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r~(- "''";.;. OPERATION AND MAINTENANCE "3') stop leakage, A worn shaft coupling in the No, 1 flocculator was repaired, The sump in the lower sludge basin was rebuilt to elimi- nate plugging of the sludge line and to permit the line to carry the full load when both sludge pumps are in operation, During the 6-day Rhutdown in March, the first opportunity presented itself for detailed inspection of many parts of the plant which were in- accessible during operation when all the channels were full of water, The main influent and effluent channels were cleaned of accumulated sludge, The holes in the carbon dioxide diffusers in the zeolite influent channel were reamed. All the valves in the filter influent and effluent channels and in the zeolite influent channel were inspected. In general, the facilities were found to be in excel- lent condition after eight years of continuous operation, While the flocculator and clarifier basins were out of service for the winter cleaning and maintenance operations, work on the center well and seal of No, 2 clarifier was completed, The rubber seal was reinforced with a metal band so that it would not suck up into the center well. Extension arms and probing tips were attached to both ends of the scraper. Similar alterations in No. 1 clarifier, completed during the preceding fiscal year, indicated the necessity of this change. Intermittent use of alum as a coagulant had resulted in the accu- mulation of a gelatinous precipitate of aluminum hydroxide in the gravel underbed of the zeolite softeners. The effect of this material was to cement the gravel with the result that the incoming water and regenerating brine channeled through the softener units, The cemented gravel underbeds were removed and new gravel was in- stalled in all the units. When the zeolite was replaced, the defi- ciency in volume of some units was made up with newly purchased siliceous zeolite, Unit No, 12 was held empty until the shipment of high-capacity resinous exchange material was received. This was the first unit in the plant to utilize an exchange material other than synthetic siliceous zeolite. The operation of this resinous ex- changer from the time of installation until the end of the fiscal year confirmed all the promising reRults obtained in earlier pilot plant tests. The use of chlorine-activated silica instead of alum as an aid to coagulation during the lime softening step in plant operation was started, and the results proved very satisfactory. Filter runs were improved and savings in chemical costs were effected through this change.