Malaysia is the world’s top manufacturer of examination and surgical natural rubber (NR) gloves, exported mainly to the USA and Europe. The glove manufacturing process yields effluent which must be treated to comply with the stringent regulatory requirements imposed by the Malaysian Department of Environment. To make glove manufacturing an eco-friendly process, efforts are geared towards minimizing and utilizing waste or converting it into raw material for making value-added products. Waste generated from the glove industry is mainly rubber sludge which is obtained from the chemical flocculation stage of the effluent treatment process and consists of mainly rubber, remnants of compounding ingredients and water. R&D work by the Malaysian Rubber Board on waste utilization and resource recovery investigations have revealed many uses for this sludge. This paper briefly outlines only one of the many options available, which is the conversion of the sludge into sludge derived fuel (SDF). Preliminary study has identified three formulations of SDF with calorific values (CV) exceeding 16 000 kJ/kg, matching a good grade coal. This was considered as promising results which warrant explorative work for further increasing the CV of SDF to turn it into a viable fuel substitute in the latex products manufacturing industry and subsequently apply for a Clean Development Mechanism status to generate income.
In this work, the feasibility of coagulation-flocculation coupled with UV-based sulfate radical oxidation process (UV/SRAOP) in the removal of chemical oxygen demand (COD) of stabilized landfill leachate (SLL) was evaluated. For coagulation-flocculation, ferric chloride (FeCl3) was used as the coagulant. The effect of initial pH of SLL and COD:FeCl3 ratio on the COD removal was evaluated. The result revealed that COD:FeCl3 ratio of 1:1.3 effectively removed 76.9% of COD at pH 6. The pre-treated SLL was then subjected to UV/SRAOP treatment. For UV/SRAOP, the sulfate radical (SR) was generated using UV-activated persulfate (UV/PS) and peroxymonosulfate (UV/PMS). The dosage of oxidant and reaction time were found to be the main parameters that influence the efficiency of COD removal. On the other hand, the effect of initial pH (3-7) and the type of oxidant (PS and PMS) was found to have no significant influence on COD removal efficiency. At optimum conditions, approximately 90.9 and 91.5% of COD was successfully removed by coagulation-flocculation coupled with UV/PS and UV/PMS system, respectively. Ecotoxicity study using zebrafish showed a reduction in toxicity of SLL from 10.1 to 1.74 toxicity unit (TU) after coagulation-flocculation. The TU remained unchanged after UV/PS treatment but slightly increased to 1.80 after UV/PMS treatment due to the presence of residual sulfate ion in the treated effluent. In general, it can be concluded that coagulation-flocculation coupled with UV/SRAOP could be a potential water treatment method for SLL treatment.
Fish oil-in-water emulsions containing fish oil, thiol-modified β-lactoglobulin (β-LG) fibrils, chitosan and maltodextrin were fabricated using a high-energy method. The results showed that chitosan coating induced charge reversal; denoting successful biopolymers complexation. A significantly (p<0.05) larger droplet size and lower polydispersity index value, attributed to the thicker chitosan coating at the oil-water interface, were observed. At high chitosan concentrations, the cationic nature of chitosan strengthened the electrostatic repulsion between the droplets, thus conferring high oxidative stability and low turbidity loss rate to the emulsions. The apparent viscosity of emulsions stabilized using thiol-modified β-LG fibrils-chitosan complex was higher than those stabilized using β-LG fibrils alone, resulting in the former's higher creaming stability. Under thermal treatments (63°C and 100°C), emulsions stabilized using thiol-modified β-LG fibrils-chitosan complex possessed higher heat stability as indicated by the consistent droplet sizes observed. Chitosan provided a thicker protective layer that protected the oil droplets against high temperature. Bridging flocculation occurred at low chitosan concentration (0.1%, w/w), as revealed through microscopic observations which indicated the presence of large flocs. All in all, this work provided us with a better understanding of the application of protein fibrils-polysaccharide complex to produce stable emulsion.
