ANALYSIS AND FEASIBILITY OF CHEMICAL PRODUCTS REDUCTION IN THE CLEAN IN PLACE OF ULTRAFILTRATION AS A PRE-TREATMENT TECHNOLOGY FOR REVERSE OSMOSIS DESALINATION

Abstract

The reverse osmosis seawater desalination plants open-intake requires different strategies of pre-treatment to reduce the biofouling and scaling. The UltraFiltration (UF) technology is a recent application to this process. In this work, some alternatives to chemical products reducing in chemically enhanced backwash (CEB) and clean in place (CIP) of a UF rack have been studied. Mainly the sodium hypochlorite consumption, due to its biofouling precursor effect over reverse osmosis membranes. For this purpose, the optimal filtration time has been studied, to get the highest water production prior to the CIP, as well as some modifications in the conventional CIP's, modifying the duration of the stages of the same. The results were compared with the current mode of daily operation of the CEB. The results show that a reduction of up to 60% in the amount of sodium hypochlorite per cubic meter of water produced employed in UF CEB's, mini CIP's and CIP's can be achieved. However, the consumption of the rest of chemical dosing increased notably, and therefore the operating cost of UF also increased. In addition, there was an increase of desalted water consumption to the chemical products removed, up to almost 95,84 %, in comparison with the currently operational mode of CEB. On the other hand, operating the UF plant in the manner proposed requires a automatization of the process and expert staff to programme the control. Therefore, based on the results obtained, the alternatives proposed could reduce the chemical products in use, but it is not conclusive in terms of exploitation operational costs. Key Words: Ultrafiltration, Reverse osmosis, Open-intake, Clean in place, Chemically Enhanced Backwash, chemical products reduction, biofouling, pre-treatment.