlukan. Kajian ini juga menganggar kuantiti air hujan yang boleh ditadah dalam satu tahun. Kualiti air hujan dikaji dari segi keperluan oksigen biokimia (BOD), keperluan oksigen kimia (COD), pH, jumlah pepejal terampai (TSS), kekeruhan dan bilangan mikrob. Analisis data mendapati nilai BOD, COD, pH, TSS, kekeruhan dan bilangan mikrob berada dalam julat 2 - 3.2 mg/l, 22.5 – 42.5 mg/l, 5.9 - 6.5, 20 mg/l, 9 -11 NTU dan antara 200 -260 cfu/ml, masing-masing. Ini menunjukkan air hujan yang ditadah adalah boleh diterima sebagai bersih tetapi tidak sesuai dijadikan sebagai air minuman

The integrated bacterial mixed culture consortium with disproportionate oxygen demand was discovered to mutually cooperate with one single biofilm in oxidizing sulfide at different concentration. The present work was carried out to verify the potential of bacterial mixed culture (BMC) in developing a predictive optimum condition for sulfide oxidation in a laboratory batch mode. A face centered central composite design (FCCCD) under response surface methodology (RSM) was employed to predict the synergistic effects of initial hydrogen sulfide concentration (100–500 ppm), temperature (30–40 °C) and aeration rates (50–250 vvm) on BMC sulfide oxidation. A total number of 20 experimental runs with 6 centre points were carried out. The obtained results were analyzed using design expert and statistical validation indices to check the adequacy of the obtained quadratic models. The analysis of variance showed that more than 99% of the variation was explained by the models. There was a good agreement between experimental and predicted data. The optimum sulfide removal of 448.75 ppm was achieved at the temperature of 32.4 °C, initial hydrogen sulfide of 500 ppm and aeration rates of 110.06 vvm in 8 h. Therefore, the finding depicts the adequacy of the obtained model in enhancing BMC sulfide oxidation conditions. The model is further affirmed through SEM-EDXS analysis, revealing oxidized sulfide product aggregate of the micrographs coupled with elemental identification and quantitative composition.

Moringa oleifera is a well-known tropical plant with myriads medicinal and nutritional benefits. Its nutraceutical functions are due to the presence of mineral element and phytochemical components which necessitate their profiling. In this study, the elemental and chemical profiles of husk wastes from Moringa oleifera plants were elucidated using Liquid Chromatography equipped with an electrospray time-of-flight mass spectrometer (LCMS-QToF) and X-ray Fluorescence analyser. The confirmation of 493 bioactive compounds and two higher concentrations of micronutrients (calcium and potassium) indicated the potential of the Moringa oleifera extracts for medicinal and nutritional purposes. Also, the minimal presence of trace elements such as Cu, Si, Mo and Sr showed that they are non-toxic and can therefore be used as food supplement for both human and in animal feed. The result of this researchcould therefore provide lead for future investigation.

Expression of non-Newtonian fluid/solid mixture is often encountered in the fields of polymer and food industries. However, a reliable method for the design of the expression process has not been established. In this study, we conducted expression experiments of power law non-Newtonian fluid/solid mixture under constant pressure condition. The basic consolidation equation was derived by combining the fundamental equation for power law non-Newtonian flow through the cake with the equation of continuity and solved numerically using the Runge–Kutta method. The progress of the expression is represented by an average consolidation ratio Uc. The agreement between calculated and experimental Uc was satisfactory when the creep deformation of the material was taken into consideration. It was also elucidated that the consolidation time required for attaining a certain degree of primary consolidation depends on the (N + 1)/N-th power of the total volume of the solid material ω0, where N is the flow behavior index of the squeezed liquid. On the other hand, the creep constants B, the ratio of creep deformation to the total deformation, and η, a measure of the rate of creep deformation, both were found to be ω0-independent parameters, supporting the validity of the assumption made in the theoretical derivation.