The utilization of metal-based conventional coagulants/flocculants to remove suspended solids from drinking water and wastewater is currently leading to new concerns. Alarming issues related to the prolonged effects on human health and further pollution to aquatic environments from the generated nonbiodegradable sludge are becoming trending topics. The utilization of biocoagulants/bioflocculants does not produce chemical residue in the effluent and creates nonharmful, biodegradable sludge. The conventional coagulation-flocculation processes in drinking water and wastewater treatment, including the health and environmental issues related to the utilization of metal-based coagulants/flocculants during the processes, are discussed in this paper. As a counterpoint, the development of biocoagulants/bioflocculants for drinking water and wastewater treatment is intensively reviewed. The characterization, origin, potential sources, and application of this green technology are critically reviewed. This review paper also provides a thorough discussion on the challenges and opportunities regarding the further utilization and application of biocoagulants/bioflocculants in water and wastewater treatment, including the importance of the selection of raw materials, the simplification of extraction processes, the application to different water and wastewater characteristics, the scaling up of this technology to a real industrial scale, and also the potential for sludge recovery by utilizing biocoagulants/bioflocculants in water/wastewater treatment.
Nowadays, the pretreatment of wastewater prior to discharge is very important in various industries as the wastewater without any treatment contains high organic pollution loads that would pollute the receiving waterbody and potentially cause eutrophication and oxygen depletion to aquatic life. The reuse of seafood wastewater discharge in microalgae cultivation offers beneficial purposes such as reduced processing cost for wastewater treatment, replenishing ground water basin as well as financial savings for microalgae cultivation. In this paper, the cultivation of Chlorella vulgaris with an initial concentration of 0.01 ± 0.001 g⋅L-1 using seafood sewage discharge under sunlight and fluorescent illumination was investigated in laboratory-scale without adjusting mineral nutrients and pH. The ability of nutrient removal under different lighting conditions, the metabolism of C. vulgaris and new medium as well as the occurrence of auto-flocculation of microalgae biomass were evaluated for 14 days. The results showed that different illumination sources did not influence the microalgae growth, chemical oxygen demand (COD) and biochemical oxygen demand (BOD) significantly. However, the total nitrogen (total-N) and total phosphorus (total-P) contents of microalgae were sensitive to the illumination mode. The amount of COD, BOD, total-N and total-P were decreased by 88%, 81%, 95%, and 83% under sunlight mode and 81%, 74%, 79%, and 72% under fluorescent illumination, respectively. Furthermore, microalgae were auto-flocculated at the final days of cultivation with maximum biomass concentration of 0.49 ± 0.01 g⋅L-1, and the pH value had increased to pH 9.8 ± 0.1 under sunlight illumination.
The natural coagulant Moringa oleifera lectin (MoL) as cationic protein is a promising candidate in coagulation process of water treatment plant. Introducing the gene encoding MoL into a host, Pichia pastoris, to secrete soluble recombinant protein is assessed in this study. Initial screening using PCR confirmed the insertion of MoL gene, and SDS-PAGE analysis detected the MoL protein at 8 kDa. Cultured optimization showed the highest MoL protein at 520 mg/L was observed at 28 °C for 144 h of culturing by induction in 1% methanol. Approximately, 0.40 mg/mL of recombinant MoL protein showed 95 ± 2% turbidity removal of 1% kaolin suspension. In 0.1% kaolin suspension, the concentration of MoL at 10 μg/mL exhibits the highest turbidity reduction at 68 ± 1%. Thus, recombinant MoL protein from P. pastoris is an effective coagulant for water treatment.
This study evaluated the potential of bioflocculant production from Aspergillus niger using palm oil mill effluent (POME) as carbon source. The bioflocculant named PM-5 produced by A. niger showed a good flocculating capability and flocculating rate of 76.8% to kaolin suspension could be achieved at 60 h of culture time. Glutamic acid was the most favorable nitrogen source for A. niger in bioflocculant production at pH 6 and temperature 35 °C. The chemical composition of purified PM-5 was mainly carbohydrate and protein with 66.8% and 31.4%, respectively. Results showed the novel bioflocculant (PM-5) had high potential to treat river water from colloids and 63% of turbidity removal with the present of Ca(2+) ion.
