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In this study, four coagulants were used to investigate their performances for the treatment of raw landfill leachate. Two inorganic coagulants, namely, ferric sulfate, Fe2 (SO4 )3 and zinc sulfate, ZnSO4 were compared to two types of palm date seeds, that is, khlas and sukkari as natural coagulants. Type of coagulant, dosage, pH and rapid mixing speed were designated as input variables, that is, operating conditions. In order to determine and compare the leachate treatment performances of the four coagulants, four responses were selected for this research, namely, chemical oxygen demand (COD), color, ammoniacal nitrogen (NH3 –N) or simply ammonia and total suspended solids (TSS). A response surface model (RSM) was developed for each selected response to find the optimum operating conditions for the input variable and for each coagulant that result in maximum removals. 72 experiments under different operating conditions were performed of which 18 runs were conducted for each type of coagulant wherein 100 mL of raw landfill leachate was the sample volume used for each run. The optimum operating conditions were found in the models and experimentally validated. The optimum dosage of ferric sulfate, zinc sulfate and khlas was found to be 6 mL. However, a lower dosage of 4.32 mL was found to be the optimum for sukkari. The optimal pH for ferric sulfate and sukkari was 5, whilst a pH of 9 was obtained for khlas and zinc sulfate. Finally, the optimum rapid mixing speeds for khlas and sukkari were rounded off to 195 and 200 rpm, respectively. Meanwhile, higher optimal rapid mixing speeds of 240 and 250 rpm were rounded out for ferric sulfate and zinc sulfate, correspondingly. Hence, the optimal reductions of COD, color, ammonia and TSS by (ferric sulfate–zinc sulfate) were rounded off to 55%–53%, 89%–73%, 15%–17% and 91%–89%, respectively. On the other hand, the optimum removals obtained by the natural coagulants (khlas–sukkari) were as the following: 12%–15% COD, 53%–56% color, 12%–14% ammonia and 78%–67% TSS. As regards the maximum removals of COD, color, ammonia and TSS by (ferric sulfate–zinc sulfate), they were found and rounded off to 60%–60%, 89%–84%, 18%–21% and 95%–96%, respectively. Contrariwise, the maximum reductions obtained by the natural coagulants (khlas–sukkari) were as the following: 16%–24% COD, 70%–74% color, 17%–17% ammonia and 91%–82% TSS. Thereupon, the natural coagulants showed effective removals, notably in terms of color, ammonia and TSS that could adequately replace the inorganic coagulants. A big margin of improvement in the removal of COD and other pollutants by khlas and sukkari could possibly be achieved in the upcoming studies by extensively investigating the preparation techniques of the natural coagulants. [ABSTRACT FROM AUTHOR]

The performance of seven oxidation treatments on stabilized landfill leachate namely; O3, Fenton, Fenton followed by O3, persulfate, persulfate followed by O3, simultaneous O3/Fenton, and simultaneous O3/persulfate were evaluated and compared. The study aims to assess the variation between all the seven oxidation treatments with regards to COD and color removal. The analysis of variance (ANOVA) and Tukey's test showed that there were significant differences between the performances of the treatments. The O3 treatment removed the lowest COD and color while the simultaneous O3/Fenton, Fenton followed by O3, simultaneous O3/persulfate and persulfate followed by O3 removed the highest. Hence, these treatments are recommended to remove organics from stabilized landfill leachate. [ABSTRACT FROM AUTHOR]

