High Rate Air Activated Sludge Operation at the City of Los Angeles Hyperion Wastewater Treatment Plant

Abstract

The City of Los Angeles USA Hyperion Treatment Plant (HTP) implemented high rate air activated sludge operations in November 1989. Using this process, the secondary treatment organic loading (F/M) was increased from 0.5 to 1.0 kg BOD/kg MLVSS/day and the MCRT reduced from 3.1 days to 1.5 days, thereby enabling the secondary treated flow to be increased from 150 mgd to 200mgd (6.6 to 8.8 m3/s). Excellent secondary effluent quality (BOD5 = 15 mg/l, carbonaceous BOD5 = 6 mg/l, SS = 6 mg/l) is currently obtained using rectangular secondary clarifiers operated at surface overflow rates of 1,100 gal/day/ft2 (43 m3/m2/day) and low MLSS concentrations (950 mg/l). The enhanced biological phosphorus removal that was obtained when operating at a 3 day MCRT was eliminated in the change to high rate operation and struvite (MgNH4PO4(c)) build-up in the anaerobic digesters has been eliminated. Nocardia scum formation, with its odor generating potential and other associated operating problems, has also been eliminated by high rate operation.

Navigating Wastewater Energy Recovery Strategies: A Life Cycle Comparison of Anaerobic Membrane Bioreactor and Conventional Treatment Systems with Anaerobic Digestion

“…However, limitations exist to HRAS treatment such as a poor settleability of mixed liquor to settle and low BOD 5 removal, particularly at SRTs less than 1.5 days, which can limit the use of HRAS for direct discharge. 19,20 These limitations become less of a concern when implemented in conjunction with downstream low-energy nutrient removal processes (e.g., A-stage of A/B processes). This paper compares AnMBR and HRAS+AD technologies through the application of wastewater treatment process modeling, life cycle costing (LCC), net energy balance (NEB), and life cycle assessment (LCA) methods.…”

“…Therefore, the total energy recovery possible through anaerobic digestion is maximized while aeration energy demands are minimized. However, limitations exist to HRAS treatment such as a poor settleability of mixed liquor to settle and low BOD 5 removal, particularly at SRTs less than 1.5 days, which can limit the use of HRAS for direct discharge. , These limitations become less of a concern when implemented in conjunction with downstream low-energy nutrient removal processes (e.g., A-stage of A/B processes).…”

Biological Phosphorus Removal

“…Mamais and Jenkins (1992) studied the effect of SRT on EBPR varying over 2-4 days at temperatures of 13.5-20 1C in a continuous bench-scale reaction system. Shao et al (1992) investigated phosphorus removal at Hyperion Treatment Plant, City of Los Angeles, CA, USA, with an objective of preventing the occurrence of EBPR in the plant, as it was resulting in the formation of struvite (MgNH 4 PO 4 (s)). However, when the SRT was lower than 2.9 days, the efficiency of the system depended on both SRT and temperature conditions.…”