Advanced oxidation processes (AOPs) are of special interest in treating landfill leachate as they are the most promising procedures to degrade recalcitrant compounds and improve the biodegradability of wastewater. This paper aims to refresh the information base of AOPs and to discover the research gaps of AOPs in landfill leachate treatment. A brief overview of mechanisms involving in AOPs including ozone-based AOPs, hydrogen peroxide-based AOPs and persulfate-based AOPs are presented, and the parameters affecting AOPs are elaborated. Particularly, the advancement of AOPs in landfill leachate treatment is compared and discussed. Landfill leachate characterization prior to method selection and method optimization prior to treatment are necessary, as the performance and practicability of AOPs are influenced by leachate matrixes and treatment cost. More studies concerning the scavenging effects of leachate matrixes towards AOPs, as well as the persulfate-based AOPs in landfill leachate treatment, are necessary in the future.
The present study describes the phytoremediation performance of water lettuce (Pistia stratiotes L.) for physicochemical pollutants elimination from paper mill effluent (PME). For this, pot (glass aquarium) experiments were conducted using 0% (BWW: borewell water), 25%, 50%, 75%, and 100% treatments of PME under natural day/light regime. Results of the experiments showed that the highest removal of pH (10.75%), electrical conductivity (EC: 63.82%), total dissolved solids (TDS: 71.20%) biological oxygen demand (BOD: 85.03%), chemical oxygen demand (COD: 80.46%), total Kjeldahl's nitrogen (TKN: 93.03%), phosphorus (P: 85.56%), sodium (Na: 91.89%), potassium (K: 84.04%), calcium (Ca: 84.75%), and magnesium (Mg: 83.62%), most probable number (MPN: 77.63%), and standard plate count (SPC: 74.43%) was noted in 75% treatment of PME after treatment by P. stratiotes. PCA showed the best vector length for TKN, Na, and Ca. The maximum plant growth parameters including, total fresh biomass (81.30 ± 0.28 g), chlorophyll content (3.67 ± 0.05 mg g-1 f.wt), and relative growth rate (0.0051 gg-1 d-1 ) was also measured in 75% PME treatment after phytoremediation experiments. The findings of this study make useful insight into the biological management of PME through plant-based pollutant eradication while leftover biomass may be used as a feedstock for low-cost bioenergy production. PRACTITIONER POINTS: Biological treatment of paper mill effluent using water lettuce is presented. Best reduction of physicochemical and microbiological pollutants was attained in 75% treatment. Maximum production of chlorophyll, plant biomass, and highest growth rate was also observed in 75% treatment.
A sequencing batch reactor (SBR) seeded with flocculated sludge and fed with synthetic wastewater was operated for an enhanced biological phosphorus removal (EBPR) process. Eight weeks after reactor startup, sludge granules were observed. The granules had a diameter of 0.5 to 3.0 mm and were brownish in color and spherical or ellipsoidal in shape. No significant change was observed in sludge granule size when operational pH was changed from 7 to 8. The 208-day continuous operation of the SBR showed that sludge granules were stably maintained with a sludge volume index (SVI) between 30 to 55 mL/g while securing a removal efficiency of 83% for carbon and 97% for phosphorus. Fluorescent in situ hybridization (FISH) confirmed the enrichment of polyphosphate accumulating organisms (PAOs) in the SBR. The observations of sludge granulation in this study encourage further studies in the development of granules-based EBPR process.
This paper describes the design of an artificial neural network (ANN) model to predict the water quality index (WQI) using land use areas as predictors. Ten-year records of land use statistics and water quality data for Kinta River (Malaysia) were employed in the modeling process. The most accurate WQI predictions were obtained with the network architecture 7-23-1; the back propagation training algorithm; and a learning rate of 0.02. The WQI forecasts of this model had significant (p < 0.01), positive, very high correlation (ρs = 0.882) with the measured WQI values. Sensitivity analysis revealed that the relative importance of the land use classes to WQI predictions followed the order: mining > rubber > forest > logging > urban areas > agriculture > oil palm. These findings show that the ANNs are highly reliable means of relating water quality to land use, thus integrating land use development with river water quality management.