The modeling of Pseudomonas putida growth is facilitated due to its nonfastidious nature. This research was performed to develop a predictive model for the growth of P. putida in a shake flasks medium. Methods: A response surface methodology (RSM) was employed to predict the synergistic effects with a combination of nutrient concentration (4-16 g/l), agitation (140-200 rpm) and temperature (30-40 oC) on P. putida (ATCC 49128) growth and cell biomass accumulation. The growth curves generated under different conditions were fitted using a nonlinear regression model equation. The relationship between the response and growth limiting variables were modelled using a face-centered central composite design (FCCCD) quadratic polynomial equation. Results: The predictive model was highly significant (p < 0.01), and the predicted values of the growth parameters obtained using the model equations were in agreement with the observed values (R2= 0.9840). The established model validation indices for describing the growth rate of P. putida were within the acceptable limit of bias (Bf) and accuracy factor (Af). Conclusion: Therefore, the predictive model further confirmed the versatility of P. putida to simple growth media within defined optimal physical operational parameters of simple batch mode.

application/pdf, Article, Separation Science and Technology. 2018, 52 (18), p.2804-2816

The present study aimed at the screening of parameters for electrocoagulation treatment of treated palm oil mill effluent using minimum-runs resolution IV design. The responses examined include: chemical oxygen demand removal (%), total suspended solids removal (%) and turbidity reduction (%), and the varied dependent factors comprise: electrical current density (mA/cm2), time (min), pH, electrolyte concentration (g/L), stirring speed (rpm), electrode spacing (mm) and electrode configuration (monopolar or dipolar). The statistical results revealed that the current density has a significant influence on the treatment performance at two-level interactions with pH, electrode spacing and electrode concentration and at three-level correlations with time and pH. Thus, the most important factors affecting the removal efficiency of the organic compounds were found to be pH, time, electrode spacing, electrolyte concentration and electrode configuration at a P value less than 0.05, respectively, in the descending order of significance. Therefore, the optimized electrocoagulation process could be reached with current density equal to 5 mA/cm2, electrolysis time of 5 min, electrode spacing of 5 mm and using monopolar electrode configuration. This combination provided the maximum ability of the process for chemical oxygen demand (68.84%), total suspended solids (93.27%) and turbidity reduction (92.88%) predictions, with the corresponding experimental values of 69.27, 97.59 and 96.91%, respectively.

Durian peel is among the renewable biomass wastes abundantly available in Malaysia. An implication of untreated biological materials for biosorption process was intensively reported, that prioritize our work towards sorbent modification. The biosorption potentials of hydrochloric acid (HCl) modified durian peels (HAMDP) for removal of Zn (II) from simulated wastewater was investigated. Characterization of HAMDP was performed by ATR-FTIR, SEM and BET. Spectroscopic studies showed the predominant contributors for Zn (II) biosorption on HAMDP is attributed to hydroxyl, carbonyl, carboxyl and amides groups. Batch adsorption studies revealed optimum conditions of pH 8, 0.5 g biosorbent dose, 4 h contact time and reaction temperature of 313 K. Non-linear isotherm models suggested applicability of Tempkin and Langmuir models at 313 K. The Langmuir maximum adsorption capacity was 36.73 mg/g. Kinetic studies revealed applicability of pseudo-second-order model. Webber-Morris model indicated possible role of diffusion of Zn (II) within the particles of HAMDP during the sorption process. Freundlich constant and activation energy values confirmed the physical nature of the process. Thermodynamic studies indicated that the process is exothermic and spontaneous. Regeneration studies depicted that HAMDP is economically viable. Conclusively, HCl served two significant purposes, namely; a good modification reagent and best eluent in Zn (II) recovery. Therefore, HAMDP is relatively effective, efficient, economical and most importantly “renewable and sustainable” biosorbent for Zn (II) removal from wastewater.

