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Bioflocculating high-rate algal ponds: Control and implementation of an innovative wastewater treatment technology

Thesis/Dissertation ·
OSTI ID:5477293
High Rate Algal Ponds (HRPs) are multi-channel racetrack designs 0.2-0.5 meters deep, with pump or paddlewheel mixing, operated at 2-10 days detention time. HRPs produce higher algal concentrations (200-300 mg/L) than conventional oxidation ponds, requiring effluent algal removal to meet discharge limits. This study investigated the long-term performance of bioflocculation and sedimentation for HRP algal removal. Thirteen experiments were conducted between April 1980 and November 1982 using two 0.1 ha paddlewheel mixed HRPs at the University of California at Berkeley's Sanitary Engineering and Environmental Health Research Laboratory. Most experiments were conducted at 35 cm depth, with hydraulic loading varied seasonally to maintain settleability in response to changing insolation. Continuous 12 cm/sec paddlewheel mixing with consistent primary effluent hydraulic loading (4-11 cm/day) and sunlight loading (30-60 Kcal/L) were essential for maintaining high settleability. Bioflocculation and increased settleability were able to be induced in non-settleable ponds within several days to a few weeks after 12 cm/sec continuous paddlewheel mixing was started. Variable hydraulic loading temporarily decreases HRP settleability. Mixed HRPs achieved over 90% 24 hour TSS removals (11 mg/L) during 83 weeks of stable operation versus less than 50% (77 mg/L) for unmixed HRPS. Settling column removals reached 48% in 30 minutes (60 cm/hr) and 69% in 120 minutes under stable operational conditions. Algal morphology and settleability varied with operational and climatic conditions, with colonial Micractinium and Scenedesmus dominant. Unmixed HRPs produced minimally settleable colonies.
Research Organization:
California Univ., Berkeley, CA (United States)
OSTI ID:
5477293
Country of Publication:
United States
Language:
English