In 2002, a large Greek Oil Depot Station's sequential batch reactor (SBR) experienced difficulties adjusting to hydraulic fluctuations in their raw wastewater, with feed varying from twice a week to once every ten days.
One stream of wastewater in the plant derives from the drainage water collected from the bottom of the collection tanks. This "dirty water" containing petroleum, benzene and jet fuel, is a portion of the ballast water used by oil tankers to travel back to the Greek Refinery in Athens, where they load their new fuel cargo for transportation back to the relevant Depot Station.
To treat this system, bacteria were required that could quickly adapt to substrate and hydraulic fluctuations. Bio-Best gents Sotiris Stassinos and Alina Simeonaki and Alken-Murray's Valerie Anne Edwards decided to test therecently improved formulation of Alken Clear-Flo 7008 (formulation improvement in the fall of 2001) in this application.
The wastewater treatment plant consists of the following:
Initial Treatment - The SBR Wastewater System
Clear-Flo 7008 was
fed in the biological tank during start up and commissioning period. After
one week of treatment, the BOD removal efficiency was greater than ninety-seven
percent and COD removal exceeded eighty percent.
Treated effluent characteristics:
Second Treatment - Odor Control in Stagnant Storage Tanks
Intermittent operation of the treatment plant caused the oily wastewater to remain stagnant in all the tanks (apart from SBR where it was constantly aerated) sometimes for as long as one to two weeks. During summer heat, this practise resulted in offensive odors traveling from the partly covered tanks in a radius of 300 meters from the plant, causing complaints from neighbors.
BIOBEST advised that small dosages of CF 7008 should be added to the odor emitting tanks and wells. After 24 hours of treatment with CF 7008, the bad odor disappeared and small air bubbles were released from the botton of the relevant tanks and wells. The client now applies preventative treatment of small doses of CF 7008 whenever water is expected to remain stagnant for more than one day. No more problems with offensive odors have been reported since treatment began.