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Technical Description Flow > 100% AHF 100% Hrs Hourly % 4 250 150 3 450 5 150 50 3 150 7 150 50 3 50 Total: 750% Equalization capacity requirement = 7.5 x 2,083 = 15,624 gallons or 31 % of average daily flow. Aeration requirements: Because flow equalization volume may be contained within the batch reactor, CFM requirements are adjusted as follows: NORMAL DEMAND 0.05 x 250 mg/L x 8.34 x 1000 ft3 = 72.23 CFM 1440 FLOW EQUALIZATION DEMAND Criteria: 50,000 gpd flow + 31% = 0.065 MGD 0.065 x250 mg/Lx 8.34 x 1000 ft3 = 94.11 CFM 1440 Comminution or screening and, where required, grit removal must precede the aeration/ equalization chamber. An emergency overflow from the aeration chamber to the buffer tank may be provided. TERTIARY FILTERS Tertiary filters are normally designed to accept a suspended solids loading of 20-30 mg/L. Occa- sional shock loads can be handled; however, the filter will not function properly at continuous suspended solids loadings of 50 mg/L or greater. Therefore, design and operation of the secon- dary plant become an important aspect in the overall efficiency of any tertiary system. If the secondary treatment plant is operated to produce an effluent with a suspended solids con- centration of less than 30 mg/L, a properly maintained, designed, and efficiently operated filter can be expected to remove 95-98.5%, or produce a resultant final effluent suspended solids con- centration of 1.5 to 5 mg/L. Bio-Pure tertiary systems have consistently produced final effluent with both BOD, and suspended solids in this range. 7H recommends for the Castello Project the use of DynaSand continuous-backwash filters. Dyna- Sand filters are approved for California Title 22 Standards for Wastewater Reclamation. When using a single pressure filter, an important design consideration is the ability of the filter to accumulate sufficient solids in the media during extended filter runs to eliminate the need for fre- quent backwashes. Frequent backwashes, which must be accomplished using a freshwater source, not only consume energy and plant operator's time but also impose additional hydraulic loading requirements on the secondary process if the backwash is directed to the aeration chamber. 15 1