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The development of novel materials is critical for the sustainable improvement of adsorption of organic dye contaminants. Metal-organic frameworks (MOFs) have recently gained a lot of attention due to their unique features. One of the most representative MOFs is MOF-5 [Zn4O(BDC) 3]. This study compiles the recent research on the adsorptive removal of different organic dyes from aqueous solutions using pristine and modified MOF-5. The history and background of MOFs together with synthesis methods and characterization were briefly discussed. The development of MOF-5-based materials and their effectiveness under various process parameters in organic dyes adsorption were briefly highlighted. The discussion related to the characterizations of MOF-5 was also included. This review also outlined several challenges that the scientific community should investigate further to improve MOF-5 applications in organic dye adsorption. This review provides a valuable resource for researchers intending to use MOF-5 to remove organic dye from aqueous solutions.

Graphene is a promising candidate for use as a cushioning/filler material in composites due to its extraordinary mechanical and thermal properties. When added to composite materials, graphene can improve the composite's overall strength, durability, and impact resistance. One of the primary benefits of using graphene as a cushioning/filler material in composite materials is its high strength-to-weight ratio. Graphene is one of the most robust materials known to man, and when added to composite materials, it can significantly increase their strength without adding much weight. Another benefit is its high thermal conductivity. Graphene can dissipate heat quickly and efficiently, which can be advantageous in applications where thermal management is critical, such as electronics and aerospace. The addition of graphene can reduce the amount of energy transferred during impact, reducing the risk of damage or failure of the composite material. In addition to its thermal and mechanical properties, graphene is highly chemically resistant, making it ideal for use in harsh environments. It is also relatively inexpensive compared to other high-performance materials, making it an attractive option for large-scale industrial applications. Overall, graphene has the potential to revolutionize the use of composite materials by providing a high-strength, lightweight, and thermally conductive cushioning/filler material that can improve the durability and performance of composite materials in a diverse range of applications. Various application in diverse field has been elaborated in this review work.

Palm oil wastewater treatment was investigated via a filtration process using raw and calcinated limestone. Column studies were conducted using different limestone sizes (4, 12, and 20 mm), calcination temperature (800 °C and 600 °C) and various filtration rates (20, 60, and 100 mL/min), and a comparison was made with raw limestone under similar conditions. The response surface methodology using central composite design was employed to optimize the process parameter. The experimental data was analyzed via the analysis of variance to identify the interaction between the parameters and the dependent parameter. The results showed that the colour removal increased with an increase in temperature (800 °C) for filtration rate of 20 mL/min, the retention time of 317 min and the smaller size (4 mm) of limestone, and decreased with an increase in the filtration rate and size of raw limestone. Based on the achieved results, the optimum condition for colour removal was at temperature 800 °C (61%), 600 °C (56%) and raw limestone (49%), respectively, with the same experimental setup (flow rate of 20 mL/min and limestone size of 4 mm). According to the statistical analysis, quadratic models demonstrated significant values (0.000) for the response (colour). Freundlich and Langmuir isotherms also provided good correlation coefficient for colour removal. The data conforms to the Langmuir isotherm with the best fit model (R2= 0.7).

This paper investigates the potential use of anthracite coal to remove Fe, Mn, UV254, and colour from pre-ozonated groundwater using batch experiment studies. Pre-ozonated groundwater samples were prepared in a laboratory to present the actual characteristics of groundwater samples. General characteristics for anthracite, as well as for groundwater samples, were examined. The influences of anthracite dosage, pH, agitation speed, and contact time on the reduction of tested parameters were discussed. Also, three adsorption isotherms (Langmuir, Freundlich, and Temkin), as well as kinetics models, were evaluated. Results demonstrated that the maximum removal of Fe (67%) occurred at 100 g of anthracite dosage, and no significant removal of Mn was observed. In addition, anthracite was capable of removing UV254and colour using a dosage of 100 g. However, the maximum removal efficiency of colour was 76% using the same anthracite dosage of 100 g. The optimum shaking speed of 300 rpm resulted in the maximum removal efficiency of all parameters. The optimum pH was 7, which resulted in the maximum removal efficiency of Fe (40%), Mn (7%), UV254(43%), and colour (50%). The optimum contact time was 90 min for all parameters with a dosage of 100 g which resulted in the removal efficiency of 54%, 52%, and 70% for Fe, Mn, UV254, and colour. The adsorption and kinetics models were well fitted with the experimental results. Overall, this study demonstrated that anthracite could be a good practical option for groundwater treatment.