The bacterial reduction of Cr(VI) from industrial wastewater was evaluated using a 2.0-m(3) bioreactor. Liquid pineapple waste was used as a nutrient for the biofilm community formed inside the bioreactor. The use of rubber wood sawdust as packing material was able to immobilize more than 10(6) CFU mL(-1) of Acinetobacter haemolyticus cells after 3 days of contact time. Complete reduction of 15-240 mg L(-1) of Cr(VI) was achieved even after 3 months of bioreactor operation. Cr(VI) was not detected in the final effluent fraction indicating complete removal of Cr from solution from the flocculation/coagulation step and the unlikely re-oxidation of Cr(III) into Cr(VI). Impatiens balsamina L. and Gomphrena globosa L. showed better growth in the presence of soil-sludge mixture compared to Coleus scutellarioides (L.) Benth. Significant amounts of Cr accumulated at different sections of the plants indicate its potential application in Cr phytoremediation effort. The bacterial-based system was also determined not to be detrimental to human health based on the low levels of Cr detected in the hair and nail samples of the plant operators. Thus, it can be said that bacterial-based Cr(VI) treatment system is a feasible alternative to the conventional system especially for lower Cr(VI) concentrations, where sludge generated can be used as growth supplement for ornamental plant as well as not detrimental to the health of the workers.
The removal of Reactive Black 5 dye in an aqueous solution by electrocoagulation (EC) as well as addition of flocculant was investigated. The effect of operational parameters, i.e. current density, treatment time, solution conductivity and polymer dosage, was investigated. Two models, namely the artificial neural network (ANN) and the response surface method (RSM), were used to model the effect of independent variables on percentage of dye removal. The findings of this work showed that current density, treatment time and dosage of polymer had the most significant effect on percentage of dye removal (p<0.001). In addition, interaction between time and current density, time and dosage of polymer, current density and dosage of polymer also significantly affected the percentage of dye removal (p=0.034, 0.003 and 0.024, respectively). It was shown that both the ANN and RSM models were able to predict well the experimental results (R(2)>0.8).
The enzymatic reduction of Cr(VI) to Cr(III) by Cr(VI) resistant bacteria followed by chemical precipitation constitutes the ChromeBac system. Acinetobacter haemolyticus was immobilized onto carrier material inside a 0.2m(3) bioreactor. Neutralized electroplating wastewater with Cr(VI) concentration of 17-81 mg L(-1) was fed into the bioreactor (0.11-0.33 m(3)h(-1)). Complete Cr(VI) reduction to Cr(III) was obtained immediately after the start of bioreactor operation. Together with the flocculation, coagulation and filtration, outflow concentration of less than 0.02 mg Cr(VI)L(-1) and 1mg total CrL(-1) were always obtained. Performance of the bioreactor was not affected by fluctuations in pH (6.2-8.4), Cr(VI) (17-81 mg L(-1)), nutrient (liquid pineapple waste, 1-20%v/v) and temperature (30-38 degrees C). Standby periods of up to 10 days can be tolerated without loss in activity. A robust yet effective biotechnology to remove chromium from wastewater is thus demonstrated.
The performance of pectin in turbidity reduction and the optimum condition were determined using Response Surface Methodology (RSM). The effect of pH, cation's concentration, and pectin's dosage on flocculating activity and turbidity reduction was investigated at three levels and optimized by using Box-Behnken Design (BBD). Coagulation and flocculation process were assessed with a standard jar test procedure with rapid and slow mixing of a kaolin suspension (aluminium silicate), at 150 rpm and 30 rpm, respectively, in which a cation e.g. Al(3+), acts as coagulant, and pectin acts as the flocculant. In this research, all factors exhibited significant effect on flocculating activity and turbidity reduction. The experimental data and model predictions well agreed. From the 3D response surface graph, maximum flocculating activity and turbidity reduction are in the region of pH greater than 3, cation concentration greater than 0.5 mM, and pectin dosage greater than 20 mg/L, using synthetic turbid wastewater within the range. The flocculating activity for pectin and turbidity reduction in wastewater is at 99%.
Microbial flocs formed from raw textile wastewater in a prototype Aerobic Biofilm Reactor (ABR) system were characterised and studied for their potential use in the treatment of textile wastewater. After 90-100 days of operation, microbial flocs of loose irregular structures were obtained from the reactor with good settling velocity of 33 m/h and sludge volume index (SVI) of 48.2 mL/g. Molecular analysis of the flocs using PCR-amplified 16S rDNA sequence showed 98% homology to those of Bacillus sp, Paenibacillus sp and Acromobacter sp. Detection of Ca(2+)(131 mg/g) and Fe(2+)(131 mg/g) using atomic absorption spectrometer might be implicated with the flocs formation. In addition, presence of Co(2+) and Ni(2+) were indicative of the flocs ability to accumulate at least a fraction of the metals' present in the wastewater. When the flocs were used for the treatment of raw textile wastewater, they showed good removal of COD and colour about 55% and 70% respectively, indicating their potential application.
