Platte River State Fish Hatchery Effluent Management Improvements: 2009-2010

Platte River State Fish Hatchery (PRSFH) serves as the primary Pacific salmon hatchery for the Michigan DNR.  A major renovation of the outdoor rearing area was completed in 2004.  The primary focus of the renovation was to improve effluent management.  PRSFH is limited to twelve month net total phosphorus loading of 175 pounds and a rolling three month loading of 55 pounds.  The twelve month loading in 2008 was in excess of 174 pounds.  During calendar year 2009, the twelve month phosphorus loading was 244.6 pounds.  The three month limit was also violated on multiple occasions, resulting in $118,000 in penalty fines.

 Waste water treatment plant operations experts were consulted regarding possible solutions.  Multiple steps, both structural and operational, were taken to deal with the effluent issues.  The pumping frequency of the clarifier was decreased and the duration of each pumping cycle shortened.  Disc filter rotation speeds were modified to reduce bailing of process water and decrease flow to the clarifier.  The sludge tank overflow was re-plumbed so it flowed back to the clarifier rather than to the settling pond.  A ferric chloride delivery system was put in place to flocculate phosphorus in the clarifier.  The five acre settling pond was dredged, returning it to an efficient operating depth. 

 The twelve month net discharge for 2010 fell to 80.2 pounds and to only 47.4 pounds in 2011.  In September 2010, the first ever zero net phosphorus discharge was reported for PRSFH.  The cumulative net TP loading for 2012 was only 32.05 lbs., so it appears that the effect of the improvements is real.  While the shotgun approach of implementing all of the changes precludes definitive determination of which changes had the greatest impact, it is believed that adding the ferric chloride system, dredging the settling pond and replumbing the sludge tank overflow provided the most benefit.