Applied Mechanics and Materials Vol. 802

Abstract: 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.

Abstract: Landfill still remains the most commonly employed treatment for municipal solid waste disposal around the world, which generates a high-strength wastewater with complex constituents referred to as landfill leachate. As consequences, if not properly treated and safely disposed, leachate can migrate into soil and subsoils which might cause severe damage to eco-system of land, surface water and groundwater. Aim of this paper is to establish the optimum parameters of starch-based coagulant as an alternative coagulant to remove suspended solid (SS), colour, turbidity, carbon oxygen demand (COD), and ammoniacal-nitrogen in leachate treatment by using RSM method. Leachate was collected from Matang Landfill Site, Perak, Malaysia. In this paper, the efficiency of Jackfruit seeds starch (JSS) act as a coagulant aid is established by using Kategunya method with percentage yield of 33.67%. The starch obtained is then used together with polyaluminium chloride (PAC) in leachate sample. The removal efficiency was determined by a series of experiments using jar test. By using three independent variables including pH, dosage of PAC and dosage of JSS for Central Composite Design (CCD) of RSM, optimum removal of response parameters is carried out. As a result, optimum removal of COD at pH 5, 523.32 mg/L of PAC, 400 mg/L of JSS gives Prob.>F significantly with only 4.32% error. The results showed that, addition of JSS as coagulant aid also helps to reduce the dosage of PAC as well as JSS in leachate. As a conclusion, JSS can be used as a coagulant aid to PAC.

Abstract: Abstract. In order to provide a better understanding of the Orbal Biological System (OBS), as one type of a modified oxidation ditch, the research aims to develop a preliminary process model to visualize the oxygen uptake by biological processes inside the oxidation ditch. Fundamentally, the model can be used as initial study to get a clearer picture of the oxygen utilization rate inside the ditch. Based on the results, the outer channel takes the highest portion of the overall oxygen consumption which is 66 % compare to the middle channel with only 14 % and followed by the inner channel with 20 %. However, simplifying assumptions made for the preliminary process model development (e.g. constant values of HRT throughout each channel) may affect the accuracy of describing the real conditions of the system.

Abstract: Some unfortunate accidents of large amount of oil hydrocarbons have been reported in Mediterranean Sea which has caused severe environmental damage to the area. To safeguard the Libyan coastline and marine ecologysince thousands of human activity such as fishing largely depends on the healthycoastal environment.Twenty crude oil-degrading bacterial isolates were obtained from oil-contaminated sites at Al Hariga Oil Terminal and Nafoora Oilfield. Based on a high growth rate in crude oil and hydrocarbon degradation efficiency, two isolates were selected from the twenty isolates for further analysis. The nucleotide sequence of 16S rRNA gene showed that these isolates are likely Pseudomonas aeruginosa andKocuriapastrius. One of the isolates is a potential Gram-negative Pseudomonas bacterium based on petroleum hydrocarbon degradation efficiency and potent emulsifying activity; thus, this isolate is identified as P. aeruginosa NAF1; the other isolate K. pastrius SAR3 is identified as a Gram-positive bacterium. Corn steep liquor (CSL) and solid waste date (SWD) were used for an in situ molasses technique to enhance bacterial growth and biodegradation efficiency. P. aeruginosa NAF1 exhibited 70% and 76% crude oil degradation in 0.2% (w/v) CSL and SWD in 28 d, respectively. Likewise, K. pastrius SAR3 yielded 68% and 70% crude oil degradation in 0.2% (w/v) CSL and SWD in 28 d, respectively.

Abstract: Landfill leachate generation is one of the main problems from sanitary landfill. Chemical oxygen demand (COD), ammoniacal nitrogen (NH₃-N), and color are among the most problematic parameters in stabilized leachate. In this regard, dedicated treatment facilities are required before leachate can be discharged into the environment. The performance of the combined ozonation (O₃) and zirconium tetrachloride (ZrCl₄) to treat two types of stabilized leachate was investigated during this study. Leachate samples were collected from an anaerobic stabilized leachate (Alor Pongsu Landfill Site, APLS) and semi-aerobic stabilized leachate (Pulau Burung Landfill Site, PBLS). Zirconium tetrachloride dosage was determined as 1 g/1 g (COD/ZrCl₄ ratio) and then added to the leachate samples with 60 min ozonation at natural leachate pH (8). COD, color, and NH₃-N were removed from the APLS sample at 33%, 70%, and 53% rates, respectively, whereas 48%, 75%, and 69%, respectively, from the PBLS samples. Ozone consumption was also calculated with the highest value (3.81 Kg O₃/ Kg COD) reported in PBLS, whereas the lowest value (2.32 Kg O₃/ Kg COD) was reported in APLS. Biodegradability of (BOD₅/COD) was investigated and improved from 0.07 to 0.08 for the APLS samples and 0.05 to 0.11 for the PBLS samples after leachate oxidation. Results showed that the performance of O3/ZrCl₄ oxidation is more efficient in treating semi-aerobic stabilized leachate than anaerobic stabilized leachate Moreover, the combined method proved to be more efficient in remediating leachate compared with ozone and zirconium treatment alone.

