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New Hypothesis for Secondary Clarifier Performance Under Hydraulically Limited Conditions
Author(s) -
Narayanan B.,
Hough S.G.,
Ooten R.J.
Publication year - 2000
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143000x137185
Subject(s) - clarifier , effluent , environmental engineering , environmental science , flocculation , wastewater , sewage treatment , pulp and paper industry , engineering
A new criterion called the effluent upflow velocity (EUV) is proposed as an important parameter affecting secondary clarifier performance under hydraulically limited conditions. Defined as the upflow velocity in the effluent withdrawal zone of a secondary clarifier, the EUV is proposed as having a direct link to clarifier performance in the presence of a wide range of particle size distributions in the effluent withdrawal zone. It is hypothesized that a wide range of particle size distributions in the effluent withdrawal zone of a clarifier could result from one of two factors: poor mixed liquor flocculation characteristics or strong density currents capable of resuspending previously settled floc. Consequently, in the presence of either of these factors, the EUV would likely show the best correlation with clarifier effluent suspended solids, more so than traditional hydraulic criteria such as the surface overflow rate or weir loading rate. Results from clarifier modifications completed at the County Sanitation Districts of Orange County's Wastewater Treatment Plant No. 2 in Huntington Beach, California, are presented in support of this hypothesis.