Electrocoagulation (EC) is a sustainable wastewater treatment alternative that is widely studied because of its environmentally friendly nature, versatility, and simplicity in setup and operation. However, EC alone cannot treat wastewater up to reusable standards and requires integration with other processes, mostly by adding highly hazardous oxidants. This work aims to investigate the combination of powdered activated carbon (AC) with biotreated palm oil mill effluent (BPOME) as wastewater sample, in the EC reactor, and to optimize its concentration for maximum pollutant removal efficiency. Ranging from 0.5-1.5 wt. % concentration of AC mixed with EC reactor, EC was carried out with its critical parameters set to a current of 1.75 A (i.e., 160 mA/cm2 current density) and initial pH 6 and 10 mm interelectrode distance with aluminum electrodes. The EC treated wastewater was sampled from 5 minutes to 60 minutes and the parameters monitored were total suspended solids (TSS), turbidity, color and chemical oxygen demand (COD). Turbidity, TSS and color were removed nearly to completion within 5 to 15 minutes of EC, whereas maximum COD removal was determined to be 84.6 % with 1 wt. % powdered AC combined with EC, which is an increase of about 14.6% compared to EC with no AC addition. The optimum concentration of AC for maximum removal efficiency on BPOME was 1 wt. % (2 g per 200 ml). Addition of AC in EC resulted in a faster pollutant removal rate, with enhanced process efficiency.

application/pdf, Article, Journal of Chemical Engineering of Japan. 2018, 51 (1), p.71-78

The clarification method by using composite dry powdered flocculants consisting of inorganic flocculant, polymer flocculant and flocculation aid has been proposed in the literature. Such composite flocculants are conveniently used in the flocculation process of small volume suspensions; i.e. the composite dry powdered flocculants are added directly to a suspension. However, very limited work has been reported on the flocculation behavior when composite flocculants are used in powder form. In this study, the effect of both dosages of dry powdered inorganic flocculant and ionic polymer flocculant on turbidity removal of PMMA suspension is investigated. Floc characteristics, such as sludge volume and floc strength, are also discussed. It is found that there exist various combinations of inorganic and polymer flocculant dosages resulting in sufficient turbidity removal; as the dosage of inorganic flocculant is increased, the suitable dosage of ionic polymer flocculant is also increased for better turbidity removal. Among these combinations of inorganic and polymer flocculant dosages, floc strength in higher dosages is larger than that in lower dosages. It is also found that in the higher polymer dosage conditions, flocculated sludge shows both local minimum and local maximum volume depending on dosage of inorganic flocculant. From these results, variations of polymer flocculant morphology under various inorganic flocculant dosages are discussed. A procedure for determining the optimum composition of a composite dry powdered flocculant for turbidity removal is proposed.

Attempts to gain an insight and present bacterial growth pattern from OVAT perspectives are quite defective and strenuous. The present study aimed at evaluating this concept from the different perspective by evaluating factors with more impacts on the growth of a mesophilic bacterium, Bacillus cereus (ATCC 14579) in a batch type medium of orbital shake flasks. Screening of linear and interactions effects of parametric markers was evaluated by two level (24) factorial design of experiment (DOE). Growth was found to respond significantly to nutrient concentration coupled with other independent variables. The factorial models established from experimental design to investigate the individual and interactions effects toward the response within the selected variables of nutrient concentration (4-16g l-1), temperature (30 oC –42 oC), agitation (140 rpm-200 rpm) and acclimatization time (24 hours-72 hours). These were statistically validated using analysis of variance (ANOVA). The results revealed that the model terms were all significant with F-value of 251.07 at (p=0.004). The model term having the most significant effect on the response was nutrient concentration. And the magnitude of the influence is in the ascending order A > B> AB > C > AC. Based on the R2 and adjusted R2 the estimated model terms spell high degree of relationship between observed and predicted values, thus the prediction ability of the mo dels is maintained. It could, therefore, be concluded that nutrient concentration, temperature and acclimatization time were variables that greatly limit growth at a specific range.