Abstract: Compound Parabolic Collecting Reactor (CPCR) was designed and used for the heterogeneous-photocatalytic treatment process. Sunray was act as an economically and ecologically sensible light source. The photocatalytic degradation of paracetamol in the synthetic wastewater by using titanium dioxide (TiO₂) was investigated. The experimental results show that the paracetamol removal rates were very high and nearly equal (97.2% to 99.7%) at pH 4-7 and TiO₂ concentration of 0.5-1 g/L. This implies that the photocatalytic degradation rate of paracetamol is not affected by pH range in this study as the electrostatic interaction between the TiO₂ and paracetamol is not able to be developed unless a wider range of pH is set. Furthermore, the concentration of TiO₂ of 0.5 g/L is too high to treat the concentration of 10 mg/L of paracetamol. Further research is needed in order to identify the optimum pH condition and a suitable correlation of concentration between TiO₂ and paracetamol. Finally, the results proved that the heterogeneous-photocatalyst treatment method which associated with the application of CPCR and solar energy is able to eliminate the paracetamol from the synthetic wastewater.

Abstract: Natural organic matter (NOM) in water reacts with chlorine or other disinfectants and form hazardous disinfectant by-products (DBPs). This study aimed to detect the presence of NOM in a conventional water distribution system using UV absorbance at 254 nm as a surrogate. Two water treatment plants were selected, namely, Jalan Baharu Water Treatment Plant (JBWTP) and Lubok Buntar Water Treatment Plant (LBWTP). Aside from determining the amount of NOM, the reduction of UV₂₅₄ after completing the series of treatments (coagulation, flocculation, sedimentation, filtration, and disinfection) was also observed. The presence of UV₂₅₄ in both raw water and treated water samples confirmed the presence of NOM. The concentration of UV₂₅₄ recorded at JBWTP and LBWTP were 0.14 and 0.13 cm⁻¹, respectively. After the treatment processes, the concentration was reduced to 0.04 cm⁻¹ for JBWTP and 0.03 cm⁻¹ for LBWTP. These results indicated that the water supply in both plants contains DBP precursors and implied the possibility of DBP formation in the system. Moreover, the percentage reduction of UV₂₅₄ recorded were 69% and 75% for JBWTP and LBWTP, respectively.

Abstract: Sago starch has been widely used in industrial fields, especially in food, non-food, and animal feed biotechnology. Malaysia is one of the highest local sources of sago starch. The alternative use of sago starch as a coagulant for domestic wastewater treatment was investigated in this study. The wastewater sample was collected from the Juru Regional Sewage Treatment Plant in Juru, Penang. The studied parameters include the chemical oxygen demand (COD), suspended solids, and color. Standard jar test procedures were conducted. The initial operating conditions were 200 rpm for 3 min of rapid mixing, 40 rpm for 30 min of slow mixing, and 30 min of settling. The optimum conditions included a pH of 7 and dosage of 2000 mg/L, with rapid mixing at 100 rpm for 1 min, slow mixing at 20 rpm for 30 min, and 18 min of settling. The removal rate of COD and color at these conditions was 70%. Simultaneously, 82% of SS was also removed. The results indicated that sago starch has good potential to treat domestic wastewater; the coagulant may also efficiently treat other types of wastewater.

Abstract: Sanitary landfill is the most common way to eliminate solid waste. However, sanitary landfill generates large quantity of leachate. Leachate can be defined as a liquid that passes through a landfill and extracted dissolved and suspended matter. The presence of large quantity of contaminants in leachate is harmful to human and ecological environment. This can lead to health issues, including gastrointestinal illness, reproductive problems, and neurological disorders. There are several significant techniques have been made to overcome the problem of leachate pollution, including photocatalytic oxidation, adsorption/separation processing and bioremediation. However, the applications have been restricted by many factors, such as processing efficiency, operational method, energy requirements, and economic benefit. This present article provides an overview of research studies and advances concerned with the development of nanoparticles and their potential applications in leachate treatment. Nanoparticles can act as antimicrobial and function as reducing agent and catalyst in detoxification of pollutants in the environment, such as organic, inorganic and heavy metals. NPs have been suggested as efficient, cost-effective and environmental friendly alternative to existing treatment materials and presents a number of potential environmental benefits.

Abstract: The Fe²⁺/modified silica catalysts have been substituted with four types of transition metals such as Fe³⁺, Cr³⁺, Mn³⁺ and Mo. The catalytic activity of these catalysts has been tested for the oxidative degradation of Reactive Black 5 (RB5) at 30°C and pH 4.5. The substituted Fe²⁺/modified silica with Fe³⁺ (Fe²⁺:Fe³⁺/ m-SiO₂) exhibited the highest catalytic performance compared to others transition metals by degrading the RB5 nearly to 95%. This catalyst possessed on high stability by maintaining its performance during the three successive cycles of reaction. These findings can be ascribed to the plausible enhancement in the formation of hydroxyl radicals (HO^●) due to the effective redox between Fe²⁺ and Fe³⁺