A combined process of acrylic biomass carrier and activated sludge system (traditional system) was accomplished to treat sanitary landfill young leachate with a high concentration of ammoniacal nitrogen and organic material. Stable treatment performance of an acrylic biomass carrier reactor with activated sludge traditional reactor combined with bio-fringe loaded with microorganisms (CASBF) compared to activated sludge traditional reactor (CASR) was obtained under 10 L laboratory-scale reactor as 24 h sequencing batch reactor system and 2–5 mg/L dissolved oxygen, the temperature of (20°C–25°C), pH 7 ± 1, a volumetric organic load of 1,968 mg/L COD (chemical oxygen demand – COD), high ammoniacal nitrogen loading rates of 1,904.1 mg/L, food to microorganism ratio of 0.25, mixed liquor volatile suspended solid of 1,500 mg/L, sludge age of 2.7 d and hydraulic retention time of 1.7 d for 13 d duration of the experiment, respectively. The efficiency of both reactors was assessed based on the reduction in biochemical oxygen demand (BOD5), COD, ammoniacal nitrogen (NH3–N), total Kjeldahl nitrogen (TKN), phosphate (PO43–), nitrite (NO2–1), nitrate (NO3–1), suspended solids and color. The results revealed that the reactor with CASBF efficiency removed NO2–1, NO3–1and PO43–were 77.7% with effluent concentration 10 mg L–1, 86.25% with effluent concentration 21.0 mg L–1, and 63.2% with effluent concentration 18.1 mg L–1respectively from young leachate in comparison to CASR which exhibited the efficiently removed of NO2–1, NO3–1, and PO43–was 20.7% with effluent concentration 36.1 mg L–1, 54.2% with effluent concentration 69.9 mg L–1, and 45.6% with effluent concentration 26.5 mg L–1, respectively. However, the reduction of NH3–N also TKN was more within the CASR and achieved 68.7% with effluent concentration 538.90 mg L–1for TKN and 92.5% with effluent concentration 134.2 mg L–1for NH3–N. This reduction is achieved via nitrification and denitrification processes. These findings indicated that CASBF has high efficiency of removal of COD, BOD, NO3–1, and PO43–from sanitary landfill young leachate and have the applicability for sanitary landfill young leachate treatment.

Landfills are the main option for waste disposal all over the world. Most of the landfill sites across the world are old and are not engineered well to prevent contamination of the underlying soil and groundwater by the toxic leachate. The present study examines the potential use of raw zeolite and heated activated zeolite in the reduction of COD, NH3-N, and colour from leachate. Zeolite was activated using different temperatures at 150 °C, 200 °C, and 250 °C for 3 h. General characterization was conducted for raw zeolite and heat-activated zeolite to investigate the influence of temperature on zeolite properties. Batch experiments were conducted at the optimum dosage of zeolite and pH. Results demonstrated that the optimum dosage of raw zeolite was 10 g with 53.1%, 22.5% and 46% reduction of NH3-N, COD, and colour, respectively. The optimum pH for NH3-N was 7 with a percentage removal of 55.8% while better reduction of COD and colour was obtained at pH 4 with a percentage removal of 24.3% and 73.8%, respectively. Also, the optimum temperature tested was at 150 °C, where the optimum dosage using activated zeolite heated at 150 °C was 10 g, resulted in the maximum reduction of NH3-N, COD, and colour of 45.1%, 11.8% and 43.7%, respectively. The optimum dosage of activated zeolite heated at 200 °C and 250 °C, which was 25 g. This indicates that the use of the activated zeolite heated at 150 °C can achieve the optimum removal at a lower cost which is applicable for a larger scale of wastewater treatment. In addition, it was found that the capacity of the zeolite before and after heat activation was 41.30 cmol/kg and 181.90 cmol/kg, respectively. The adsorption isotherm analysis reveals that both Freundlich and Langmuir isotherms were in agreement with experimental data. However, the Freundlich isotherm model was more favourable than Langmuir isotherm to evaluate the adsorption equilibrium of the three pollutants as verified by the high R2values.

This paper aims to present the characteristic of dewatered sewage sludge (SS) and red gypsum (RG) to determine their recycling potentials into a valuable product. The materials were characterized based on their physical-mechanical-chemical properties and morphology. The results showed that dewatered sewage sludge and red gypsum could complement each other when used together to form a new material the merits of which will be investigated in subsequent studies. RG has a better performance in term of plasticity and strength than SS due to fines content in the former and therefore its ability to retain moisture that contributes to cohesion between particles. Fine prisms and closer packing particles add strength in RG leading to higher resistance in compression. Unlike RG, SS has coarser particle and more voids causing it to lose the moisture content and becomes easily disintegrated. Chemical compositions of RG and SS as determined by XRF demonstrated a significant amount of CaO in the former and SiO2 in the latter; the formation of hydrated products in the form of CSH and CAH gel from hydration or pozzolanic reaction contributes to strength improvement of the SS.