Coagulation-flocculation is a relatively simple physical-chemical technique in treatment of old and stabilized leachate which has been practiced using a variety of conventional coagulants. Polymeric forms of metal coagulants which are increasingly applied in water treatment are not well documented in leachate treatment. In this research, capability of poly-aluminum chloride (PAC) in the treatment of stabilized leachate from Pulau Burung Landfill Site (PBLS), Penang, Malaysia was studied. The removal efficiencies for chemical oxygen demand (COD), turbidity, color and total suspended solid (TSS) obtained using PAC were compared with those obtained using alum as a conventional coagulant. Central composite design (CCD) and response surface method (RSM) were applied to optimize the operating variables viz. coagulant dosage and pH. Quadratic models developed for the four responses (COD, turbidity, color and TSS) studied indicated the optimum conditions to be PAC dosage of 2g/L at pH 7.5 and alum dosage of 9.5 g/L at pH 7. The experimental data and model predictions agreed well. COD, turbidity, color and TSS removal efficiencies of 43.1, 94.0, 90.7, and 92.2% for PAC, and 62.8, 88.4, 86.4, and 90.1% for alum were demonstrated.
Suspended solids, colour and chemical oxygen demand (COD) are among the main pollutants in landfill leachate. Application of physical or biological processes alone is normally not sufficient to remove these constituents, especially for leachate with a lower biochemical oxygen demand (BOD)/ COD ratio. The main objective of this research was to investigate the efficiency of coagulation and flocculation processes for removing suspended solids, colour and COD from leachate produced in a semi-aerobic landfill in Penang, Malaysia. A 12-month characterization study of the leachate indicated that it had a mean annual BOD/COD ratio of 0.15 and was partially stabilized, with little further biological degradation likely to occur. Particle size analysis of the raw leachate indicated that its 50th percentile (d50) was 11.68 microm. Three types of coagulants were examined in bench scale jar test studies: aluminium sulphate (alum), ferric chloride (FeCl3) and ferrous sulphate (FeSO4). The effects of agitation speed, settling time, pH, coagulant dosages and temperature were examined. At 300 rpm of rapid mixing, 50 rpm of slow mixing, and 60 min settling time, higher removals of suspended solids (over 95%), colour (90%) and COD (43%) were achieved at pH 4 and 12. FeCl3 was found to be superior to other coagulants tested. At pH 4 and 12, fair removal of suspended solids was observed at a reasonably low coagulant dose, i.e., 600 mg L(-1); hHowever, about 2500 mg L(-1) of coagulant was required to achieve good removals at pH 6. Better removals were achieved at higher temperature. The d50 of sludge after coagulation at pH 4 with a 2500 mg L(-1) FeCl3 dose was 60.16 microm, which indicated that the particles had been removed effectively from the leachate. The results indicate that coagulation and flocculation processes can be used effectively in integrated semi-aerobic leachate treatment systems, especially for removing suspended solids, colour and COD.
Moringa oleifera seeds, an environmental friendly and natural coagulant are reported for the pretreatment of palm oil mill effluent (POME). In coagulation-flocculation process, the M. oleifera seeds after oil extraction (MOAE) are an effective coagulant with the removal of 95% suspended solids and 52.2% reduction in the chemical oxygen demand (COD). The combination of MOAE with flocculant (NALCO 7751), the suspended solids removal increased to 99.3% and COD reduction was 52.5%. The coagulation-flocculation process at the temperature of 30 degrees C resulted in better suspended solids removal and COD reduction compared to the temperature of 40, 55 and 70 degrees C. The MOAE combined with flocculant (NALCO 7751) reduced the sludge volume index (SVI) to 210mL/g with higher recovery of dry mass of sludge (87.25%) and water (50.3%).