This study investigates the utility of a hybrid adsorption-membrane process for cake compressibility evaluation of biotreated palm oil mill effluent (BPOME). A low-cost empty fruit bunch (EFB) based powdered activated carbon (PAC) was employed for the upstream adsorption process with operation conditions of 60 g/L PAC dose, 68 min mixing time, and 200 rpm mixing speed to reduce the feed-water strength and alleviate probable fouling of the membranes. Two polyethersulfone microfiltration (MF) membranes of 0.1 and 0.2 μm pore sizes were investigated under constant transmembrane pressures (TMP) of 40, 80, and 120 kPa. The compressibility factors (z), which was obtained from the slopes of power plots (function of specific cake resistance (α) and pressure gradient) were evaluated. The z values of 0.32 and 0.52, respectively obtained, for the 0.1 and 0.2 μm MF membranes provided compressible and stable z values as observed from their power plots. Besides, these membranes were found suitable for the measurement of z since the results are in consonance with the established principle of cake compressibility. Moreover, the upstream adsorption mitigated the clogging of the membranes which ultimately led to moderate resistances and cake compressibility. These are indications that with the secondary cake filtration, a sustainable flux can be achieved during BPOME filtration. The membranes exhibited close to 100% restoration after cleaning.

Inhibitory effects of hydrogen sulfide could either be due to toxicity to living tissue or precipitation of sulfide salts which inhibit its utilization for cell growth. Growth, is undoubtedly affected by certain conditions, among which are nutrient types and availability, as well as the operational parameters of the fermenting medium. In this study, Bacillus cereus (ATCC 14579) was tested for potential sulfide biodegradation in a suspended growth medium of orbital shake flasks using a single milieu composition under defined operational parameters. Growth and sulfide oxidation efficiency were measured spectrophotometrically under optimum physical conditions of pH, temperature, acclimatization time and agitation. Sulfide reduction was overwhelmingly recorded at three different sulfide loading rates of 200 ppm S2- L-1 d- 1, 300 ppm S2- L-1 d-1 and 500 ppm S2- L-1 d-1 with corresponding appreciable cell growth measured at OD600 nm. Results indicated that it was possible to realise sulfide removal efficiency of 95% to 99% using this strain in an orbital shake flask within 24 hrs, as well as 65% to 78% within the first 6 hrs of inoculation. Overall, sulfide wasreduced by 95% in 200 ppm and 300 ppm, while 99% in 500 ppm, respectively. While, the corresponding exponential cell growth recorded was 3.91, 3.80 and 3.61 in 200 ppm, 300 ppm and 500 ppm, respectively. This also translate to cell biomass synthesis (cell dry weight) of 0.61 g/L, 0.58 g/L and 0.50 g/L in 200 ppm, 500 ppm and 300 ppm. Based on this finding, it was clear that this inoculum can utilize different sulfide concentration for growth and biosynthesis; thus can be employed to treat sulfide contaminated wastewater in a suspended growth form under simple nutrient composition and operational conditions.

Optimization of Ultrasound-assisted extraction parameters is necessary to determine the optimum level of the parameters, including solvent-to-material ratio, power, extraction time, solvent concentration, temperature, and pH. This review focuses on the UAE parameters’ effects on the antioxidant activity, their interactions, and the best method of examining antioxidant activity to respond to the UAE’s optimization. It was determined that the optimal extraction time is 15 minutes, and any duration longer than that could result in reduction of antioxidant activity. The temperature effect is important, wherein antioxidant activity decreases significantly when the extraction temperature is higher than 45 °C. Increasing the solvent concentration beyond 50% decreased the antioxidant activity. No increase in antioxidant activity was observed with a solvent/sample ratio greater than 40 ml/g. Increased ultrasound power leads to increased antioxidant compounds, especially in the range of ultrasound power, such as 50 to 150 W. However, higher ultrasound power creates free hydroxyl radicals that destroy the antioxidant compound. With an increase in pH, the radical scavenging activity increases significantly. It should, however, be at a near-neutral level, such as pH 6. Comparative literature has shown that optimizing UAE contributes to enhanced antioxidant activity and enhances resource conservation, such as energy and chemicals.