This paper reviews the related literature reported in 2019 about various types of wastewaters associated with chemical and allied products. The subjects comprise wastewaters produced from various activities in agricultural, chemical, dye, petrochemical, and pharmaceutical. PRACTITIONER POINTS: Bioflocculant chitosan was used for sludge dewatering and the treatment of water and wastewater, and polishing of sanitary landfill leachate. Alkaline lignin-based flocculants were used to achieve excellent color removal for paper mill sludge. Powdered activated coke was used to remove COD (chemical oxygen demand) from chemical industry wastewater effluents.
The high-strength leachate produced from sanitary landfill is a serious issue around the world as it poses adverse effects on aquatic life and human health. Physio-chemical technology is one of the promising options as the leachate normally presents in stabilized form and not fully amendable by biological treatment. In this research, the effectiveness of natural zeolite (clinoptilolite) augmented electrocoagulation process (hybrid system) for removing high-strength ammonia (3,442 mg/L) and color (8,427 Pt-Co) from naturally saline (15 ppt) local landfill leachate was investigated. A batch mode laboratory-scale reactor with parallel-monopolar aluminum electrodes attached to a direct current (DC) electric power was used as an electrocoagulation reactor for performance enhancement purpose. Optimum operational conditions of 146 g/L zeolite dosage, 600 A/m2 current density, 60 min treatment time, 200 rpm stirring speed, 35 min settling duration, and pH 9 were recorded with up to 70% and 88% removals of ammonia and color, respectively. The estimated overall operational cost was 26.22 $/m3 . The biodegradability of the leachate had improved from 0.05 to 0.27 in all post-treatment processes. The findings revealed the ability of the hybrid process as a viable option in eliminating concentrated ammonia and color in natural saline landfill leachate. PRACTITIONER POINTS: Clinoptilolite was augmented on the electrocoagulation process in saline and stabilized landfill leachate (15 ppt). The high strength NH3 -N (3,442 mg/L) and color (8,427 Pt-Co) were 70% and 88% removed, respectively. The optimum conditions occurred at 140 g/L zeolite, 60 mA/cm2 current density, 60 min, and final pH of 8.20. The biodegradability of the leachate improved from 0.05 to 0.27 after the treatment. This hybrid treatment was simple, faster, and did not require auxiliary electrolyte.
Landfill leachate is well known as a hazardous byproduct from dumpling sites that has a negative impact on the environment and human life. Therefore, an effective treatment is imperative to overcome this issue. This research study investigates the effectiveness of zirconium tetrachloride (ZrCl4 ) and tin tetrachloride (SnCl4 ) as a coagulant in leachate treatment. Two parameters selected as a performance indicator in this study are color and chemical oxygen demand (COD). The data obtained showed that SnCl4 performed well as a coagulant with removal percentages of color and COD, which are 97% and 77%, respectively. Furthermore, the potential of integrated treatment using ozonation (O3 ) and the coagulation-flocculation process was also investigated. Four sequences of integrated treatment setup for this study were ozonation followed by jar test (ZrCl4 as a coagulant), ozonation followed by jar test (SnCl4 as a coagulant), jar test (ZrCl4 as a coagulant) followed by the ozonation process, and jar test (SnCl4 as a coagulant) followed by the ozonation process. The experimental data showed that the combination treatment of SnCl4 as a coagulant (jar test) followed by the ozonation process had recorded the highest removal of color (97.1%) and COD (88%) compared to other sequences. Moreover, the biodegradability ratio of this sequence also improved from 0.03 to 0.28, compared with other methods. Comparatively, integrated treatment is more effective in treating stabilized landfill leachate compared to the coagulation flocculation process alone. PRACTITIONER POINTS: Stabilized landfill leachate is difficult to be treated by natural coagulants or biological process. SnCl4 performed well as a coagulant in removing COD and colour from landfill leachate compared to ZrCl4 . However, too much usage of SnCl4 potentially generate secondary pollutant. Therefore, combination with O3 as pre-treatment is investigated. Combination treatment of SnCl4 ( as coagulant) with O3 had recorded the highest removal of colour (97.1%) and COD (88%). The biodegradability ratio of this sequence also improved from 0.03 to 0.28.
