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CENTRAL VALO REGIONAL WATER QUALITYONTROL BOARD IN PE TION REP RT Date: 3 June 1996 DISCHARGER: CITY OF MANTECA LOCATION &COUNTY: Manteca, San Joaquin County CONTACT(S): Jim Podesta or Warren Shannon INSPECTION DATE: 8 May 1996 INSPECTED BY: Michael H. Mosbacher ACCOMPANIED BY: Warren Shannon, Wastewater Systems Superintendent Patricia Leary, Associate WRCE,CVRWQCB OBSERVATIONS/COMMENTS: We arrived at Manteca's WQCF at approximately 9:00 A.M. Mr. Shannon accompanied us during the plant inspection. Our inspection began at the plant headworks and ended at the outfall on the San Joaquin River. The following observations were made at each of the major treatment operations: • At the headworks input flows were approximately 5.0 mgd from the City of Manteca and 0.6 mgd from the City of Lathrop. At a manhole upstream of the primary clarifiers ferrous chloride was being added to the influent stream to assist in controlling odors. • The primary clarifiers appeared almost a blackish gray in color. Mr. Shannon indicated the plant was having a problem moving into a full nitrification mode. • From the primary clarifiers we went to the top of the biotowers. The media material had a thick black gelatinous type film. Mr. Shannon indicated they had been placing RAS across the towers in a hopes of getting more organic loading to assist in the nitrification process. During the previous week foaming had been a major problem at the biotowers. • The next stop was at the aeration basins. Here we discussed what has been done in the past in an attempt to try to perform denitrification, such as flow reversal and batching without air. The color of the aeration basins was a grayish brown at the time of our inspection. Minor foaming was also occurring in the aeration tanks. • The final clarifiers had a layer of floating solids across the top, it appeared that a significant amount of suspended solids were present throughout the entire depth of the clarifiers. The clarifiers looked more like primaries rather than finals. The overflow weirs had minor amounts of build up, it did not yet appear to be causing any differential elevations or preferential flow paths from the clarifiers. • The chlorine contact chamber was not very clear and appeared to have a high amount of floating and suspended matter. Mr. Shannon indicated because of the higher suspended solids they have been required to use more than the normal amount of chlorine to meet its total coliform limits. • Manteca has constructed a new bioassay laboratory which is operational and has been certified by the Department of Health Services. REVIEWED BY: