Cause of Gordonia amarae-like Foaming in an Incompletely Nitrifying Plant: 3.5 Year Study

Author： Asvapathanagul Pitiporn Huang Zhonghua Gedalanga Phillip B Wallace Tracy Pullen Jim Olson Betty H.

E-ISSN： 1938-6478|2012|12|4323-4331

ISSN： 1938-6478

Source： Proceedings of the Water Environment Federation, Vol.2012, Iss.12, 2012-01, pp. : 4323-4331

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Abstract

The first foaming incident at Chiquita Water Reclamation Plant (CWRP) was observed in spring 2009 and foaming episodes have reoccurred several times. The foaming incidents were not restricted by temperature (22 to 29C). Hence, foams were detected in all seasons at this study site. Also, dissolved oxygen concentrations (DO) and solids retention time (SRT), two major plant operational parameters, had no relationship with the foaming incidents. However, low biochemical oxygen demand (BOD) in primary effluent (< 100 mg/L) and low food to mass ratios (F/M ratio) were found as initiating factors of Gordonia amarae-like's growth. Yet, the G. amarae-like cell concentrations studied between 2008-2009 and in 2011, did not show strong correlations with BOD concentrations in primary effluent nor F/M ratios over the entire periods. When the BOD concentrations in primary effluent increased or returned to the average value the day after a decrease, G. amarae-like cell concentrations continued to increase. Depending on time of year, foams occurred between 2 to 8 weeks after the drop in BOD and caused solids separation problems in activated sludge. Monitoring substrate concentration in primary effluent is crucial in order to give a prewarning signal of when monitoring for G. amarae-like bacteria increases is not possible and will allow plant operators to take early preventative action before a full foaming episode occurs.