Microbial fuel cells (MFCs) represent an emerging technology that focuses on power generation and effluent treatment. This review compiles articles related to MFCs using azo dye as the substrate. The significance of the general components in MFCs and systems of MFCs treating azo dye is depicted in this review. In addition, degradation of azo dyes such as Congo red, methyl orange, active brilliant red X-3B, amaranth, reactive blue 221, and acid orange 7 in MFCs are summarized. Further exploration and operational modification are suggested to address the challenges of complete removal of azo dye with maximum power generation in an MFC. In addition, a sequential treatment system with MFCs is suggested for complete mineralization of azo dye.
The effect of physical shearing on the attachment of six Pseudomonas aeruginosa strains and six Burkholderia cepacia strains to glass, stainless steel, polystyrene and Teflon® was determined. A significant (p < 0.05) decrease in hydrophobicity was apparent for all P. aeruginosa strains (17-36%) and B. cepacia, MS 5 (20%) after shearing. A significant (p < 0.05) decrease in attachment of some P. aeruginosa (0.2-0.5 log CFU/cm2) and B. cepacia (0.2-0.4 log CFU/cm2) strains to some surface types was apparent after shearing. Significant (p < 0.05) correlation was observed for both numbers of flagellated cells and hydrophobicity against attachment to glass, stainless steel and polystyrene for P. aeruginosa while only hydrophobicity showed significant correlation against the same surfaces for B. cepacia. Scanning electron microscopy and protein analysis showed that shearing removed surface proteins from the cells and may have led to the observed changes in hydrophobicity and attachment to abiotic surfaces.
Membrane distillation (MD) frequently deals with membrane biofouling caused by deposition of algal organic matter (AOM) from algal blooms, hampering the treatment efficiency. In this study, AOMs, which are soluble extracellular polymeric substance (sEPS), bounded EPS (bEPS), and internal organic matter (IOM) from three benthic species (Amphora coffeaeformis, Cylindrotheca fusiformis, and Navicula incerta) were exposed to a temperature range to resemble the MD process. Results showed that EPS had higher polysaccharide fraction than protein with 85.71%, 68.26%, and 71.91% for A. coffeaeformis, N. incerta, and C. fusiformis, respectively. Both the EPS polysaccharide and protein concentration linearly increase with temperature, but the opposite was true for IOM and high-molecular-weight (HMW) polysaccharide. At 80°C, 5812.94 μg/g out of 6304.28 μg/g polysaccharide in A. coffeaeformis was of low molecular weight (LMW); hence, these findings suggested that they were the major foulants to clog the narrow pores within virgin hydrophobic membrane, forming a conditioning layer followed by deposition of HMW and hydrophilic polysaccharides onto the macropores to cause irreversible fouling. Cell lysis occurring at higher temperature increases the total protein content about 25% within the EPS matrix, inducing membrane plugging via hydrophobic-hydrophobic interactions. Overall, the AOM composition at different temperatures will likely dictate the fouling severity in MD. PRACTITIONER POINTS: EPS production of three benthic diatoms was the highest at 80°C. EPS from diatoms consists of at least 75.29% of polysaccharides. Small molecular weight carbohydrates (<12 kDa) were potential foulants. Proteins of internal organic matter (>56%) give irreversible attachment towards membranes. A. coffeaeformis was considered as the most fouling diatoms with highest EPS amount of 6304.28 μg/g.