The aim of the current study is to evaluate the effectiveness of combined persulphate with hydrogen peroxide (S2O82-/H2O2) oxidation as a post-treatment of biologically treated palm oil mill effluent (POME) for the first time in the literature. The removal efficiencies of chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N), and suspended solids (SS) were 36.8%, 47.6%, and 90.6%, respectively, by S2O82- oxidation alone under certain operation conditions (i.e., S2O82- = 0.82 g, pH 11, and contact time 20 min). Nevertheless, the combined process (S2O82-/H2O2) achieved 75.8% and 87.1% removals of NH3-N and SS, respectively, under 2.45/1.63 g/g H2O2/S2O82-, pH 11, and 20 min oxidation. Moreover, 56.9% of COD was removed at pH 8.4. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the performance of combined solar photo-catalyst of titanium oxide/zinc oxide (TiO2/ZnO) with aeration processes to treat petroleum wastewater. Central composite design with response surface methodology was used to evaluate the relationships between operating variables for TiO2 dosage, ZnO dosage, air flow, pH, and reaction time to identify the optimum operating conditions. Quadratic models for chemical oxygen demand (COD) and total organic carbon (TOC) removals prove to be significant with low probabilities (<0.0001). The obtained optimum conditions included a reaction time of 170 min, TiO2 dosage (0.5 g/L), ZnO dosage (0.54 g/L), air flow (4.3 L/min), and pH 6.8 COD and TOC removal rates of 99% and 74%, respectively. The TOC and COD removal rates correspond well with the predicted models. The maximum removal rate for TOC and COD was 99.3% and 76%, respectively at optimum operational conditions of TiO2 dosage (0.5 g/L), ZnO dosage (0.54 g/L), air flow (4.3 L/min), reaction time (170 min) and pH (6.8). The new treatment process achieved higher degradation efficiencies for TOC and COD and reduced the treatment time comparing with other related processes. [ABSTRACT FROM AUTHOR]

As the ponding system used to treat palm oil mill effluent (POME) frequently fails to satisfy the discharge standard in Malaysia, the present study aimed to resolve this problem using an optimized electrocoagulation process. Thus, a central composite design (CCD) module in response surface methodology was employed to optimize the interactions of process variables, namely current density, contact time and initial pH targeted on maximum removal of chemical oxygen demand (COD), colour and turbidity with satisfactory pH of discharge POME. The batch study was initially designed by CCD and statistical models of responses were subsequently derived to indicate the significant terms of interactive process variables. All models were verified by analysis of variance showing model significances with Prob >F< 0.01. The optimum performance was obtained at the current density of 56 mA/cm2, contact time of 65 min and initial pH of 4.5, rendering complete removal of colour and turbidity with COD removal of 75.4%. The pH of post-treated POME of 7.6 was achieved, which is suitable for direct discharge. These predicted outputs were subsequently confirmed by insignificant standard deviation readings between predicted and actual values. This optimum condition also permitted the simultaneous removal of NH3-N, and various metal ions, signifying the superiority of the electrocoagulation process optimized by CCD. [ABSTRACT FROM AUTHOR]

This study investigated the effects of O3 and O3/S2O82− in the advanced oxidation process (AOPs) on the biodegradable and soluble characteristics of semiaerobic stabilized solid waste leachate. The biodegradability (BOD5/COD) ratio improved from 0.034 to 0.05 and 0.29 following O3 and O3/ S2O82−, respectively. Fractions of biodegradable COD(bi) (24%), nonbiodegradable COD(ubi) (76%), soluble COD(s) (59%), biodegradable soluble COD(bsi) (38%), nonbiodegradable soluble COD(ubsi) (62%), and particulate COD (PCOD) (41%) in stabilized leachate were also investigated. The fraction of COD (bi) increased to 28 and 39% after applying O3 and O3/ S2O82− in AOPs, respectively. COD(S) increased to 65 after O3 and to 72% after O3/AOPs, whereas COD (bsi) increased to 38 and 55% after O3 and O3/AOPs, respectively. The removal efficiency of total COD was obtained at 15 after O3 alone and improved to 72% following ozone-based AOPs, whereas PCOD reduced from 41 to 35 after O3 and 28% after ozone-based AOPs. Ozone/Prsulfate is an efficient method for degradation of stabilized leachate, enhanced biodegradability and improved biodegradable and soluble characteristics of stabilized leachate. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 184-191, 2014 [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to investigate the performance of employing persulfate reagent in the advanced oxidation of ozone to treat stabilized landfill leachate in an ozone reactor. A central composite design (CCD) with response surface methodology (RSM) was applied to evaluate the relationships between operating variables, such as ozone and persulfate dosages, pH, and reaction time, to identify the optimum operating conditions. Quadratic models for the following four responses proved to be significant with very low probabilities (<0.0001): COD, color, NH3–N, and ozone consumption (OC). The obtained optimum conditions included a reaction time of 210min, 30g/m3 ozone, 1g/1g ratio, and pH 10. The experimental results were corresponded well with predicted models (COD, color, and NH3–N removal rates of 72%, 96%, and 76%, respectively, and 0.60 (kg O3/kg COD OC). The results obtained in the stabilized leachate treatment were compared with those from other treatment processes, such as ozone only and persulfate only, to evaluate its effectiveness. The combined method (i.e., ) achieved higher removal efficiencies for COD, color, and NH3–N compared with other studied applications. Furthermore, the new method is more efficient than ozone/Fenton in advanced oxidation process in the treatment of the same studied leachate. [Copyright &y& Elsevier]

