An investigation of the fate and behaviour of a mixture of WO_3 and TiO_2 nanoparticles in a wastewater treatment plant

The fate and behaviour of WO_3 and TiO_2 mixture were investigated following the Organisation for Economic Co-operation and Development 303 A guidelines. The nanoparticles were found not to influence the chemical oxygen demand removal efficiency which was maintained 80%hence the activated sludge process was on affected. The nanoparticles were eliminated from the wastewater with a greater percentage of 99.8% for TiO_2 and 95.5% for WO_3 found in the sludge.The activated sludge process also had no effect of the polymorphs of the nanoparticles as X-ray diffraction revealed presence of monoclinic WO_3 and anatase TiO_2 which were spiked into the influent. The nanoparticles were mainly removed by bio-adsorption on the activated sludge surface. The total plate count revealed that the bacterial colonies present in the control and the test units were comparable during the gradual introduction of nanoparticles in the chambers.The biomass was 0.75 MLVSS/MLSS(mixed liquor volatile suspended solids/mixed liquor suspended solids) in both the aeration vessels thus a greater proportion of the sludge were the microorganisms. A greater percentage of the Ti and W found in the effluent was mainly due to the nanoparticles adsorbed on the suspended solids with only 3.6% Ti and 28.6% W due to dissolution of nanoparticles.     

Implementing separate waste collection and mechanical biological waste treatment in South Africa: A comparison with Austria and England

The degradation of organic compounds found in municipal solid waste (MSW) under the anaerobic landfill conditions produces gas and liquid emissions that can protract well into the landfill after-care period. The European Landfill Directives regulate the amount and nature of the organic compounds disposed into landfills. In South Africa and other developing countries, MSW is still landfilled without any kind of pre-treatment. This paper presents a pilot project of mechanical biological waste treatment (MBWT) in South Africa implemented at municipal level in the city of Durban using passively aerated open windrows. Based on case studies from Austria, England and South Africa, a waste minimisation model which can facilitate full-scale implementation of MBWT in developing countries is presented. MSW was treated in open windrows for 8 weeks. Composting temperature reached a maximum of 65 °C in less than 10 days. The results of eluate tests on waste samples from the windrows at the end of composting show a reduction of BOD₅ and BOD₅/COD ratios equal to 35.7% and 16.7%, respectively. The percent waste composition of the treated MSW was 28.3% putrescibles, 17.4% garden refuse, 13.3% plastic, 12.4% fabrics, 12% paper and other elements. The waste composition shows that more than 40% of un-treated organic material and also more than 40% non-biodegradable and recyclable materials are still landfilled without any form of biological treatment or resource recovery. A simple wet and dry waste collection model can promote recycling, treatment of biological waste before landfilling, resource recovery, labour intensive jobs and hence sustainable landfilling in the South African scenario as well as in similar developing countries.     

Energetic and exergetic performance comparison of three solar cookers for developing countries

Environment, Development and Sustainability - Three different domestic solar cookers are compared experimentally during water heating experiments using different loads. The solar cookers...