In the expression process of slurry material using a filter-press of compression type, the process is divided into two periods: the filtration period and the consolidation period. Identification of the exact time of the culmination of filtration period is essential for operating the press effectively. This study focused on the electrokinetic phenomena during expression operation of zinc oxide slurry to obtain information on the status of the filter chamber. We have measured the time course of electrical potential difference (EPD) between both ends of expressed material during the expression process using a laboratory piston press. The absolute value of EPD increased with the progress of the filtration period, followed by the decrease during the consolidation period. It was observed that the time at which the absolute value of the EPD began to decline coincided with the time at which the filtration period ended. EPD reached the plateau value at the end of consolidation. In a consolidation of homogeneous semisolid material, the absolute value of EPD increased at the beginning of the operation, followed by the decline to the plateau value. We have extended the theoretical equation of streaming potential for a straight capillary to be applied to a tortuous flow path of the expressed material. The time course of EPD can be qualitatively explained by using the proposed equation for EPD and calculated liquid pressure distributions based on the conventional filtration and consolidation theories by considering the medium resistance.

An integrated low-cost adsorption (with powdered activated carbon, PAC) and cross-flow membrane filtration (with microfiltration membranes of 0.1 and 0.2 μm pore sizes) process was employed for the treatment of biotreated palm oil mill effluent (POME) to produce irrigation water that is fully benchmarked with water-quality standards. The permeate quality was within the recommended standard for irrigation water, as the concentrations of all critical constituents were well below their recommended values. Sustainability of the process integration was further confirmed with the domination of cake filtration over other blocking mechanisms with higher R2 values at all trans-membrane pressures. Suitable extended usage of permeate was found for toilet/urinal flushing.

Availability of quality-certified water is pertinent to the production of food and pharmaceutical products. Adverse effects of manganese content of water on the corrosion of vessels and reactors necessitate that process water is scrutinized for allowable concentration levels before being applied in the production processes. In this research, optimization of the adsorption process conditions germane to the removal of manganese from biotreated palm oil mill effluent (BPOME) using zeolite 3A subsequent to a comparative adsorption with clinoptilolite was studied. A face-centered central composite design (FCCCD) of the response surface methodology (RSM) was adopted for the study. Analysis of variance (ANOVA) for response surface quadratic model revealed that the model was significant with dosage and agitation speed connoting the main significant process factors for the optimization. R(2) of 0.9478 yielded by the model was in agreement with predicted R(2). Langmuir and pseudo-second-order suggest the adsorption mechanism involved monolayer adsorption and cation exchanging.

Flocculation is a widely used process for particle removal in water/wastewater treatment. Clarification method by using composite flocculants in powder form has been proposed in the literature. Such composite flocculants are conveniently used in the flocculation process of small volume suspensions. In this study, fundamental aspects of the clarification mechanism of the composite dry powdered flocculant are investigated. 1.00 mg/mL suspension of polymethyl methacrylate particle (PMMA, 0.15 μm in diameter) is used as a colloidal material. A model composite flocculant comprising an inorganic flocculant (aluminum sulfate), anionic polymer flocculant (copolymer of acrylic acid and acrylic amide), and a flocculation aid (calcium carbonate ) is studied. The effects of each component on turbidity removal are examined. It is clarified that the order of addition, the state of polymer flocculant (powdered form or liquid form), and combination of components (polymer flocculant with/without aid particles) are critical for turbidity removal with combined use of flocculation aid, inorganic flocculant and polymer flocculant. When the composite dry powdered flocculant is added to a colloidal suspension, the inorganic flocculant dissolves immediately. The polymer flocculant particles disperse well in the suspension with the help of flocculation aid particles and dissolve moderately. The ions from inorganic flocculant result in formation of microflocs composed of both PMMA and flocculation aid particles. Flocculation aid particles play an important role; i.e. they accelerate flocculation of PMMA particles and attenuate the ability of the polymer flocculant particles to produce undissolved lumps.

Significant attention has been given to biogas production, purification and upgrading as a renewable and clean fuel supplement. Biogas is a product of an anaerobic digestion process comprising methane, carbon dioxide, and trace amounts of other gases. Biogas purification removes trace gases in biogas for safe utilisation. Biogas upgrading produces methane-rich biogas by removing bulk carbon dioxide from the gas mixture. Several carbon dioxide removal techniques can be applied for biogas upgrading. However, chemical absorption of carbon dioxide for biogas upgrading is of special significance due to its operation at ambient or near ambient temperature and pressure, thus reducing energy consumption. This paper reviews the chemical absorption of carbon dioxide using amine scrubbing, caustic solvent scrubbing, and amino acid salt solution scrubbing. Each of these techniques for biogas upgrading is discussed. The paper concludes that an optimised implementation of the chemical absorption techniques for biogas upgrading requires further research.