Coagulation-flocculation has been extensively used as a semi-aerobic landfill leachate treatment, prior to other treatment methods. Polyaluminium chloride (PAC) coagulants is prominent in landfill leachate treatment, however the application of PAC may introduce potentially harmful residuals into the aquatic environment. In this study, crosslinked starch-based coagulants had been produced from oil palm trunk waste (C-OPTS). To date, no attempt has been made to avail crosslinked oil palm trunk starch application in landfill leachate treatment. Based on the results, C-OPTS can be employed as coagulants. Jar test results had ascertained that optimum pH and dosages value for C-OPTS and PAC. Indeed, no pH adjustment was required for C-OPTS and its optimum dosage was only one-eighth of PAC optimum dosage. Therefore, C-OPTS would be an alternative coagulant substituting PAC, depending on leachate condition. The overall findings concluded that C-OPTS were feasible for landfill leachate treatment in terms of coagulation performance and sustainable environmental management.

The main issue in landfilling in developing countries is the management of leachate. Leachate is rich in organic compounds, ammonia, heavy metals, and other hazardous chemicals. COD, colour, and NH3-N, are among the problematic parameters that are difficult to be completely removed. The treatments depend on leachate characteristics, operation and capital costs, and regulations. The development of holistic solutions to leachate-related problems has been widely promoted. Multiple-stage treatments in the form of physical, biological, chemical, and combination methods are always necessary. This paper discusses issues on landfill technology and recent techniques for the treatment of the leachate. The low biodegradability and high COD, colour, and NH3-N content of leachate treatment peculiar to semi-aerobic landfills in developing countries, especially in Malaysia, is described. Some of the challenging issues in overall leachate treatment processes are also elucidated.

The current study aimed to assess the performance of utilise Zirconium reagent during ozonation of anaerobic stabilised leachate. In this study, quadratic models using response surface methodology software was utilised to design the experiments and evaluate the interaction between experimental factors, such as zirconium tetrachloride, pH, and reaction time, at constant ozone dosage (27 g/m3). The performance of the new ozonation method was evaluated in terms of the removal of the chemical oxygen demand (COD), NH3-N and colour. The obtained quadratic models for colour, NH3-N and COD removal was considered significant (P < 0.0001). The optimal removal for of 100%, 90%, and 66% for colour, COD and NH3-N, was obtained at 38 min reaction time, ZrCl4dosage (1/2(COD/ZrCl4g/g) and pH 4.5, using 27g/m3ozone dosage, respectively. The results obtained in this study were compared with zirconium only and ozone only, to evaluate its effectiveness. The performance of the new oxidation method(O3/ZrCl4) better than other related methods for the removal of colour, COD and NH3-N.

A coagulation and flocculation treatment method was applied on partially stabilised leachate of Matang landfill. The interactions and effects of dose and pH on the removal of suspended solid (SS), colour and chemical oxygen demand (COD) were investigated, analysed and optimised through RSM. The optimal condition obtained from the satisfactory mathematical model was 0.24 g/L Fe and 4.94 of poly iron chloride (PHI) dose and pH, respectively. Confirmatory experiment indicates good agreement between model prediction and experimental value. Therefore, RSM is an appropriate statistical tool in the optimisation of PHI coagulation and flocculation process.

AbstractIn this study, three start-up techniques of modified anaerobic inclining-baffled reactor (MAI-BR) were performance to understand the effect of inoculum source and effluent recycle on the treatment of recycled paper mill effluent (RPME). Flocculant anaerobic sludge from a palm oil mill pond and digested anaerobic sludge from a sewage treatment plant were inoculated in the first and second start-up/phase1, respectively. Results show that high chemical oxygen demand (COD) removals of 93 and 88% were achieved in the first and second start-up/phase1, respectively. The amount of methane produced in the second start-up/phase1 within 15 d was doubled as compared to the amount produced in the first start-up, with a higher methane content of 79% (as compared to 62% in the first start-up). This result indicated that the inoculum source has a significant effect on the reactor performance. The results in the second start-up/phase2 also showed that COD removal and methane production increased up to 94% and 0.52 L CH4/d, respectively. This finding can conclude that the use of effluent recycle has a favorable effect on the performance of MAI-BR. During the first start-up, second start-up/phase1, and second start-up/phase2, the volatile fatty acid/alkalinity compartmental ratios were varied at 0.01–0.06, 0.03–0.43, and 0.02–0.14, respectively, and the overall effluent pH levels were higher than 6.5. The findings indicate the stability of the MAI-BR system in treating RPME.

