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For over a year PWN Water Supply Company North-Holland applies UV/Hsub2/subOsub2/sub treatment(540 mJ/cmsup2/sup; 6 mg/L Hsub2/subOsub2/sub) for organic contaminant control and primary disinfection at hertreatment facility Andijk (20 MGD; 3000 msup3/sup/h) for the production of drinking water. Beforeimplementation of UV/Hsub2/subOsub2/sub, organic contaminant control was achieved by granular activatedcarbon (GAC) filtration with an empty bed contact time of 30 minutes. Primary disinfectionwas achieved by breakpoint chlorination. The original process had to be upgraded in view ofthe presence of polar compounds and pathogenic micro-organisms such as protozoa.Before full scale implementation, the UV/Hsub2/subOsub2/sub technology was investigated on batch andpilot scale in a five year research project. The impact of retrofitting the existing treatmentprocess with UV/Hsub2/subOsub2/sub was monitored on pilot scale for two years. The year before theUV/Hsub2/subOsub2/sub process became operational, monitoring results from the existing process withbreakpoint chlorination were gathered. The monitoring program was continued after the plantwas retrofitted. This program covered pesticides such as atrazine, bentazone and AMPA, thecomplexing agent EDTA, the halogenated carboxylic acid TCA, emerging substances such asNDMA, pharmaceuticals such as carbamazepine and pathogenic micro-organisms such asviruses. Comparing the lab scale and pilot plant data with the results of one year monitoringthe performance of the full scale UV/Hsub2/subOsub2/sub process, leads to the conclusion that the full scaleUV/Hsub2/subOsub2/sub process performs as expected and satisfies all quality standards.By implementation of UV/Hsub2/subOsub2/sub, the role of the existing GAC filters changed significantly. Inthe original treatment train with breakpoint chlorination, the main function of the GAC filterswas adsorption of organic micropollutants, especially THM's. After implementation ofUV/Hsub2/subOsub2/sub, the objectives of the GAC filters are to quench the residual Hsub2/subOsub2/sub, to convert theformed nitrite into nitrate and biodegradation of oxidation products, thereby obtainingbiological stable water. Parameters such as THM's, Hsub2/subOsub2/sub, nitrate and nitrite, AOC in thetreatment process have been monitored before and after the retrofitting of the facility withUV/Hsub2/subOsub2/sub. The effect of the transformation from adsorptive to biological GAC filter wasconsistent with earlier pilot results. The level of biological stability of the produced water iscomparable before and after the implementation of UV/Hsub2/subOsub2/sub. THM's adsorbed by the GACduring breakpoint chlorination desorbed over a period of about one year.The retrofitted Andijk facility with UV/Hsub2/subOsub2/sub as nonselective barrier against organic micropollutants and primary disinfection step in combination with biological GAC filters hasproven to be a robust solution for the production of safe and reliable drinking water fromsurface water. PWN has decided to implement the UV/Hsub2/subOsub2/sub process at her facility Heemskerk(40 MGD; 6000 msup3/sup/h) as well. Includes 6 references, tables, figures.

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Edition: Vol. - No. Published: 11/01/2006 Number of Pages: 15File Size: 1 file , 520 KB