If any of these compounds are added to the wastewater stream, a small percentage will settle out with the suspended solids and potentially contaminate the sludge cake. The problem with discharging the above substances is that secondary wastewater treatment typically does not remove them. Therefore, CMSA has to take an interactive regulatory position with the local businesses to educate them on the topic, and prohibit the discharge of those compounds to the sanitary sewer. The IW staff has samples of the sludge sent to Sequoia Analytical labs semi-annually for testing to satisfy the Redwood Landfill requirements. If a contaminant value exceeds the preset limit, IW determines which local business may use a chemical compound or process that contains the subject contaminant.
Immediate investigation follows.
A schematic of the sludge production process is shown on Figure 1. A quick examination of this diagram shows the many pipelines, valves, pumps, and systems associated with the production, removal, and transport of the various sludges. The CMSA operations department monitors and controls the sludge handling systems. The processes that operations directly controls is the digester feed rates and the dewatering centrifuge operation. Both of these processes directly effect the quality and percent solids of the sludge produced.