Anaerobic digestion (AD) appears to be a popular unit operation in wastewater treatment plant to treat waste activated sludge (WAS) and the produced methane gas can be harvested as renewable energy. However, WAS could inhibit hydrolysis stage during AD and hence pre-treatment is required to overcome the issue. This paper aimed to study the effect of electrochemical pre-treatment (EP) towards efficiency of AD using titanium coated with ruthenium oxide (Ti/RuO2) electrodes. The investigation has been carried out using in-house laboratory batch-scale mesophilic anaerobic digester, mixed under manipulation of important operating parameters. Optimization was performed on EP using response surface methodology and central composite design to maximize sludge disintegration and dewaterability. By operating at optimal conditions (pH 11.65, total solids 22,000 mg/L, electrolysis time 35 min, current density 6 mA/cm2, and 1000 mg/L of sodium chloride), the pre-treated WAS in terms of mixed liquor volatile suspended solids (MLVSS) removal, soluble chemical oxygen demand (sCOD), capillary suction time (CST) reduction, and extracellular polymeric substance (EPS) were 38%, 4800 mg/L (increased from 935 mg/L), 33%, and 218 mg/L, respectively. Following AD, the volatile solids (VS) removal and chemical oxygen demand (COD) removal by EP were enhanced from 40.7% and 54.7% to 47.2% and 61.5%, respectively, at steady-state. The biogas produced from control and electrochemical pre-treated WAS were in the ranges of 0.12 to 0.17 and 0.2 to 0.24 m3/kg VSfed, respectively, and the volume of biogas produced was 44–67% over the control. Based on the results obtained, suitability of EP for WAS prior to AD was confirmed.

Biological treatments, such as activated sludge process, are common methods to treat municipal and industrial wastewaters. However, they produce huge amounts of waste activated sludge (WAS). The excess sludge treatment and disposal are a challenge for wastewater treatment plants due to economic, environmental, and regulatory factors. In this study, photo-Fenton pretreatment (oxidation using hydrogen peroxide and iron catalyst aided with UV light) was optimized using response surface methodology (RSM) and central composite design (CCD) to determine the effects of three operating parameters (HO dosage, HO/Fe molar ratio, and irradiation time) on disintegration and dewaterability of WAS. MLVSS removal, capillary suction time (CST) reduction, sCOD, and EPS were obtained as 70%, 25%, 12,000 mg/L, and 500 mg/L, respectively, at the optimal conditions, i.e., 725 g HO/kg TS, HO/Fe molar ratio 80, and irradiation time 40 min. Two batch-fed completely mixed mesophilic anaerobic digesters were then operated at 15-day solid retention time (SRT) and 37 ± 0.5 °C to compare the digestibility of untreated and photo-Fenton pretreated sludge in terms of volatile solids (VS) reduction, COD removal, and biogas production at steady-state operations. Photo-Fenton pretreatment followed by anaerobic digestion of WAS was very effective and yielded 75.7% total VS reduction, 81.5% COD removal, and 0.29-0.31 m/kg VS·d biogas production rate, compared to 40.7% total VS solid reduction, 54.7% COD removal, and 0.12-0.17 m/kg VS·d biogas production rate for control. Thus, photo-Fenton can be a useful pretreatment step in sludge management.

Incorporation of inorganic fillers into Polysulfone (PSF) to constitute mixed matrix membranes (MMMs) has become a viable solution to prevail over limitations of the pristine materials in natural gas sweetening process. Nevertheless, preparation of MMMs without defects and empirical investigation of

Rubber product manufacturing industry was found with severe occupational noise exposure problems due to improper noise management and lack of reliable noise information at the workplace. Strategic noise mapping provides important information in monitoring the occupational noise. Therefore, a case study was conducted to investigate the current noise exposure circumstances based on the information from the noise map and noise risk zones. The stochastic noise mapping simulation method was applied to predict these maps. Based on the results, most of the regions in the operation area were bounded with a noise contour level of 80 dBA and some small regions were exceeded the noise level of 100 dBA. More than 45 % of mapping area was categorised as extremely high risk and high risk zones. Workers are exposed to the high noise level in this workplace. The management should take immediate action for controlling noise and always supervise their workers in using the hearing protection equipment.

Biological-based treatment being the conventional treatment for palm oil mill effluent (POME) in open-ponding system faced a well-known rate-limiting step which is hydrolysis. In this study, electrochemical oxidation (EO) by ruthenium oxide coated titanium (Ti/RuO2) electrode was introduced as a pre-treatment for POME waste activated sludge (WAS). Surface morphology and elemental analysis were investigated by Field Emission Scanning Electron Microscopy and Energy Dispersive X-Ray, respectively. Response surface methodology type central composite design was used in this study to understand the relationship between the independent and dependent variables. Analysis of variance (ANOVA) was used to validate the model of the studied variables. The correlation coefficients (R2) indicated a close agreement between experimental results and predicted values, with high R2 values of 0.9044–0.9773. Multiple response optimization suggested that the range of current density (17–27 mA/cm2) and electrolysis time (55–75 min) at a fixed concentration of sodium chloride (10 g/L), resulting in mixed liquor volatile suspended solids (MLVSS) removal >20%, capillary suction timer (CST) reduction >43%, extracellular polymeric substances (EPS) increment <19% and soluble chemical oxygen demand (sCOD) increment >25%. EO appears to be an efficient pre-treatment as well as practical to improve the POME WAS disintegration and dewaterability.