Municipal Oil Water Separator: TPH from 22,940 to 79 mg/L Through Bioremediation

Results at a glance

Metric	Before	After (day 120)
Effluent TPH	22,940 mg/L	79 mg/L (99.7% lower)
Discharge limit (100 mg/L)	Exceeded	Met and maintained
TPH at day 45	22,940 mg/L	614 mg/L
Annual pumping and disposal	$16,000	$1,200
Pumping frequency	Repeated pump-outs	Sharply reduced

The problem

A municipal oil water separator servicing 29 automotive repair garages was experiencing extreme petroleum contamination, with total petroleum hydrocarbons (TPH) measured at 22,940 mg/L, far exceeding the city discharge limit of 100 mg/L. Persistent hydrocarbon loading overwhelmed physical separation alone, forcing frequent pump-outs, high disposal costs, and ongoing regulatory non-compliance risk. The municipality needed a sustainable petroleum bioremediation solution that could reduce TPH below the 100 mg/L compliance threshold without expanding capital infrastructure or increasing pumping frequency. The project evaluated whether Petroleum Treat (PT), a high-CFU petroleum hydrocarbon degrading bacteria blend applied via continuous metering pump, could deliver active biological degradation in an automotive oil water separator under real municipal operating conditions.

Before, during, and after

Before
Prior to biological treatment, the oil water separator required repeated pumping to manage accumulated petroleum hydrocarbons in the system. TPH concentrations remained consistently elevated, averaging over 22,000 mg/L across multiple sample periods, and the municipality incurred approximately $16,000 per year in pumping and disposal costs while still struggling to maintain compliance with the 100 mg/L discharge limit. Physical separation alone could not keep pace with the hydrocarbon loading from 29 automotive repair garages, creating a persistent regulatory and financial drag on the operation.

After
Petroleum Treat (PT) Liquid was applied continuously via metering pump, enabling active biological degradation of petroleum hydrocarbons within the separator. TPH concentrations dropped from 22,940 mg/L to 614 mg/L within 45 days and were further reduced to 79 mg/L by day 120, a 99.7% total reduction that met and maintained the 100 mg/L city discharge limit. Once biological treatment stabilized, routine pumping was cut dramatically, reducing annual pumping and disposal costs from about $16,000 to $1,200 while sustaining long-term wastewater treatment performance. For municipal stormwater operators, automotive service centers, and industrial facilities running oil water separators that exceed discharge limits, this case demonstrates what continuous-feed petroleum hydrocarbon degrading bacteria can deliver on TPH reduction, regulatory compliance, and pumping cost reduction under real operating conditions.

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Product used in this trial

Petroleum Treat (PT)

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