Electrocoagulation (EC) is a popular wastewater treatment alternative that had been studied extensively for a wide range of wastewater types, due to its versatility, ease of setup, low footprint and eco-friendly nature. The recent studies on EC advancements on various wastewater types had been reviewed in this paper. The operational variables that are vital to EC and the fundamental relationship of EC with conventional chemical coagulation had been assessed as they are the primary factors that govern the pollutant removal mechanism of the process. Hence, EC needs further studies for optimisation of its process parameters and modelling for scale up in the industrial level. Moreover, this paper reviews the current emerging hybrid technologies of EC with integrated separation technologies and their limitations for enhanced wastewater treatment systems for cleaner effluents, water reclamation and recycle. The current prominent hybrid EC processes under research include: EC-adsorption, EC-peroxidation, EC-chemical coagulation (CC), photovoltaic EC and EC-membrane. Due to the overall low footprint requirement, environmental sustainability and strong potential of constant operation without needing extensive control, hybrid EC-membrane process undeniably stands out to be the future of wastewater treatment.

Despite the widely documented excellent purification capacity of membranes, their main drawback—fouling—is still being extensively researched with a view to finding a sustainable solution. Fouling simply implies the process that results in the performance loss of a membrane due to the deposition of suspended or dissolved matters onto its external surface or the internal pore walls [1]. Fouling eventually leads to a reduction in the active area of the membrane and thereby results in a reduction in flux below the theoretical capacity of the membrane. Fouling or pore-blocking has been identified as the main reason limiting the adoption of membrane purification processes by many industries. Consequently, an apt understanding of the pore-blocking mechanisms of membranes is imperative, as it is a pertinent factor dictating the overall performance of the filtration process. Pore blockage can occur in any of the two commonly known membrane operations: constant-pressure and constant-flux rate. In a constant-pressure operation, pore blockage usually leads to a sharp decline in permeate flux, while a severe pressure rise is usually encountered in a constant-flux rate operation. In principle, governing filtration models can facilitate the design of membrane processes more than any experiment or characterization can, yet data from experiments are usually required for validation purposes [2–5]. To properly control particulate fouling at the design stage, as well as appropriately monitor it during a plant operation, the methods utilized in evaluating the particulate content of feed-water in predicting membrane fouling are crucial. Soluble and colloidal materials are assumed to be responsible for membrane pore blockage, while suspended solids are mainly accountable for the cake layer resistance [4,6,7]. To accurately measure and predict particulate fouling, it is recommended that specific fouling mechanisms/indices be investigated with respect to specific membranes since the Modified Fouling Index (MFI), where a 0.45 μm membrane filter is used and usually represented as MFI0.45, cannot represent all membrane types. This is due to the fact that some principal parameters such as retention of smaller particulates, the nature and concentration of solutes and solvents, proof of cake filtration, pore size distribution, surface morphology, module hydrodynamics and membrane type/material must be considered in such investigations [1,8]. Therefore, in any proposed membrane process with plans for sustainability, pore-blocking modeling is germane for the determination of some key factors necessary for the design of an efficient membrane system. These factors are: (1) the description of the extent of membrane fouling in terms of particle accumulation at the membrane surface or inside the membrane pores; (2) the prediction of the fouling potential of a specific feed with respect to a specific membrane; and (3) the identification of the most appropriate and sustainable cleaning method necessary for the membrane process. In this study, a systemic investigation was carried out on high-strength agro-industrial wastewater to describe the successive steps involved in the flux decline of a membrane filtration process in terms of pore-blocking mechanism. Microfiltration (MF) and ultrafiltration (UF) membranes, which are the popular low-pressure membranes (LPMs), were utilized for the filtration of the high-strength wastewater. The wastewater is specifically a discharge of an end-of-pipe treatment process from the agro-industry palm oil milling process. An upstream adsorption process was applied to lower the feed strength and reduce its fouling effects on the membranes. The investigative experiments were conducted in a constant-pressure and cross-flow filtration mode through polyethersulfone (PES) MF (pore sizes: 0.1 and 0.2 μm) and UF (molecular weight cut-off: 1, 5 and 10 kDa) membranes at the transmembrane pressures of 40, 80 and 120 kPa. The examined results within the frame of the common blocking mechanisms revealed that the blocking index, η, decreased from 2 to 0 in all five membranes. The pore-blocking phenomenon was successively observed from the complete blocking mechanism (i.e., η = 2) down to the cake filtration mechanism (i.e., η = 0). Furthermore, there is an indication that the early blockage of the pores and formation of a cake resulted in a limiting cake height evident from the near-constant trend of the permeate flux. This means that cake filtration could be best used to explain the fouling mechanisms of the feed on the LPMs based 139Modeling of Pore-Blocking Behaviors of Low-Pressure Membranes on the coefficient of determination (R2) values at all applied pressures. This further demonstrates that the fouling is primarily caused by the gradual reversible cake deposition, which could be easily removed by less onerous cleaning methods.

