WRRCTR No.121 Recycling of Sewage Effluent by Sugarcane Irrigation: A Posttreatment Study July 1977 to June 1978, Phase II-B (Progress Report)

Lau, L. Stephen
Young, Reginald H.F.
Loh, Philip C.
Bralts, Vincent F.
Liu, Edward K.F.
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Water Resources Research Center, University of Hawaii at Manoa
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A pilot tube farm has been installed at the Mililani Sewage Treatment Plant, O'ahu, Hawai'i, to study the necessary treatment of activated sludge effluent for drip irrigation. Four types of effluent will be processed: 100% effluent, 50% effluent diluted with 50% Waiahole Ditch water plus the 100% effluent and the 50% to 50% mix after a 3-day detention in reservoir storage. Efficacy of treatment will be determined by the rate of plugging of the holes in the drip irrigation tubes and the quality of the post-treated water. The present posttreatment system consists of two-stage pressure filtration: first through No. 3 anthracite, then through No. 11 crushed granite. Filtration rate is 0.001 36-0.002 7 m^3/s/m^2 (2-4 gpm/ft^2). The filtrate is given chemical treatment by chlorine, bromine chloride, or chlorine dioxide at a dosage equivalent to a 10 mg/l chlorine residual at the end of the drip tube line. The system and the dosages will be varied to a level that will yield least plugging. Both single-chamber and dual-chamber tubing will be tested. The tube farm is automated and is operated on a 24-hr day schedule, processing 100% effluent for 12 hr and 50 to 50% dilution for 12 hr. Backwash takes place at the end of the run. Mean values for the effluent and ditch water were respectively, suspended solids, 31 and 23 mg/l; total plate count, 3 and 30 organisms x 10^3/ml; total coliform, 34 and 970 organisms/ml; and total organic carbon, 56 and 27 mg/l. The volatile suspended solids content was 90% for the effluent but only 30% for the ditch water. A reuse bibliography has been compiled. A hydraulics test stand facility has been developed to study the effects of plugging on the hydraulics of emitter flow in drip irrigation lateral lines.
waste water treatment, Hawaii, drip irrigation, reuse
Lau LS, Young RHF, Loh PC, Bralts VF, Liu EKF. 1978. Recycling of sewage effluent by sugarcane irrigation: a posttreatment study July 1977 to June 1978, phase II-B (progress report). Honolulu (HI): Water Resources Research Center, University of Hawaii at Manoa. WRRC technical report, 121.
x + 59 pages
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