Attachment 3: PWPP Process Description

Attachment 3
Wastewater Pretreatment Plant (WWPP) Chemical Treatment Process Plating Wastewater Pretreatment Plant (PWPP)
PROCESS DESCRIPTION: In the Plating Wastewater Pretreatment Plant (PWPP) plating wastewater is treated by removing the heavy metals from the process wastewater. The wastewater is collected in holding tank T-26 (equalization tank in PWPP) from the two plating operations including T-4A (surge tank in Annex Basement RM 23-2-1A). (NOTE: T-4A is the beginning of the PWPP. All equipment from T-4A is covered under this contract, including all the piping system to T-26 from the Annex building to the main building.) The wastewater is then pumped to T-4 and then pumped to an oil/water separator. The wastewater then flows into treatment tank T-1 where sodium bisulfite is added to reduce hexavalent chromium to trivalent chromium. 93% sulfuric acid is also added to T-1 to maintain a pH less than 3.0 to reduce the required residence time in T-1. The wastewater then flows to tank T-2 where the pH is adjusted with 50% sodium hydroxide. The wastewater next flows through a mellifier (clarifier) for gravity separation of precipitated solids, and the supernatant wastewater flows to a surge tank T-5. Polymer from tank T-9 is also added to the upstream of the mellifier at an in-line mixer, as needed, to assist in the separation/precipitation process. From tank T-5, the water is pumped through a filter media system to tank T-6, and then to the sewer. Water from tank T-6 is also used to back wash the filter media. The dirty backwash water is pumped to T-4, and the water is then slowly returned to tank T-1 for treatment. The sludge is pumped from the mellifier to a sludge storage and dewatering tank T-10. The sludge in T-10 is pumped to a sludge filter press where the sludge is concentrated into sludge cakes for disposal. The water, which is discharged from the press, flows to the sump beneath the filter press T-25 and is pumped back to T-2 for reprocessing. The solids from the filter press are disposed of in accordance with EPA regulations.
PROCESS OPERATION: The Contractor shall operate the PWPP with prudent engineering and operating practices. Operating the PWPP includes, but is not limited to, the following tasks:

Att. 3

(1)

The Contractor shall take readings every two (2) hours of the pumps, flows, tank levels, data set points and operating conditions from the PLC. It should be noted that in the future this may be at least partially performed by SCADA software.