Electroforced sedimentation (EFS) is a well-known technique for enhancing the solid content of the final sludge cake. However, the parameters affecting the performance of EFS and quality of the resulting sludge cake, as well as the removed water, are not sufficiently studied. In this research, a mixture of zinc oxide (representing sludge) and polyacrylamide (dewatering aid) were used as experimental materials. The process parameters of electroforced sedimentation were optimized using a design of experiment software (Design Expert ® Version 7.0.0) with a face-centered central composite design (FCCCD) under response surface methodology. An optimization study was carried out for the output response (sedimentation velocity) based on three process factors and an empirical model was developed. The optimized values for current density, total solid volume per unit cross-sectional area and polyacrylamide dose for the highest sedimentation velocity (0.0199 cm/min) were 6.0 A/m2, 7.74 mm and 1.53 % (based on the weight of zinc oxide), respectively. The overall model was significant with Prob > F value of 0.0117 and R 2 value of 0.8911 while the most significant parameter was observed to be the current density with a Prob > F value of 0.0004. Validation experiments were conducted to confirm and measure the accuracy of the models for the three set of parameters including optimum parameters. The error was within the limit of prediction accuracy, and the sedimentation velocity was enhanced by the addition of 1.53 % PAM as dewatering aid. Thus, it was concluded that EFS can be applied successfully for materials having permanent charge.

Electroosmosis is especially effective in removing liquid from a highly compressible difficult-to-filter solid/liquid mixture. The extent of solid/liquid separation depends on the electroosmotic pressure gradient (Epg) which is a combination of applied electric field, the surface charge density of solid particles and the flow path structure in the mixture. The larger the Epg value, the higher the solid content of the treated mixture. A theoretical equation of Epg for a capillary flow is derived from the Navier–Stokes equation, and its extensions to a flow through porous materials are examined by using experimental Epg values from constant-current electroosmotic dewatering (EOD), electroosmotic permeation (EOP) and electro-forced sedimentation (EFS) tests. It has been clarified that the specific hydrodynamic resistance α has the most effect on the Epg value. The larger the α value of the material, the larger its Epg value. Modifications to the existing theories were suggested to understand the effect of solid/liquid mixture concentration on the separation under electric field more precisely.

This study focused on the production of a novel multi-CLEA comprising the enzyme activities of lipase and protease from fish viscera. A multi-CLEA is a single biocatalyst that can catalyze separate unrelated reactions, but these reactions can be conducted in one application. Tests pertaining to the effect of various additives on the multi-CLEA’s activity were performed. Response Surface Methodology’s Face Centered Central Composite Design (FCCCD) was employed to optimize the preparation parameters of the multi-CLEA in an aqueous medium. It was found that 55% (w/v) of ammonium sulfate, 65 mM of glutaraldehyde, and 0.113 mM of bovine serum albumin were the optimum levels of additives to prepare the multi-CLEA with the protease and lipase recovery activity of 43.82% and 99.91%, respectively. Multi-CLEAs were found to retain an average of more than 34% of the initial activity after five consecutive batches for both enzymes. Finally, the multi-CLEA was utilized to catalyze two reactions: improved washing process and biodiesel production. The stain removal percentage of a commercial detergent was improved by 67.78% after adding multi-CLEA. In addition, the multi-CLEA catalyzed biodiesel production from vegetable oil with a percentage conversion of 51.7%. Such results demonstrated that the multi-CLEA is a promising catalyst for biotechnological applications.

