Integrated Engineers develops cost factors for determining the true costs of liquid solids separation used to clearly define the true operational costs of each wastewater treatment facility and the facility’s potential for cutting costs.
Cost Factors for Liquid/Solids Separation
Each of these points should be used to clearly define the true operational costs of each wastewater treatment facility.
1. Chemical Costs: These include all of the chemicals (acid, caustic, lime, coagulants, flocculants, dewatering aids, and others).
2. Surcharges paid to the POTW: The local wastewater facility charges for BOD, TSS and FOG usually on a monthly basis on a pound/day fee.
3. Quantity of Chemicals used onsite: The more chemicals onsite, the more chemical handling and storage. Hazardous chemicals require secondary containment for storage.
4. Dewatering Aids: The cost is the price per lb of the DE as well as the sludge it generates. Note, for every pound of DE used, it generates 3 pounds of sludge.
5. Drum and/or Tote Disposal: Some facilities are charged a disposal fee for cleaning and recycling of the drums and totes.
6. Drum/Tote Storage: Since some of these chemicals are hazardous, they need to be stored with secondary containment. Others will not. What is the storage cost to the facility?
7. Hazardous Chemicals: The alum, ferric, acid (pH lower than 5.0), caustic (pH over 10) and other are all hazardous to the employees. The facility must pay extra for workman’s Compensation and accident/injury insurances for having hazardous chemical handling onsite. What is this cost?
8. Sludge Production: What is the cost for sludge disposal? These costs need to include tipping fees as well as freight from the point of origin to the point of disposal.
9. Sludge Quality: The higher the % solids, the lower the disposal cost, as the facility is not paying for disposal of the water in the sludge.
10. Sludge Classification: The classification of the sludge can greatly affect the price of disposal. Hazardous is most expensive and requires manifests and documentation and for larger facilities, reporting as a hazardous waste generator. All sludge has a disposal cost.
11. Labor: The labor and functions performed from this labor factor need to be accounted for and added to the overall cost.
12. Labor, environmental: Include the EHS labor and costs (monthly or quarterly reporting, manifests, etc.).
13. Water Reuse: Sometimes, a facility can reuse their wastewater, savings $ on incoming water and outgoing sewer fees.
14. System Capacity: Is the current system limited in capacity? Does this limit facility production?
15. Electrical Costs: What is the cost in electricity? This is tied to the system operating time in hours/day.
16. Filtrate Quality: The chemicals added forms a floc that has a shear strength proportional to the sludge dewaterability and filtrate clarity. If additional polymers are needed this is a cost. If the filtrate is cloudy with suspended solids, this has to be retreated or adds directly to the surcharges paid.
17. Recover Oil: For oily waters, is there a cost savings to recover oil?
18. Recover Precious Metals: If the industry has precious metals (gold, platinum, silver, etc.) these can be removed and recovered.
19. Metals Removal: Tight local discharge limits can reduce wastewater throughput as well as plant production. Is this a cost factor?
As one can see, there are many aspects to determing the true costs of liquid solid separation. Overlooking any can impede a true optimization process.