Biogranulation is an effective biological technology suitable for the treatment of various wastewaters. However, the major drawback of this technique is the long start-up period for biogranule development. Hence, the primary focus of this study was on cell surface hydrophobicity which is the main parameter that indicates cell agglomeration during the initial self-immobilization process of aerobic granulation. The effects of sludge concentration and magnetic activated carbon on cell surface hydrophobicity were investigated in this study. Response surface methodology (RSM) was applied to design, analyze, and optimize the outcome of the study. Experiments were performed at sludge concentration of 1,000-3,000 mg/L and magnetic activated carbon mass of 1-5 g/L with 24 hr of aeration time. The results show that both variables yielded a positive significant effect on the initial development of aerobic granulation with 56% surface hydrophobicity. Interaction effects between variables on the responses were significant with positive estimated interaction effect at all different measured aeration time. The magnetic activated carbon acted as nuclei to induce bacterial attachment and further enhanced the initial process of biogranule development under optimal condition of 1:1.1 (sludge concentration: magnetic activated carbon). PRACTITIONER POINTS: Cell surface hydrophobicity was evaluated Magnetic activated carbon enhanced cell surface hydrophobicity Response surface methodology was employed for analyses Magnetic activate carbon mass and biomass concentration was significant Magnetic activated carbon acted as nuclei to improve biogranulation.
Landfill leachate can threaten the environment and human life. Therefore, this study aims to investigate the efficiency of ozone (O3 ), O3 with zirconium tetrachloride (O3 /ZrCl4 ), and O3 with tin tetrachloride (O3 /SnCl4 ) in remediating the stabilized anaerobic landfill leachate (SAL) from Alor Pongsu, Perak. Hydroxyl radical (OH•) is an important oxidizing agent in the ozonation process. Its presence was tested using tert-butyl alcohol. Results showed that using ZrCl4 and SnCl4 in ozonation boosted the generation of hydroxyl radical, thereby enhancing the oxidation process and pollutant removal inside the sample. The O3 /ZrCl4 mix at chemical oxygen demand (COD) to ZrCl4 ratio of 1:1.5, pH 8-9, and 90-min reaction time resulted in the highest reduction rates of COD and color at 91.9% and 99.6%, respectively. All results demonstrated that the optimum performance occurred at alkaline conditions (pH > 8), proving that OH radicals primarily oxidized the pollutants through an indirect reaction pathway. The biodegradability (biochemical oxygen demand/COD) ratio was also considerably improved from 0.02 (raw) to 0.37 using O3 /ZrCl4 , compared with using O3 alone and using O3 /SnCl4 , which only recorded 0.23 and 0.28, respectively, after the treatment. The study demonstrated that O3 /ZrCl4 was the most efficient combination. PRACTITIONER POINTS: The O3 /ZrCl4 recorded the highest COD and color removals. The O3 /ZrCl4 combination also recorded higher OH• concentrations. The biodegradability of leachate (BOD5 /COD ratio) improved from 0.02 to 0.37.
Hexavalent chromium, emanating primarily from the electroplating industries, can be reduced to the less toxic trivalent variety by several methods, including emulsion liquid membrane (ELM). In this work, studies on the continuous removal of chromium from authentic electroplating wastewater by ELM are reported. The effects of treat ratio, external feed phase, and stripping agent concentration were examined. A mathematical boundary breakage model was used to study the extraction efficiency of chromium through the ELM process. The model representing the prediction of ELM extraction performance for chromium was validated through the comparison between the simulation and experimental results. The result showed the simulation model is found to be in good agreement with the experimental result. Almost 100% of 40 ppm chromium in the external feed phase was extracted within 3 to 5 min using 0.022 M TOMAC as extractant, 1.0 M acidic thiourea in the internal phase, and 1 to 5 of treat ratio. PRACTITIONER POINTS: Hexavalent chromium, emanating primarily from electroplating industries, can be reduced to the less toxic trivalent using ELM process. The developed method was tested for its applicability with predominant species of Cr2 O7 2- in real rinse electroplating wastewater. The extraction efficiency (%) of Cr (VI) was almost 100% for 40 ppm Cr in the external feed phase within 3 to 5 min. The result showed the simulation model is found to be in good agreement with the experimental result.