Biosorption of chemical oxygen demand (COD), manganese (Mn) and hydrogen sulphide (H2S) onto an empty fruit bunch (EFB)–based powdered activated carbon (PAC) from a multicomponent system—biotreated palm oil mill effluent (BPOME)—were studied in a batch adsorption process. The experimental results were fitted to four isotherm models, and four kinetic models. Amongst the isotherm models (Langmuir, Freundlich, Temkin and Dubinin-Radushkevich) employed, Langmuir model showed the best conformity to the equilibrium data with R 2 values of 1.00 for COD and 0.9999 for both Mn and H2S. The Dubinin–Radushkevich model followed the conformity trend with R 2 values of 0.9984, 0.9948 and 0.9824 for COD, H2S, and Mn, respectively. Also, amongst the kinetic models (Pseudo-first order, Lagergren’s pseudo-second order, Elovich and Weber–Morris intra-particle diffusion) employed, only the pseudo-second order model could best describe the adsorption behaviours of all the three contaminants with R 2 values of 1.00 in all cases. The mechanistic uptake pathway was further examined by means of the Fourier transform infrared in studying the surface chemistry of the PAC. It was observed that the presence of functional groups like the aldehydes and ketones, carbonyl, mono-alkyl, amines, amongst others led to physicochemical interactions between PAC surface and the contaminants. Overall, the equilibrium, kinetics and surface chemistry analyses pointed towards the adsorption processes been largely driven by electrostatic sorption. Additionally, the EFB-based PAC was capable of reducing COD, Mn and H2S from POME, hence, could be utilized in developing a unit operation for integration into the current POME treatment. Percent uptake versus adsorption time plot for COD, Mn and H2S removal from biotreated POME.

Face centered central composite design was used to optimize the enzyme loading, reaction temperature and mixing speed of sludge palm oil (SPO) transesterification reaction using locally produced Candida cylindracea lipase. The developed quadratic model was found to be significant at p < 0.05. The highest biodiesel yield of 57.5 % (w/w SPO) and 15.22 % free fatty acids (FFA) conversion to biodiesel with coefficient of determination R2 of 0.91 and 0.93, respectively were obtained at enzyme loading of 0.4 U/g SPO, 41 °C and 250 rpm mixing speed. Enzyme loading (U/g) gave little effect on the %FFA conversion to biodiesel and total biodiesel yield compared to temperature and mixing speed due to high FFA and water content, thus further studies are required for improvement. The study shows the low cost SPO and locally produced lipase have a promising potential in the utilization of waste for low cost biodiesel production.

In this investigation, the potential of powdered activated carbon (PAC) derived from empty fruit bunch (EFB) precursor through pyrolysis method for chemical oxygen demand (COD) adsorption from biotreated palm oil mill effluent (POME) was extensively studied. The PAC was prepared and characterized using scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy and Brunauer–Emmett–Teller. The SEM microphotographs showed opened micropores existing in the PAC structure with a surface area of 886.2 m2/g. The FTIR spectra revealed the three major peaks exhibited by the surface of the activated carbon at exactly wavenumbers of 1737.61, 1365.10 and 1216.91 cm−1. This suggests the presence of some functional groups which can potentially enhance positive interactions between the adsorbent and the adsorbate. Design-Expert ® software (version 7.0.0) was employed for the statistical experimental design of a two-step optimization: factorial and response surface methodology. Maximum COD reduction of 84 % (227 ppm residual) was achieved from an initial concentration of 1387 ppm. This study being the first optimization process with the utility of EFB-based PAC in the treatment of the high-strength multicomponent biotreated POME; hence, the results could serve as requisite data for upscaling and/or future investigations in the utility of the precursor as a viable adsorbent.