Passaic Valley: Dependable Valmet TS key to cutting $1.2 million in costs
Nov 23, 2015
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.
This application results report is condensed from an article in the October, 2014 issue of Water Environment & Technology (WE&T) Magazine entitled “Once I was blind, but now I can see.”
Operating a sludge or biosolids process without knowing the percent solids in the influent and effluent is like driving a car blindfolded. This data is critical for sludge, as the associated costs for treatment are as much as 50% of the entire cost of operating a water resource and recovery operation."
PVSC staff
Summary
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.
