ab s t r ac tThis paper discusses the use of the non-oxidative biocide 2,2-dibromo-3-nitrilopropionamide (DB-NPA) to minimize and/or eliminate problems due to biofouling accumulation and to ensure longterm performance of a RO system. DBNPA is a suitable biocide due to its compatibility with reverse osmosis (RO) membranes. Our aim is to present a better understanding of DBNPA, its rejection by common RO membrane types and the environmental chemistry concepts for residual DBNPA and its by-products in the outlet concentrate stream. The application areas covered are industrial water and off-line drinking water systems. Examples of field studies conducted on full-scale RO systems that use DBNPA will be shown. Also discussed are the data obtained from the analysis that was carried out to determine the degradation of DBNPA in the RO feed and outlet stream. The benefits of using DBNPA for biofouling prevention include reducing the required feed pressure and the cleaning frequency of the RO system. Other benefits are reduced cleaning chemical costs, reduced downtime of the plant and reduced time of the operators. This results in increased output of the plant and reduced operating expenses of the RO operation.

Sodium metabisulphite (SMBS) is the current standard preservation chemical used in RO plants during shut down. It is a cheap and efficient preservative, but its tendency to oxidize easily has several drawbacks. The use of a non-oxidizing biocide instead could solve some of the issues currently seen with the SMBS, but little has been reported about membrane compatibility and preservation efficiency in the long-term mode. Long-term membrane preservation trials have been executed with three different non-oxidizing biocides: DBNPA (2,2-dibromo-3-nitrilopropionamide), CMIT/MIT (5-chloro-2-methyl-4-isothiazolin-3-one (CMIT) and 2-methyl-4-isothiazolin-3-one (MIT), OIT (2-octyl-2H-isothiazol-3-one) as well as SMBS as the reference chemical. The suitability of these chemicals in this application was confirmed using both new Brackish Water Reverse Osmosis (BWRO) and used membranes with various membrane chemistries (Nanofiltration (NF), BWRO, Sea Water Reverse Osmosis (SWRO)). The preservation trial with new membranes confirmed the long-term stability of the product when stored in the biocide solution while the trial with used elements is closer to realistic plant conditions and validated the efficiency of the biocide against biofouling in the long-term. These results show that the biocides can be equivalent preservatives to SMBS and that the application is economically feasible. The used active concentrations for biocides are storage time and temperature dependent and this should be taken into account when first applying them in the field.

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ab s t r ac tThe DECO water treatment facility (built and operated by Evides Industriewater B.V.) is using an integrated membrane system to produce demineralised water for the production facilities of Dow Benelux B.V in Terneuzen, the Netherlands. The system consists of large-scale continuous microfi ltration (CMF) unit and two-pass reverse osmosis (RO) unit with FILMTEC TM membranes. It is the fi rst time in the Netherlands that domestic waste water is re-used in such a large scale for industrial use. This is an excellent example of a full scale process which was adjusted to preserve scarce fresh water resources in the region. The main goal-to minimize the environmental impact and to maximize water recovery through water recycling loops, thereby supporting the chemical industry movement to improve sustainability. This paper discusses the operational experience of the first 18 months operation with wastewater. The plant was started in 2000 and was originally designed to desalinate estuary water, due the lack of fresh water in the region. The water source was challenging due to high chemical and biological variability, which lead to operational diffi culties like biofouling and high maintenance costs due to corrosion. In 2006 the plant was re-engineered to treat municipal waste water originating from the nearby city of Terneuzen. Re-engineering consisted of new RO membrane design, low pressure feed pumps and process automation adjustments. The DECO plant uses fouling resistant membranes (BW30-400/34i-FR) with a thick feed spacer. The spacer reduces the fouling potential and facilitates cleaning. In addition, the plant is using frequent preventive cleanings, which is only possible with robust membranes. These actions have led to stabile operation in terms of permeate fl ow and the good quality of the produced permeate (<10 μS/cm). This case shows that operational problems caused by the biologically active wastewater can be eliminated by a good plant design (membrane selection) and good operational practices. The facility reports signifi cant savings, 20% increase in the system recovery and 50% reduction in the operational cost (OPEX) with the implementation of the waste water treated system. The savings in OPEX are mainly related to energy costs and decreased use of chemicals for water treatment. In addition, the environmental impact is reduced as the city's waste water is no longer discharged to the sea, but given another life as process water.Trademark of The Dow Chemical Company ("Dow") or an affi liated company of Dow.

The growing demand on water resources has increased the interest in wastewater reclamation for multiple end-use applications such as indirect and direct potable reuse. In these applications, the removal of organic micropollutants is of a greater concern than in conventional wastewater treatment. This article presents a collection of data of trace organic micropollutants in an urban wastewater treatment plant (WWTP) in North East Spain using reverse osmosis (RO) membrane treatment. The RO rejection values of the organic molecules studied with a wide range of solute size and hydrophobicity were determined. Several chromatographic methods monitoring different endocrine disrupting chemicals (EDCs), pharmaceuticals and personal care products (PPCPs) were used. Results indicated that secondary effluents from this Spanish WWTP contained most of the studied organic compounds indicating incomplete removal of organics in the conventional treatment of the plant. However, the rejection of most micropollutants was high for all three RO membrane types (low energy, high rejection, fouling resistant) tested. It was observed that some selected micropollutants were less efficiently removed (e.g. the small and polar and the more hydrophobic) and the molecular weight and membrane material influenced removal efficiencies.