The production and characterization of a bioflocculant, IH-7, by Aspergillus flavus was investigated. About 0.4 g of purified bioflocculant with an average molecular weight of 2.574 × 10(4)Da could be obtained from 1L of fermentation medium. The bioflocculant mainly consisted of protein (28.5%) and sugar (69.7%), including 40% of neutral sugar, 2.48% of uronic acid and 1.8% amino sugar. The neutral sugar components are sucrose, lactose, glucose, xylose, galactose, mannose and fructose at a molar ratio of 2.4:4.4:4.1:5.8:9.9:0.8:3.1. Fourier-transform infrared spectroscopy analysis revealed that purified IH-7 contained hydroxyl, amide, carboxyl and methoxyl groups. The elemental analysis of purified IH-7 showed that the weight fractions of the elements C, H, O, N and S were 29.9%, 4.8%, 34.7%, 3.3%, and 2.0%, respectively. IH-7 had good flocculating rate in kaolin suspension without cation addition and stable over wide range of pH and temperature.
The coagulation-flocculation process incorporated with membrane separation technology will become a new approach for palm oil mill effluent (POME) treatment as well as water reclamation and reuse. In our current research, a membrane pilot plant has been used for POME treatment where the coagulation-flocculation process plays an important role as a pretreatment process for the mitigation of membrane fouling problems. The pretreated POME with low turbidity values and high water recovery are the main objectives to be achieved through the coagulation-flocculation process. Therefore, treatment optimization to serve these purposes was performed using jar tests and applying a response surface methodology (RSM) to the results. A 2(3) full-factorial central composite design (CCD) was chosen to explain the effect and interaction of three factors: coagulant dosage, flocculent dosage, and pH. The CCD is successfully demonstrated to efficiently determine the optimized parameters, where 78% of water recovery with a 20 NTU turbidity value can be obtained at the optimum value of coagulant dosage, flocculent dosage, and pH at 15 000 mg/L, 300 mg/L, and 6, respectively.
In this study, a new, more effective and cost-effective treatment alternative is investigated for the removal of pharmaceuticals from wastewater treatment plant effluent (WWTP-eff). The potential of combining clay with biodegradable polymeric flocculants is further highlighted. Flocculation is viewed as the best method to get the optimum outcome from clay. In addition, flocculation with cationic starch increases the biodegradability and cost of the treatment. Clay is naturally abundantly available and relatively inexpensive compared to conventional adsorbents. Experimental studies were carried out with existing naturally occurring pharmaceutical concentrations found and measured in WWTP-eff with atrazine spiking for comparison between the demineralised water and WWTP-eff matrix. Around 70% of the total measured pharmaceutical compounds were removable by the clay-starch combination. The effect of clay with and without starch addition was also highlighted.
In view of green developments in water treatment, plant-based flocculants have become the focus due to their safety, degradation and renewable properties. In addition, cost and energy-saving processes are preferable. In this study, malva nut gum (MNG), a new plant-based flocculant, and its composite with Fe in water treatment using single mode mixing are demonstrated. The result presents a simplified extraction of the MNG process. MNG has a high molecular weight of 2.3 × 10⁵ kDa and a high negative charge of -58.7 mV. From the results, it is a strong anionic flocculant. Moreover, it is observed to have a branch-like surface structure. Therefore, it conforms to the surface of particles well and exhibits good performance in water treatment. In water treatment, the Fe-MNG composite treats water at pH 3.01 and requires a low concentration of Fe and MNG of 0.08 and 0.06 mg/L, respectively, when added to the system. It is concluded that for a single-stage flocculation process, physico-chemical properties such as molecular weight, charge of polymer, surface morphology, pH, concentration of cation and concentration of biopolymeric flocculant affect the flocculating performance.
The structural and hydrodynamic features for granules were characterized using settling experiments, predefined mathematical simulations and ImageJ-particle analyses. This study describes the rheological characterization of these biologically immobilized aggregates under non-Newtonian flows. The second order dimensional analysis defined as D2=1.795 for native clusters and D2=1.099 for dewatered clusters and a characteristic three-dimensional fractal dimension of 2.46 depicts that these relatively porous and differentially permeable fractals had a structural configuration in close proximity with that described for a compact sphere formed via cluster-cluster aggregation. The three-dimensional fractal dimension calculated via settling-fractal correlation, U∝l(D) to characterize immobilized granules validates the quantitative measurements used for describing its structural integrity and aggregate complexity. These results suggest that scaling relationships based on fractal geometry are vital for quantifying the effects of different laminar conditions on the aggregates' morphology and characteristics such as density, porosity, and projected surface area.