Passaic Valley: Dependable Valmet TS key to cutting $1.2 million in costs
The Passaic Valley Sewerage Commission (PVSC) plant processes 14.5 m3 (330 mgd) of sewage and 3.4 ML/d (900,000 gpd) of out-of-district liquid waste delivered by trucks and barges. The various sludge types, mixing ratios and seasonal fluctuations disturbed the centrifuge feed concentrations.
|Location||Passaic Valley Sewerage Commission (PVSC), New Jersey, USA|
|Customer Challenge||The customer says that the measurements of solids in the influent and effluent of a sludge or biosolids process are critical, as the associated costs are as much as 50% of the entire cost of operation. To reduce those costs a dependable online measurement was needed, since four-hour manual tests were not suitable for real-time control and changes in feed solids could result in over-thickening and clogging. Existing optical instruments were not trustworthy and were never used for control.|
|Solution||The Valmet Total Solids Measurement (Valmet TS) was tested on a single centrifuge where the instrument readings of the inlet solids correlated almost perfectly to the laboratory tests. There was an initial problem with the centrifuge discharge measurement until Valmet pointed out that the line pressure should be increased to collapse air bubbles. After that, the correlation was excellent. A control test demonstrated improved stability in the centrifuge outlet solids. Then, all four centrifuges were equipped with Valmet TS, measuring the feed and discharge solids. As a service advantage, PVSC points out that the instruments have no moving parts, so the maintenance is minimal.|
|Results||In the October 2014 issue of Water Environment & Technology (WE&T) Magazine the article entitled “Once I was blind, but now I can see” co-authors from PVSC report that automatic centrifuge adjustments based on changing feed solids measured by Valmet TS has reduced the sludge volume by an average of 9%. The article concludes that the reduction in flow will save PVSC $1.2 million/yr in both in both energy and chemical costs.|