Technical Memorandum Report No. 74
Upgrading Municipal Effluent by Pulsed-Bed Filtration: Sand Island Wastewater Treatment Plant, Oahu, Hawaii
Gordon L. Dugan
The Hydro Clear pilot plant pulsed-bed filter cell unit (4 ft2 [0.37 m3] sand surface area) was operated at the Sand Island Wastewater Treatment Plant from mid-November 1982 to the first part of June 1983. Because of the disruptive events of the influent pump malfunctioning during the first part of the study, the change of the effective sand size from 0.45 mm to 0.65 mm, and the change of the pulse-mix setting from 6 to 12, the study was segregated into five separate periods which ranged from 45 days to nearly 7 days. In terms of continuous time of operation and number of analytical results, the most representative of the five separate study periods is the first of the five periods which covered a period of 45 days and included up to 26 sets of chemical analyses. With an effective sand size of 0.45 mm and pulse-mix setting of 6 before automatic backwashing, the overall average suspended solids removal rate was 57%; the total and filterable BOD5, removal averaged respectively 41% and 42%; and the total filterable COD removal averaged respectively 38% and 27%. The backwash/processed wastewater ratio averaged 18.4%, and the hydraulic loading rate averaged 2.24 gpm/ft2 (1.522 x 10-3 m3/s/m2) .