Liquids Management: Wastewater Pretreatment Permit and System Design, California Jewelry Mart

The successful pretreatment system reduces California Jewelry Mart’s risk of violating its wastewater discharge permit.

Background
California Jewelry Mart (CJM) houses multiple jewelry manufacturers. It is classified as a metal finishing facility under Federal Categorical Pretreatment Standards and must comply with an industrial wastewater discharge permit with pre-treatment for cyanide and metals (silver).

Challenge
CJM had 120 days to design and install a wastewater pretreatment system because the site regulator enacted a Consent Order. CJM needed to move quickly to maintain operations, but because there are multiple tenants in a single facility, its wastewater quality and quantity varied significantly. In addition to pre-treatment for cyanide and metals, large amounts of calcium sulfate had to be allowed for, from the jewelry making process. Calcium sulfate causes maintenance problems because it accumulates on pipes and fouls them. In addition, CJM wanted to make sure the new system would fit in a basement boiler room that had restricted accessibility.

CJM chose SCS Engineers (SCS) to help overcome these challenges. To address the inconsistencies in the quality and quantity of wastewater coming from its multiple tenants, SCS performed the following services:

• Enacted a program of tenant inspections, surveillance, and training to minimize variability in cyanide and metals (silver) contaminant loading and wastewater flow rate.
• Designed a pretreatment system with maximum flexibility for changing conditions.
• Based its design criteria using worst-case water quality and flow rates.

To overcome the issues caused by high levels of calcium sulfate, SCS specified diaphragm pumps and valves and plasticized PVC piping, which resisted fouling due to the calcium sulfate. SCS designed process tanks with clean-outs for removal of accumulated calcium sulfate and designed and installed a chemical treatment system at the head of the system to remove the calcium sulfate before it could damage the remainder of the system. In addition, SCS prepared a custom design of the carbon adsorption system to minimize the impact of the calcium sulfate.

To overcome CJM’s concerns about the location restrictions of the new system, SCS delivered these improvements:

• Made the best use of space through the design of a mezzanine level for additional process tanks.
• Installed remote fill ports for treatment chemical delivery.
• Designed a modular system that could be expanded by adding more modules.
• Fabricated large equipment in place.
• Worked evenings to minimize the impact of foot and vehicle traffic on construction activities.

Outcomes and Benefits
CJM overcame the challenges within 120 days to remain in compliance with the industrial wastewater discharge permit requirements for cyanide and metals. CJM has a flexible wastewater system in a location that meets the varied demands of its multiple tenants. The successful pretreatment system significantly reduces CJM’s risk of violating its wastewater discharge permit.