In this study, three start-up techniques of modified anaerobic inclining-baffled reactor (MAI-BR) were performance to understand the effect of inoculum source and effluent recycle on the treatment of recycled paper mill effluent (RPME). Flocculant anaerobic sludge from a palm oil mill pond and digested anaerobic sludge from a sewage treatment plant were inoculated in the first and second start-up/phase1, respectively. Results show that high chemical oxygen demand (COD) removals of 93 and 88% were achieved in the first and second start-up/phase1, respectively. The amount of methane produced in the second start-up/phase1 within 15 d was doubled as compared to the amount produced in the first start-up, with a higher methane content of 79% (as compared to 62% in the first start-up). This result indicated that the inoculum source has a significant effect on the reactor performance. The results in the second start-up/phase2 also showed that COD removal and methane production increased up to 94% and 0.52 L CH4/d, respectively. This finding can conclude that the use of effluent recycle has a favorable effect on the performance of MAI-BR. During the first start-up, second start-up/phase1, and second start-up/phase2, the volatile fatty acid/alkalinity compartmental ratios were varied at 0.01–0.06, 0.03–0.43, and 0.02–0.14, respectively, and the overall effluent pH levels were higher than 6.5. The findings indicate the stability of the MAI-BR system in treating RPME.

AbstractAs textile wastewater is a major source of surface water pollutants when not sufficiently treated prior to discharge, strict disposal regulations were set and monitored by environmental authorities. As such, continuous research is necessary in textile wastewater remediation. In this study, real textile wastewater samples were directly collected from the wastewater discharge point of a manufacturer in Prai, Malaysia. Various particle sizes of clinoptilolite were applied to treat the wastewater in a series of batch experiments at a predetermined dosage, pH, and contact time. Removal of three main parameters [i.e. color, suspended solids (SS), and chemical oxygen demand (COD)] was monitored. The removal rates of color, SS, and COD were 47.9, 48, and 37.4%, respectively, at particle sizes larger than 2 mm and then increased to 91, 96, and 62%, respectively, at particle sizes of 75–250 μm. The highest COD removal of 70% was also achieved at particle sizes smaller than 75 μm. These findings indicate that 75–250 μm is the optimal size range of clinoptilolite for simultaneous removal of the three parameters under the same experimental conditions. After wastewater treatment, the residual concentration of SS was 10 mg/L, which is within the standard limit of 50 mg/L effluent discharge.

As textile wastewater is a major source of surface water pollutants when not sufficiently treated prior to discharge, strict disposal regulations were set and monitored by environmental authorities. As such, continuous research is necessary in textile wastewater remediation. In this study, real textile wastewater samples were directly collected from the wastewater discharge point of a manufacturer in Prai, Malaysia. Various particle sizes of clinoptilolite were applied to treat the wastewater in a series of batch experiments at a predetermined dosage, pH, and contact time. Removal of three main parameters [i.e. color, suspended solids (SS), and chemical oxygen demand (COD)] was monitored. The removal rates of color, SS, and COD were 47.9, 48, and 37.4%, respectively, at particle sizes larger than 2 mm and then increased to 91, 96, and 62%, respectively, at particle sizes of 75–250 μm. The highest COD removal of 70% was also achieved at particle sizes smaller than 75 μm. These findings indicate that 75–250μm is the optimal size range of clinoptilolite for simultaneous removal of the three parameters under the same experimental conditions. After wastewater treatment, the residual concentration of SS was 10 mg/L, which is within the standard limit of 50 mg/L effluent discharge.

AbstractThree start-up techniques were investigated to evaluate the suitability of the bench-scale modified anaerobic inclining-baffled reactor (MAI-BR) for the treatment of recycled paper mill effluent (RPME) and to achieve an improved understanding of the inoculum to substrate ratio (ISR). The ISR ratios used were 3.53, 1.17, and 10.63 g volatile suspended solids (VSS)/g chemical oxygen demand (COD) for the first, second, and third start-ups, respectively. On a 30-d duration, the first start-up succeeded in removing 72% of the COD with an effluent pH of 6.2 and a methane production of 0.076 L/d. The second start-up was considered unfavorable after 16 d because of low methane production and effluent pH level. The third start-up with a 21-d duration was the best because of its 87% COD removal, 6.82 effluent pH, and 0.164 L/d methane production. The effluent volatile fatty acid (VFA)/alkalinity ratios were concurrently varied as 0.56, 0.45, and 0.034 for the first, second, and third start-ups, respectively. Subsequently, the VSS/TSS ratio of 0.78–0.86 formed in the reactor was sufficient to control biomass washout. The third start-up demonstrated that an ISR of more than 10 g VSS/g COD is an important factor that leads to a successful and efficient start-up operation. The batch feeding rate must be as low as 0.1 g COD/L d. Furthermore, the VFA/alkalinity ratio of the third start-up was excellent. The bench-scale unique design of the MAI-BR showed good performance in the RPME treatment within a period of less than one month.