The objective of this study was to investigate the performance of employing Fenton's reagent in the advanced oxidation of ozone to treat stabilized landfill leachate in an ozone reactor. A central composite design (CCD) with response surface methodology (RSM) was applied to evaluate the relationships between operating variables, such as ozone and Fenton dosage, pH, and reaction time, to identify the optimum operating conditions. Quadratic models for the following four responses proved to be significant with very low probabilities (<0.0001): chemical oxygen demand (COD), color, NH3–N, and ozone consumption (OC). The obtained optimum conditions included a reaction time of 90 min, 30 g/m3ozone, 0.01 mol/LH2O2,0.02 mol/L Fe2+, and pH 5. COD, color, and NH3–N removal rates of 79%, 100%, and 20%, respectively, and 0.18 kg O3/kg COD OC were obtained. The predictions correspond well with experimental results (COD, color, and NH3–N removal rates of 78%, 98.5%, and 19%, respectively, and 0.29 kg O3/kg COD OC). This method reduces the treatment time and improves the treatment efficiency relative to a previously published method that used Fenton's reagent prior to ozonation. [ABSTRACT FROM AUTHOR]

Abstract: A combination of ozonation and persulfate was used to treat stabilized landfill leachate. COD, color, and NH3–N, ozone and persulfate doses, pH and reaction time were evaluated to define the optimum operational conditions. The results indicated that under optimum operation conditions (i.e. 210min of ozonation, a ratio (1g/7g), and pH 10), the best removal values of COD, color, and NH3–N were 72%, 93%, and 55%, respectively. The biodegradability (BOD5/COD ratio) has improved from 0.05 to 0.29. The ozone consumption for COD removal was 0.76kg O3/kg COD. The results obtained by employing the combined use of persulfate and ozone were compared with those by employing ozone only and persulfate only. The results achieved with the combined use of persulfate and ozone were compared with those obtained with ozone only and persulfate only. The combined method (i.e., ) achieved higher removal efficiencies for COD, color, and NH3–N compared with other studied applications. Additionally, the combined of ozone/persulfate method proved to be more efficient than the combined use of ozone/Fenton in advanced oxidation processes in the treatment of the same studied leachate. [Copyright &y& Elsevier]

Abstract: Ozonation, combined with the Fenton process (O3/H2O2/Fe2+), was used to treat matured landfill leachate. The effectiveness of the Fenton molar ratio, Fenton concentration, pH variance, and reaction time were evaluated under optimum operational conditions. The optimum removal values of chemical oxygen demand (COD), color, and NH3–N were found to be 65%, 98%, and 12%, respectively, for 90min of ozonation using a Fenton molar ratio of 1 at a Fenton concentration of 0.05molL−1 (1700mg/L) H2O2 and 0.05molL−1 (2800mg/L) Fe2+ at pH 7. The maximum removal of NH3–N was 19% at 150min. The ozone consumption for COD removal was 0.63kg O3/kg COD. To evaluate the effectiveness, the results obtained in the treatment of stabilized leachate were compared with those obtained from other treatment processes, such as ozone alone, Fenton reaction alone, as well as combined Fenton and ozone. The combined method (i.e., O3/H2O2/Fe2+) achieved higher removal efficiencies for COD, color, and NH3–N compared with other studied applications. [Copyright &y& Elsevier]

