Water Journal : Water Journal September 2014
SEPTEMBER 2014 water 41 Conference report anionic organic flocculants, as well as an organic coagulant, were compared in conditioning of primary sludge. The research showed that dosing flocculants has an effect on biogas production, aeration requirements, COD/N ratio and, above all, dewaterability of the waste sludge. The use of cationic flocculant was found to increase gas generation and provided for improved dewaterability. Up next was Dr Istvan Licsko, Budapest University of Technology and Economics, Department of Sanitary and Environment Engineering, Hungary, who presented a paper on Dissolved-Solid Transformation of Aluminium- and Ferric-Hydroxides in Pre-treatment of Wastewaters. Traditional coagulants (aluminium- and ferric salts) typically hydrolyse rapidly and transform into poorly water-soluble positively charged aluminium- and ferric-hydroxide compounds (with sufficient alkalinity). These metal hydroxides adsorb onto the surface of colloid particles, changing their negative electric charge and decreasing their aggregative stability. Research found that aluminium and ferric hydroxides aggregate with each other, although they have positive electric charge, and this has a significant role in neutralisation of the colloids, and in the processes of floc growth. Zhiyong Zhang, State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science & Engineering, Tongji University, Shanghai, spoke on his research into treatment of papermaking wastewater by advanced oxidation processes (which included Fenton, pyrite-catalysed by hydrogen dioxide, sodium hypochlorite and ferrate oxidation). All processes generally showed reasonable COD reduction, but perhaps the pyrite-catalysed hydrogen dioxide indicated best results – at initial pH 4, pyrite dosage 1g/L, H2O2 dosage 0.15mL/L, and the oxidation reaction time 1h, COD of papermaking wastewater was reduced to 45mg/L (65 %). Hongtao Wang, Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai, spoke on Removal of TiO2 and Ag nanoparticles by clay. Research was undertaken on removal of environmental contaminants (titanium dioxide and silver) using the clay, kaolinite. Varying factors (humic acid, sodium chloride, and pH) and dosage rates were studied, with conclusions essentially showing increased aggregation with addition of kaolinite. Yi Tao, Laboratory of Microorganism Application and Risk Control of Shenzhen, Tsinghua University, China, delivered a presentation on algae removal (Synedra) using flocculant aids and pre-oxidants. Development of Synedra species in rivers and reservoirs is reported to have caused serious seasonal problems at drinking water treatment plants in China. Investigation was undertaken on removal using flocculant aids (Poly-dimethyl Diallyl Ammonium Chloride, powdered activated carbon (PAC), clay and sodium alginate) and pre-oxidants (ClO2, NaClO, and KMnO4), and using fixed coagulation dosing of 2 mg/L of polyaluminium chloride and 6 mg/L of lime solution. The results show that the addition of flocculant aids can significantly improve the removal of the algae from 50% to 95%. HCA was found to be the most effective flocculant aids for Synedra removal. Göran Bäckman, Kemira Kemi AB, Sundsvall, Sweden, spoke on Activated Sludge Optimization Using a Bioassay Measurement System (LumiKemATP). The test is used to flag toxicity presence in wastewater and also to optimise/determine the need for nutrient addition. An example of application for a pulp and paper mill's wastewater was presented, and it was shown that the data generated could be integrated with other standardised mill operating parameters. Dr Liu Jia, College of Environmental Science and Engineering, Laboratory of Pollution Control and Resource Reuse, Tongji University, spoke on her research into Synthesis of Biological Demulsifiers and Mechanism in the Breakup of Emulsions. The talk was essentially about the pre-treatment for oil recovery. Chemical demulsifiers are commonly used in China; however, demulsifying bacterial strains can achieve breakup of emulsified wastewater and enable oil recovery (enabling higher dispersion rates into the water–oil interface, and improve efficiency). Day 2 Wilbert Menkveld, Nijhuis Water Technology, The Netherlands, spoke about the proprietary Aecomix system for combined anaerobic treatment of food and beverage industry wastewater. This involves a two-stage process – mixed digester (reactor) followed by Dissolved Biogas Flotation. A case study was presented for a chocolate manufacturer, which reportedly achieved COD reduction of over 97%. The excess sludge from the aerobic system is returned to the Aecomix reactor (which is a significant advantage over high rate [UASB type] reactors). It was also claimed that the system has a 20% lower operational cost compared to a conventional DAF installation (with coagulation) followed by UASB. Valeri Razafimanantsoa, University of Stavanger, Norway, presented his research on selective size distribution of influent suspended solids on downstream biological processes. Fine The Bund is a popular spot with tourists. Some of the delegates on the grounds of Tongji University. Represented here are speakers from Germany, China, The Netherlands, Portugal, Australia and the UK.
Water Journal November 2014
Water Journal August 2014