Three start-up techniques were investigated to evaluate the suitability of the bench-scale modified anaerobic inclining-baffled reactor (MAI-BR) for the treatment of recycled paper mill effluent (RPME) and to achieve an improved understanding of the inoculum to substrate ratio (ISR). The ISR ratios used were 3.53, 1.17, and 10.63 g volatile suspended solids (VSS)/g chemical oxygen demand (COD) for the first, second, and third start-ups, respectively. On a 30-d duration, the first start-up succeeded in removing 72% of the COD with an effluent pH of 6.2 and a methane production of 0.076 L/d. The second start-up was considered unfavorable after 16 d because of low methane production and effluent pH level. The third start-up with a 21-d duration was the best because of its 87% COD removal, 6.82 effluent pH, and 0.164 L/d methane production. The effluent volatile fatty acid (VFA)/alkalinity ratios were concurrently varied as 0.56, 0.45, and 0.034 for the first, second, and third start-ups, respectively. Subsequently, the VSS/TSS ratio of 0.78–0.86 formed in the reactor was sufficient to control biomass washout. The third start-up demonstrated that an ISR of more than 10 g VSS/g COD is an important factor that leads to a successful and efficient start-up operation. The batch feeding rate must be as low as 0.1 g COD/L d. Furthermore, the VFA/alkalinity ratio of the third start-up was excellent. The bench-scale unique design of the MAI-BR showed good performance in the RPME treatment within a period of less than one month.

AbstractDifferent physical, chemical, and biological treatment methods are used to eliminate heavy metals and pollutants from wastewater and landfill leachate. Sequencing batch reactor (SBR) is a type of biological treatment. This study was conducted to study heavy metals elimination from urban wastewater and landfill leachate using an adsorbent, namely powdered ZELIAC (PZ) that improved SBR. PZ consists of portland cement, limestone, rice husk ash, activated carbon, and zeolite. Response surface methodology and central composite design were used to elucidate the nature of the response surface in the experimental plan and determine the optimum settings of the independent variables [aeration rate (L/min), contact time (h), and leachate to wastewater ratio (%; v/v)] and their reactions. To study the aerobic process, four dependent factors (Fe, Mn, Ni, and Cd) were evaluated as reactions. The results indicated that compared with SBR, PZ-SBR removed heavy metals more efficiently. At the optimum contact time (11.70 h), aeration rate (2.87 L/min), and leachate to wastewater ratio (20.13%) in PZ-SBR, removal efficiencies for Fe, Mn, Ni, and Cd were 79.57, 73.38, 79.29, and 76.96%, respectively.

Different physical, chemical, and biological treatment methods are used to eliminate heavy metals and pollutants from wastewater and landfill leachate. Sequencing batch reactor (SBR) is a type of biological treatment. This study was conducted to study heavy metals elimination from urban wastewater and landfill leachate using an adsorbent, namely powdered ZELIAC (PZ) that improved SBR. PZ consists of portland cement, limestone, rice husk ash, activated carbon, and zeolite. Response surface methodology and central composite design were used to elucidate the nature of the response surface in the experimental plan and determine the optimum settings of the independent variables [aeration rate (L/min), contact time (h), and leachate to wastewater ratio (%; v/v)] and their reactions. To study the aerobic process, four dependent factors (Fe, Mn, Ni, and Cd) were evaluated as reactions. The results indicated that compared with SBR, PZ-SBR removed heavy metals more efficiently. At the optimum contact time (11.70 h), aeration rate (2.87 L/min), and leachate to wastewater ratio (20.13%) in PZ-SBR, removal efficiencies for Fe, Mn, Ni, and Cd were 79.57, 73.38, 79.29, and 76.96%, respectively.

The risk of groundwater pollution due to municipal landfill leachate seepage has become a major environmental concern worldwide. Various types of physico-chemical treatment processes have been employed to achieve a satisfactory removal of refractory pollutants from the landfill leachate. Ozone has recently received much attention because of its highly powerful oxidation potential in landfill leachate treatment. The present study investigated ozonation process reaction, performance and limitation in landfill leachate treatment. Furthermore, the effectiveness of using a combination of various processes such as; coagulation-ozonation, Fenton-ozonation, adsorption-ozonation, and biological-ozonation) in leachate treatment are compared and evaluated. A literature survey indicated that an insufficient performance in term of pollutants removal efficiencies has been obtained when landfill leachate was treated via ozone alone. However, a combination of ozone and other processes achieved a considerable improvement in term of treatment efficiency; however, several stages and long treatment time are required.