The combination of UV and water-soluble Fe(III) complexes is an effective method for generating Fe(II) in situ for activating advanced oxidation processes. This study explored the potential of Fe(III)-diethylenetriaminepentaacetic acid (Fe(III)-DTPA) and Fe(III)-ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (Fe(III)-EGTA) in activating the UV/persulfate (UV/PS) for sulfamethazine removal. The initial screening showed that Fe(III)-EGTA and Fe(III)-DTPA could significantly improve the rate of sulfamethazine removal. The optimum molar ratios of persulfate to Fe(III)-DTPA and Fe(III)-EGTA were 100:1 and 100:2.5. The predicted percentage of sulfamethazine removal under the optimized conditions, obtained using response surface methodology, was ~99% for both catalysts. The pH range of 6 to 8 did not significantly affect the performance of UV/PS in the removal of sulfamethazine. The percentage sulfamethazine removal in the selected water samples was ranged from 93.6% to 99.6%, agreeing with the predicted value. The performance of both catalysts in activating UV/PS is comparable with that of the frequently used Fe(III)-EDDS. PRACTITIONERS POINTS: The potential of Fe(III)-DTPA and Fe(III)-EGTA in activating UV/persulfate (UV/PS) was explored. Fe(III)-DTPA and Fe(III)-EGTA improved the performance of UV/PS in sulfamethazine removal. Fe(III)-DTPA and Fe(III)-EGTA are effective in catalyzing UV/PS under pH 6 to 8. The performance of Fe(III)-DTPA and Fe(III)-EGTA is comparable with well-studied Fe(III)-EDDS.
Hazardous industrial wastes negatively impact the environment by creating issues for aquatic as well as human's life. This study investigates the treatment of hazardous industrial wastewater using cost-effective graphite adsorbent along with electrochemical regeneration integrated with renewable solar energy. The synthetic industrial effluent containing crystal violet dye was treated using an adsorbent (Nyex™ 1000) having a surface area of 1.0 m2 g-1 . The efficiency of removing solute was found to be more than 90%. The adsorbent regeneration efficiency was achieved at 99.5% by passing a charge of 100 C g-1 at current density of 10 mA cm-2 for 1 h. Solar energy was integrated with electrochemical reactor for the regeneration of adsorbent to make the system cost-effective and self-sustainable. PRACTITIONER POINTS: Industrial hazardous wastewater treatment with a cost-effective graphite integrated adsorbent. Development of renewable solar energy-integrated with electrochemical system for regeneration. Regeneration efficiency of adsorbent Nyex™ 1000 was achieved around 99.5% with integrated system. Sustainable system was introduced to incorporate with renewable energy for waste water treatment.
In this current work, the performance of an aerobic granular sludge (AGS) for real textile wastewater was investigated based on system operational parameters evaluation. The study was performed for 90 days, and sampling was done once a week in which textile dyeing effluent from the textile mill was collected and subjected to laboratory-scale treatment. The samples from the inlet, the outlet of the wastewater plant, and within the bioreactor were collected at various concentrations of MLSS, and hydraulic retention remained the same in the investigated period of 53 hours. The objective of this study was to analyze the AGS system performance assessment by evaluating the effect of different MLSS concentrations on chemical oxygen demand (COD), TSS, and oil/grease removal from real-based textile water. The results showed that removal of organic material from the process water increases with an increase in MLSS concentration in the bioreactor and gradually shifts removal of COD from 91.2% to 94.5%. As the concentration of microorganisms in the reactor (aeration tank) increases, the degradation of waste organics in the wastewater increases as well. Moreover, the % removal of total suspended solids (83.5 to 98 %) and removal of oil/grease (62.5 to 76.4%) were also increased. These results ultimately suggest that the utilization of an activated sludge system can effectively treat complex and highly polluted denim textile wastewater to avoid secondary pollution posed by this industry.
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.
A circular gravity-phase separator using coalescing medium with cross flow was developed to remove oil and suspended solids from wastewaters. Coalescence medium in the form of inclined plates promotes rising of oil droplets through coalescence and settling of solid particles through coagulation. It exhibits 22.67% higher removal of total suspended solids (TSS) compared to separators without coalescing medium. Moreover, it removed more than 70% of oil compared to conventional American Petroleum Institute separators, which exhibit an average of 33% oil removal. The flowrate required to attain an effluent oil concentration of 10 mg/L (Q(o10)) at different influent oil concentrations (C(io)) can be represented by Q(o10) x 10(-5) = -0.0012C(io) + 0.352. The flowrate required to attain an effluent TSS concentration of 50 mg/L (Q(ss50)) at different influent TSS concentrations (C(iss)) can be represented by Q(ss50) x 10(-5) = 1.0 x 10(6) C(iss)(-2.9576). The smallest removable solid particle size was 4.87 microm.
