Coliform Removal in Membrane Bioreactor and Disinfection during Hospital Wastewater Treatment

This study investigated coliform removal from hospital wastewater in a membrane bioreactor (MBR) and disinfection using either chlorine or ozone. A laboratory-scale MBR equipped with a hollow-fiber membrane module was operated with hydraulic retention times varied at 3 and 6 hours. The disinfection of MBR effluent was carried out using either chlorine or ozone with concentrations varied between 1 and 10 mg/l and contact time varied between 1 and 30 min. During 150 days of MBR operation, organic removal efficiencies averaged 96.5% and 97.7% for BOD and 73.6% and 84.1% during its operation at an HRT of 3 and 6 hours respectively. Simultaneously, 6.7 and 6.4 log reduction of total coliforms and 6.2 and 6.1 log reduction of E. coli were achieved under these respective HRT conditions. The use of chlorine for disinfection of MBR effluent could eliminate total coliforms and E. coli completely at >6 and 3 mg/L at 30 min contact time, whereas only >3 and 1 mg/L was required for ozone at the same contact time. There was a significant improvement of disinfection efficacy of solid-free MBR effluent compared to that of activated sludge effluent

Coliform Removal in Membrane Bioreactor and Disinfection during Hospital Wastewater Treatment

This study investigated coliform removal from hospital wastewater in a membrane bioreactor (MBR) and disinfection using either chlorine or ozone. A laboratory-scale MBR equipped with a hollow-fiber membrane module was operated with hydraulic retention times varied at 3 and 6 hours. The disinfection of MBR effluent was carried out using either chlorine or ozone with concentrations varied between 1 and 10 mg/l and contact time varied between 1 and 30 min. During 150 days of MBR operation, organic removal efficiencies averaged 96.5% and 97.7% for BOD and 73.6% and 84.1% during its operation at an HRT of 3 and 6 hours respectively. Simultaneously, 6.7 and 6.4 log reduction of total coliforms and 6.2 and 6.1 log reduction of E. coli were achieved under these respective HRT conditions. The use of chlorine for disinfection of MBR effluent could eliminate total coliforms and E. coli completely at >6 and 3 mg/L at 30 min contact time, whereas only >3 and 1 mg/L was required for ozone at the same contact time. There was a significant improvement of disinfection efficacy of solid-free MBR effluent compared to that of activated sludge effluent

Economic Assessment of Medium and Large-Scale Landfill Mining Business: Case Study Thailand

Thailand produces over 25 million tons of waste yearly, while only a third is utilized. The waste disposed of in the landfill is rarely utilized, and research on the utilization of landfill waste in Thailand is limited. The information regarding the business model and the profitability rate of landfill mining is limited and generally was not displayed to the public. This paper examined the landfill mining business of medium and large-scale businesses in Thailand. Both sites’ business operations were analyzed, and the net present value was presented. The NPV results show that landfill mining is profitable and gives more sustainable waste management. The large scale is highly profitable but requires more investment extensively, while the medium scale is easily adopted and still provides a reasonable profit. Furthermore, to understand the business operation and sensitivity of the operation, this paper uses sensitivity analysis to analyze the factors influencing business profitability. Even though the result displays that both projects are easily profitable, the large-scale operation tends to be simpler as the expense has a lower influence on the business

Editorial: Special issue on the challenges in environmental science and engineering: CESE-2012 9-13 September 2012, RACV City Club, Melbourne, Australia

This special issue carries selected peer-reviewed manuscripts based on the presentations made at CESE-2012, the Fifth Annual International Conference on Challenges in Environmental Science & Engineering , CESE Conference Series that was held from the 9th to the 13th of September 2012 at the RACV City Club in Melbourne, Australia

Exploring Effective Bio-Cover Materials for Mitigating Methane Emission at a Tropical Landfill

Methane emission and oxidation in different bio-cover materials, i.e., sandy loam, compost, and stabilized wastes, were investigated at a municipal solid waste landfill in Thailand. The bio-cover was purged with extracted landfill gas while methane reduction through biological oxidation was studied. The moisture content in bio-cover materials was maintained with natural rainwater during the wet period and leachate irrigation during the dry period. Methane emissions were found to vary between media and were influenced by rainfall. The methane loading rates of the bio-cover varied from 8.2–20.3 mol/m3/d, being higher during the dry period. Methane removal rates at the bottom part of the biofilter (0.4–0.6 m depth), the most active zone, were found to be from 6.4–10.9 and 7.8–11.4 mol/m3/d during wet and dry periods. The highest methane removals were found in the lower part of sandy loam, followed sequentially by compost and stabilized wastes. Nevertheless, compost had the highest methane oxidation capacities and greater methanotroph population compared to sandy loam and stabilized wastes. Methanotroph type I was found to predominate during the dry period, whereas methanotroph type II was predominant during the wet period

Optimization of Aeration for Accelerating Municipal Solid Waste Biodrying

Biodrying technology is commonly used in Thailand to produce refuse-derived fuel (RDF), however, this technology remains ineffective on high-moisture waste. Air supply is key to ensuring homogenous temperature development within the waste matrix during biodrying, increasing RDF quality. This study investigated negative aeration during local municipal solid waste biodrying to meet RDF standards in reduced time. Lysimeter experiments were performed on pre-shredded waste (300 kg/m3) using different aeration patterns. The temperature, vent gas oxygen level, weight loss, and leachate volume during the biodrying process were monitored. In addition, the treated waste’s temperature, moisture, and heating values were evaluated to determine the biodrying process efficiency. The results indicate that shorter heating phases can be achieved during continuous aeration. No significant temperature variation was observed in the waste layers, with a low standard deviation of 1.96% during constant air supply, indicating homogeneous temperature development during the biodrying process. The vent gas contained 15–20% oxygen and non-detectable methane, evidencing sufficient air supply. The total heat development was independent of aeration pattern; therefore, biodrying was unaffected by excess air supply at a 95% confidence level. The highest weight loss and moisture content reduction were 25% and 66%, respectively. The optimal aeration was continuous mode with non-excessive aeration, increasing the lower heating value from 2,884.0 to 4,938.0 kCal/kg, and reducing the moisture content from 48.5% to 22.2%. RDF quality can be improved 1.7 times to meet Thailand’s standards within a short biodrying period of 7 days using homogeneous temperature distribution operated under continuous aeratio