Coagulation-flocculation is the most common chemical treatment method for wastewater treatment. Coagulant acts as neutralising agents for the electrical charges of particles in leachate. ZrCl4, which has never been applied for leachate treatment before, was tested in this research. Standard jar testing was conducted to determine the optimal pH and dosage in removing colour, suspended solids (SSs), ammonia, and organic content [ultraviolet absorbance at 254 nm wavelengths (UV254)] from semi-aerobic landfill leachate. The optimal ZrCl4dosage and pH were 1,500 mg/L and 4, respectively. These values corresponded to 93.4%, 94.3%, and 97% removals for SS, colour, and UV254, respectively. However, ammonia could not be removed by the coagulant, with only 2.2% of removal at pH 4 and 1,500 mg/L ZrCl4dosage.

In this research, a physico-chemical treatment method of coagulation-flocculation process is implemented in treating partially stabilized leachate from Matang Landfill, Perak, Malaysia. Central composite design has been used to optimize the independent variables namely polyaluminum chloride (PAC) coagulant dosage (A), rapid mixing speed (B) and rapid mixing time (C). The experimental results were analyzed by using analysis of variance (ANOVA). The results revealed that the percentage of color and COD removal was found increased by increasing rapid mixing speed with optimum removal of 95 % and 56 % respectively. Besides, the R-squared values implied that 86.22 % and 97.34% of the total variation explained by the model equation. Furthermore, the model analysis revealed that rapid mixing speed were significant for removal of color and COD through single parameter (B) and interaction between parameter (AB) respectively. This finding proves the influence of mixing parameter in coagulation-flocculation process for leachate treatment.

Coagulation and flocculation are two of the most common chemical treatment methods used in leachate treatment. Existing coagulants are mainly based on Al and Fe salts. The use of non-chemical based coagulants, especially natural polymers, in leachate treatment has not been thoroughly investigated. Natural coagulants have less harmful effects to human health compared with metal salts. This study aimed to investigate the effectiveness of ferric chloride (FeCl3) and chitosan as coagulant in removing the turbidity and color from landfill leachate. Leachate was collected from the Matang Landfill site located at Taiping, Perak, Malaysia. When used as the main coagulant in this study, FeCl3 was able to remove 97.78% of the turbidity and 95.54% of the color of the leachate at an optimum dosage of 3600 mg/L. At a dosage of 60 mg/L, chitosan only removed 23.52% of the turbidity and 14.67% of the color at pH levels of 9 and 4, respectively. The optimum pH value for FeCl3 was 6. Therefore, FeCl3 is an effective coagulant that can help to remove the colour and turbidity compared to chitosan.

AbstractLeachate is a liquid produced from the biodegradation of solid waste in landfill and is normally referred as highly polluted wastewater. Various treatment methods are available and it is highly depended on the characteristics of the leachate. One of the common and simplest methods is using coagulation process. The application of pre-hydrolyzed coagulants in coagulation process is well known for water and wastewater treatment. However, information on the application of pre-hydrolyzed coagulants, especially pre-hydrolyzed iron (PHI), in partially stabilized leachate treatments is not well documented. This study examined the application of PHI on the partially stabilized leachate by determining the optimum basicity ratio, pH, and dose through the removals percentage of suspended solid (SS), color, and chemical oxygen demand (COD). Laboratory jar tests revealed that the optimum PHI basicity ratio, pH, and dosage were 0.1, 5, and 0.2 g/L Fe, respectively. The optimum removals of SS, color, and COD were 99, 95, and 58% respectively. The results indicated that PHI could be potentially useful coagulant for removing SS, color, and COD from partially stabilized landfill leachate.

Leachate is a liquid produced from the biodegradation of solid waste in landfill and is normally referred as highly polluted wastewater. Various treatment methods are available and it is highly depended on the characteristics of the leachate. One of the common and simplest methods is using coagulation process. The application of pre-hydrolyzed coagulants in coagulation process is well known for water and wastewater treatment. However, information on the application of pre-hydrolyzed coagulants, especially pre-hydrolyzed iron (PHI), in partially stabilized leachate treatments is not well documented. This study examined the application of PHI on the partially stabilized leachate by determining the optimum basicity ratio, pH, and dose through the removals percentage of suspended solid (SS), color, and chemical oxygen demand (COD). Laboratory jar tests revealed that the optimum PHI basicity ratio, pH, and dosage were 0.1, 5, and 0.2 g/L Fe, respectively. The optimum removals of SS, color, and COD were 99, 95, and 58% respectively. The results indicated that PHI could be potentially useful coagulant for removing SS, color, and COD from partially stabilized landfill leachate.

