A new ceramic membrane has been designed by NGK Insulators Ltd., Japan, to compete in the drinking water treatment market. The IWW Water Centre, Germany, investigated the operational performance and economical feasibility of this ceramic membrane in a one year pilot study of direct river water treatment with the hybrid process of coagulation and microfiltration. The aim of this study was to investigate flux, recovery, and DOC retention performance and to determine optimum operating conditions of NGK's ceramic membrane filtration system with special regards to economical aspects. Temporarily, the performance of the ceramic membrane was challenged under adverse conditions. During pilot plant operation river water with turbidities between 3 and 100 FNU was treated. Membrane flux was increased stepwise from 80–300 l/m2h resulting in recoveries between 95.9 and 98.9%. A DOC removal between about 20–35% was achieved. The pilot study and the subsequent economical evaluation showed the potential to provide a reliable and cost competitive process option for water treatment. The robustness of the ceramic membrane filtration process makes it attractive for a broad range of water treatment applications and, due to low maintenance requirements, also suitable for drinking water treatment in developing countries.
Producing drinking water from raw waters like river bank filtrate nowadays requires the safe removal of ever new emerging organic substances. At present, in Germany perfluorinated organic compounds are heavily discussed. When it comes to trace organics removal, reverse osmosis (RO) and nanofiltration (NF) are alternatives to conventional bank filtrate treatment technologies like ozonation and activated carbon adsorption. However, the trace organics removal capabilities of dense membranes are still under investigation. Questions about concentrate disposal strategies are still open. The paper presents results from lab-scale and pilot studies which were conducted for the project planning of a 1,100 m3/h NF plant treating river Rhine bank filtrate. Membranes from loose NF to dense RO were investigated spiking the raw waters with trace organic substances which usually pass the soil passage and to some extent even the conventional treatment process. The results showed high retention capabilities of the more dense membranes, even under ageing conditions.
Due to water scarcity and water pollution, the importance of water reuse is increasing more and more. As part of a German research programme on water reuse, the effluent of a wastewater treatment plant in the coastal region of northern Germany was used to investigate the direct treatment of tertiary effluent within the project MULTI-ReUse. A modular constructed pilot system has been operated to optimize different treatment chains producing different water qualities simultaneously. The technological focus was put on membrane technologies, namely ultrafiltration (UF) and reverse osmosis (RO), and also biofiltration, adsorption and disinfection were part of the piloting. Beside the development of monitoring strategies for ensuring biological and chemical safe water qualities, the operational stability and the safe transport of water to the consumers were examined. The direct treatment of wastewater is a demanding task due to the lack of dilution and hydraulic retention time in the receiving water (environmental buffer). However, the multiple barrier approach guaranteed constant secure water. Fine adjustments of individual processes were particularly important. A stable operation of the UF could be realized in particular by using more or less intermitting inline coagulation as coating. The RO performance could be improved significantly by using monochloramine as disinfectant to minimize biofouling.
A B S T R A C TUltrafiltration (UF) has established itself as one of the key technologies in the water treatment industry over the last decade, providing superior filtrate water quality regardless of fluctuations in the feedwater quality and protecting downstream treatment steps. UF has demonstrated its advantages as seawater reverse osmosis pre-treatment for desalination application improving reverse osmosis membranes performances while extending their service life. In-depth knowledge of polymeric chemistry is mandatory for developing, manufacturing and operating new membranes. On-site evaluation of membrane performance on real water is also essential. Seawater properties can vary significantly depending on location and region. This makes it very important to pilot in order to understand the challenges and how to address them. This paper presents results obtained at different sites operating on seawater under particularly difficult conditions using inge ® Multibore ® membranes. The study describes membrane behavior when operated during algae blooms, during a monsoon period and during extreme low water temperatures (0˚C). It presents process adjustments realized to optimize the overall performance. The study shows that system optimization yields stable and long-term operation on challenging seawater without pre-treatment upstream of the UF membranes.
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