Capital Region Water Dewatering Assessment
Client: Capital Region Water (for Whitman Requardt & Associates)
Project: Capital Region Water Dewatering Assessment
Project Type: Wastewater Solids Processing Support
Location: Harrisburg, Pennsylvania
To store biosolids on farms in Pennsylvania, the Pennsylvania Department of Environmental Protection (PADEP) requires that dewatered biosolids cake be at least 20% Total Solids (TS). It is critical for CRW to maintain this level of dewatering to the greatest extent possible to allow flexibility in the land application program. Additionally, improved dewatering represents substantial cost savings for CRW. Dewatering performance has been declining since the Biological Nutrient Removal (BNDR) system went online at CRW in 2015 and continues to decline.
A series of on-site assessments were performed to assess solids characteristics, as well as dewatering equipment. Four site visits assessed the following topics:
- Polymer/solids mixing
- Polymer selection and dose
- Belt Filter Press condition assessment and optimization
- Effect of pre-polymer coagulation with ferric chloride
Additionally, a review of auxiliary equipment that for aiding in dewatering was provided.
Outcomes and Benefits
Polymer dose, polymer mixing intensity, and polymer selection were assessed, with mixing intensity proving to be the most critical control point. A change in % TS of 1.7% could be observed when ideal mixing was applied, when compared to poor mixing conditions. Ferric chloride addition was assessed to determine whether it would improve dewatering performance. Addition of Ferric Chloride increased dewatering performance to above 20 % TS, while reducing polymer demand. These results demonstrate that the current equipment at CRW can provide the % TS required for farm storage, and the increase in dewatering performance could realize a savings of over $40,000/year in transportation and management costs.