AbstractLeachate is a major pollution source associated with municipal solid waste landfill. This study was carried out to evaluate the effectiveness of various techniques in treating mature landfill leachate generated from landfill in Malaysia, a tropical country. Treatment processes such as biological, ion exchange, coagulation–flocculation, adsorption, advanced oxidation processes (AOPs), and flotation were analyzed. The efficiency of each process was analyzed based on chemical oxygen demand (COD), color, and NH3-N percentage removals. Ion exchange treatment via cationic/anionic sequence achieved the best removal of color (96.8%), COD (87.9%), and NH3-N (93.8%) from leachate as compared with other treatment methods. Coagulation–flocculation and AOPs were successful for COD and color removals from leachate. However, both could not treat NH3-N effectively. Biological treatment could remove NH3-N (71%) effectively, but it was poor in terms of COD (29%) and color (22%) removals. Adsorption via a new carbon–mineral composite exhibited better removal of both COD (68.4%) and NH3-N (92.6%) from stabilized leachate.

Leachate is a major pollution source associated with municipal solid waste landfill. This study was carried out to evaluate the effectiveness of various techniques in treating mature landfill leachate generated from landfill in Malaysia, a tropical country. Treatment processes such as biological, ion exchange, coagulation–flocculation, adsorption, advanced oxidation processes (AOPs), and flotation were analyzed. The efficiency of each process was analyzed based on chemical oxygen demand (COD), color, and NH3-N percentage removals. Ion exchange treatment via cationic/anionic sequence achieved the best removal of color (96.8%), COD (87.9%), and NH3-N (93.8%) from leachate as compared with other treatment methods. Coagulation–flocculation and AOPs were successful for COD and color removals from leachate. However, both could not treat NH3-N effectively. Biological treatment could remove NH3-N (71%) effectively, but it was poor in terms of COD (29%) and color (22%) removals. Adsorption via a new carbon–mineral composite exhibited better removal of both COD (68.4%) and NH3-N (92.6%) from stabilized leachate.

One of the main contributors to the waste generated in the Malaysian construction industry is housing projects. The main issues in this area are the lack of concern on the causes and contributory factors of waste generated. The objective of this study is to explore the causes and contributory factors that cause waste to be generated according to the material activity for the major waste generated in the housing construction sites. The identification of the waste causes by the material is significant as waste source detection. The methodology used in this study is site observations and interviews with the site personnel. The study found the similarity in term of the two major contributors; the management and the workers. From the study, the factors that cause waste to be generated are highlighted and the waste site checklist according to the material can be developed as a guideline for the site personnel and site management.

This article reviewed selected works on how decision makers (DMs) utilize integrated geographic information system (GIS)/analytical hierarchy process (AHP) tools to analyze land suitability for sanitary landfill sites as part of regional planning. We analyzed the hierarchy process of certain pervious works to facilitate better understanding. The innovative work of Siddiqi et al. in 1996 highlighted the advantages of integrating AHP in GIS software and reviewed some limitations. The present paper explained the background study on multi-criteria decision analysis/aid (MCDA) so-called multi-criteria decision makers (MCDM) in conjunction with the advantages of GIS as a new remedy for utilizing the AHP weights of the decision makers. For this study we often use the term MCDA and MCDM.

Understanding the characteristic of leachate is important since it has complexity properties because of the variation in its composition. This study, analyzed and compared two leachate from two landfill sites, namely, Matang and Kuala Sembeling landfill. Leachate raw samples were collected by grab sampling and were analyzed for 11 parameters. The average concentrations of MLS and KSLS leachate such as BOD5 (146 and 61 mg/L), COD (828 and 363 mg/L), pH (7.6 and 8), SS (407 and 220 mg/L), ammonia (868 and 367 mg/L) , BOD/COD (0.18 and 0.14), cadmium (0.19 and 0.1 mg/L), cuprum (0.09 and 0.1 mg/L), nickel (0.17 and 0.1 mg/L), manganese (0.09 and 0.22 mg/L), and ferum (2.3 and 8.3 mg/L) were recorded, respectively. The results revealed that the both landfills are categorized as partially stabilized leachate. The strength of leachate pollutants from MLS are higher than KSLS because of the higher fraction of organics concentration. There are 5 parameters (BOD5, COD, ammonia, SS and cadmium) in MLS and 7 parameters (BOD5, COD, ammonia, SS, cadmium, manganese and ferum) in KSLS exceeded the permissible limit stated by MEQA (1974), and so leachates from both landfill sites need a suitable treatment to reduce the concentration of the leachate pollutants before discharge into environment.