Malaysia encounters a consistent rise in the generation of solid waste and leachate on a daily basis. It should also be noted that leachate has a low degree of biodegradability (BOD5 /chemical oxygen demand [COD]), as shown by its BOD5 /COD ratio. Its high toxicity levels significantly threaten the environment, water bodies, and human well-being. High concentrations of COD, color, and ammoniacal nitrogen (NH3 -N) in leachate prevent this wastewater from being allowed to be discharged directly into the water body. Therefore, an effective process to remove the pollutant is desired. The aims of this study are to investigate the performance of ozonation with two metallic compounds, ZrCl4 and SnCl4 , and optimize their performance using response surface methodology (RSM). In this study, the performance of ozonation with ZrCl4 (O3 /ZrCl4 ) recorded better pollutant removals compared with the ozonation with tin tetrachloride (O3 /SnCl4 ), as seen in the removals of 99.8%, 93.5%, and 46.3% for color, COD, and NH3 -N, respectively. These removals were achieved by following the experimental model (optimum experiment condition) generated by RSM at O3 dosage of 31 g/m3 , COD and ZrCl4 dosage ratio (COD, mg/L/ZrCl4 , mg/L) of 1:1.35, with the pH solution of 8.78 and reaction time of 89 min. The R2 of each parameter for this model was recorded as 0.999 (COD), 0.999 (color), and 0.998 (NH3 -N), respectively. These data indicated that the model is well fitted as the predicted data by statistical calculation and in good agreement with the actual data. PRACTITIONER POINTS: The performance of O3 /ZrCl4 and O3 /SnCl4 was examined for remediate stabilized landfill leachate. The performance of O3 /ZrCl4 and O3 /SnCl4 was optimized using RSM, and a set of experimental models was generated and tested. O3 /ZrCl4 recorded the higher removal of COD, color, and NH3 -N compared with O3 /SnCl4 . At best condition, both methods recorded removal as 89% to 99.8% of pollutants in leachate and product clear effluent. This finding gives a new approach to treat landfill leachate effectively and efficiently.
This study was conducted to evaluate the effect of the toxicity levels of the coagulation and flocculation process on raw and treated leachate using acute toxicity tests. Tin tetrachloride (SnCl4 ) and the Jatropha curcas (JC) seed were used as coagulant and coagulant aid to remove concentrated suspended solids, SS (534 mg/L), color (19,297 Pt-Co), and chemical oxygen demand (COD) (4188 mg/L) in a stabilized landfill leachate. The toxicity effects on local red tilapia fish (Oreochromis niloticus) were investigated, which involved three main steps, namely, acclimatization, range-finding test, and short-term definitive test. The presence of JC seed (0.9 g/L) as a flocculant reduced the dosage of SnCl4 from 11.1 to 8.5 g/L and exhibited good removals of 99.78%, 98.53%, and 74.29%, respectively, for SS, color, and COD. The toxicity test indicated that only five fish died in the first 12 h for the treated sample compared with seven deaths for untreated leachate. In 96 h, a total of 42 and 31 mortality rates were noted for the raw and treated leachate samples, respectively. The treated sample could reduce the toxicity effects to the tested tilapia fish and is safe to be discharged at appropriate dilution concentrations. PRACTITIONER POINTS: Coagulation-flocculation by Tin (IV) chloride and Jatropha Curcas (JC) was investigated. Almost complete reduction of SS was obtained at 8.5 g/L of SnCl4 and 0.9 g/L of JC as flocculant. The toxicity effect was evaluated using red tilapia (Oreochromis niloticus) fish as the indicator. Treated leachate was considered acceptable as the number of dead fish was lower than the untreated leachate.