In this study, tannin-based natural coagulant was used to treat stabilized landfill leachate. Tannin modified with amino group was utilized for the treatment process. Central composite design (CCD) was used to investigate and optimize the effect of tannin dosage and pH on four responses. The treatment efficiency was evaluated based on the removal of four selected (responses) parameters; namely, chemical oxygen demand (COD), color, NH3–N and total suspended solids (TSS). The optimum removal efficiency for COD, TSS, NH3–N and color was obtained using a tannin dosage of 0.73 g at a pH of 6. Moreover, the removal efficiency for selected heavy metals from leachate; namely, iron (Fe2+), zinc (Zn2+), copper (Cu2+), chromium (Cr2+), cadmium (Cd2+), lead (Pb2+), arsenic (As3+), and cobalt (Co2+) was also investigated. The results for removal efficiency for COD, TSS, NH3–N, and color were 53.50%, 60.26%, and 91.39%, respectively. The removal of selected heavy metals from leachate for Fe2+, Zn2+, Cu2+, Cr2+, Cd2+, Pb2+, As3+ and cobalt Co2+ were 89.76%, 94.61%, 94.15%, 89.94%, 17.26%, 93.78%, 86.43% and 84.19%, respectively. The results demonstrate that tannin-based natural coagulant could effectively remove organic compounds and heavy metals from stabilized landfill leachate. [ABSTRACT FROM AUTHOR]

Hybrid coagulants have recently received attention in water and wastewater treatment technologies mainly due to their cost-efficiency and exceptional performance. As such, this study highlights the recent advanced applications of hybrid coagulants in wastewater treatment. The materials used for hybrid coagulants, such as those hybridised in chemical bond, structurally-hybridised, and functionally-hybridised under certain combination techniques (e.g., organic/inorganic, organic/organic, inorganic/inorganic, organic/natural polymer, inorganic/natural polymer, organic/biopolymer, & inorganic/biopolymer), were evaluated and compared based on their applications on different type of wastewaters, experimental conditions, and treatment efficiency. The performance of inorganic/inorganic hybrid coagulation demonstrated high removal of turbidity (98.5%), chemical oxygen demand (COD) (73.3%), heavy metals (99.2%), and colour (98%) - seemingly better than organic removal efficiency. The optimum operational conditions for inorganic/organic coagulants at varied pH levels (6–12) lowered the cost for chemicals used for pH adjustment in treating industrial wastewater. Referring to the review outcomes, hybrid coagulation applications are indeed efficient for treatment of highly concentrated industrial wastewater, such as oily wastewater. • The efficiency of using hybrid coagulants in wastewater treatment. • The performance of inorganic/inorganic hybrid coagulates shows high efficiency. • Hybrid coagulants are more efficient, environmentally friendly, cost-efficiency. • Cost-efficient hybrid materials are promising for industrial purposes. [ABSTRACT FROM AUTHOR]

A large volume of concentrated leachate is generated from leachate treatment via reverse osmosis. Concentrated leachate is a dark brown solution with high levels of pollutants. Treating concentrated leachate is extremely difficult, and thus, a combined treatment system is suggested. In the present study, concentrated landfill leachate was treated using a combined treatment technique that included electro-ozonation and a composite adsorbent augmented sequencing batch reactor (SBR) process. Central composite design and response surface methodology were utilized to investigate experimental data. Reaction time (30–120 min) and ozone concentration (40–120 mg/L) were selected as the independent variables. At an optimum reaction time (96.9 min) and ozone dosage (120.0 mg/L), the removal efficacies of chemical oxygen demand (COD), color, and nickel were 64.8%, 90.4%, and 52.9%, respectively, at original pH (7.3), as well as current and voltage of 4 A and 9 V, respectively. Ozone utilization ranged from 0.3 kg to 1.4 kg COD removed per kg ozone consumed. After treatment at optimum electro-ozonation performance, concentrated leachate was transferred to the powdered composite adsorbent (P-BAZLSC) augmented SBR reactor (PB-SBR). PB-SBR improved the removal efficiency for COD, color, and nickel from 64.8% to 88.2%, from 90.4% to 96.1%, and from 52.9% to 73.4%, respectively. [ABSTRACT FROM AUTHOR]