The reduction of the duration of start-up and the improvement of process control are important factors in order to increase the competitiveness of anaerobic baffled reactor systems. In this paper, the start-up performance of modified anaerobic baffled reactor (MABR) in treating recycled paper mill (RPM) wastewater at batch and continuous phases was investigated. In batch phase, about 3.5L (10d HRT) of RPM wastewater were added daily to the reactor for 9 days, while 7L/day (5d HRT) was pumped into the reactor during the continuous phase. During batch and continuous phase, it was found that methane yield increased significantly from 0.003 to 0.09 L CH4/g COD day. During the whole start-up operation, the system demonstrated a remarkable performance of high COD removal efficiency (up to 71%) on day 30. Nevertheless, the pH was slightly decreased (from 7.3 to 6.2) during the period of phase 1 (batch) and phase 2 (continuous).

AbstractAmong numerous techniques, electro-oxidation occupies a noticeable place in landfill leachate treatment. In recent years, electro-oxidation processes have been shown to be effective alternative for the removal of refractory organic compounds from stabilized landfill leachate. This paper aims to provide an overview about the effectiveness and mechanism of electro-oxidation processes employed for stabilized landfill leachate treatment. A review of the recent literature published on the electro-oxidation processes (i.e. electrochemical, electro-Fenton, photoelectro-Fenton, photoelectrochemical, and electrochemical peroxidation) performance and efficiency in stabilized leachate treatment are summarized and presented in this study. This study concluded that, although the high treatment cost caused by the energy consumption may limit electro-oxidation techniques, electro-oxidation processes are still a promising and effectual technology for the reduction of pollutants in stabilized landfill leachate.

AbstractHibiscus rosa-sinensisis a biodegradable material that has not yet been tested for its flocculating properties. The objective of this study was to examine the efficiency of coagulation–flocculation processes for the removal of suspended solids (SS) from landfill leachate using aluminium sulphate (alum) and Hibiscus rosa-sinensisleaves extract at different pH and dosages. The experiments confirmed the positive coagulation properties of the investigated natural coagulant. The extracts from Hibiscus rosa-sinensisleaves had an isoelectric point at pH 4 and acted as a bridging mechanism in removing 74% of SS (8,000 mg/L dosage at pH 6) which was comparable with 78% SS removal using 7,000 mg/L alum (at pH 6).

Hibiscus rosa-sinensisis a biodegradable material that has not yet been tested for its flocculating properties. The objective of this study was to examine the efficiency of coagulation–flocculation processes for the removal of suspended solids (SS) from landfill leachate using aluminium sulphate (alum) and Hibiscus rosa-sinensisleaves extract at different pH and dosages. The experiments confirmed the positive coagulation properties of the investigated natural coagulant. The extracts from Hibiscus rosa-sinensisleaves had an isoelectric point at pH 4 and acted as a bridging mechanism in removing 74% of SS (8,000 mg/L dosage at pH 6) which was comparable with 78% SS removal using 7,000 mg/L alum (at pH 6).

Among numerous techniques, electro-oxidation occupies a noticeable place in landfill leachate treatment. In recent years, electro-oxidation processes have been shown to be effective alternative for the removal of refractory organic compounds from stabilized landfill leachate. This paper aims to provide an overview about the effectiveness and mechanism of electro-oxidation processes employed for stabilized landfill leachate treatment. A review of the recent literature published on the electro-oxidation processes (i.e. electrochemical, electro-Fenton, photoelectro-Fenton, photoelectrochemical, and electrochemical peroxidation) performance and efficiency in stabilized leachate treatment are summarized and presented in this study. This study concluded that, although the high treatment cost caused by the energy consumption may limit electro-oxidation techniques, electro-oxidation processes are still a promising and effectual technology for the reduction of pollutants in stabilized landfill leachate.

This research examined various experimental conditions for application of Polyaluminium Chloride (PAC) for removing colour, COD and ammonia from semi-aerobic. The removals of colour, COD and ammonia were up to 93%, 56% and 32%, respectively, at an optimum dosage of 2000 mg/L PAC. Rapid and slow mixing speed played only a minor role in the removal efficiencies for colour, COD and ammonia. The flocs size distribution for PAC coagulant shows an increase in floc size with increasing coagulant dosages. PAC also exhibited excellent settling characteristics, with majority of the flocs settled out in the initial 5 min of settling.