Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 5 - Sludge Processing and Management › Section 9VAC25-790-610 - Sludge dewatering

Current through Register Vol. 40, No. 24, July 15, 2024
A. Gravity
					 drying beds, centrifuges, and various filtration equipment can be used to
					 remove liquid from treated sewage sludge in order to reduce the amount of
					 sludge that is to be managed. Drainage from beds and centrate or filtrate from
					 dewatering units shall be returned to the sewage treatment process at
					 appropriate points preceding disinfection. These organic loads shall be
					 considered in treatment works design, and alternatives for handling these loads
					 may be considered similar to those for thickening and treatment supernatant.
					 The design of dewatering equipment used for municipal sludges containing
					 significant industrial waste shall consider the release of constituents such as
					 free metals, organic toxicants, or strong reducing/oxidizing compounds,
					 especially when thermal or chemical stabilization processes are
					 employed.
B. Capacity. Where
					 mechanical dewatering equipment is employed, at least two units shall be
					 provided unless adequate storage (separate or in-line) or an alternative means
					 of sludge handling is provided. Whenever performance reliability and sludge
					 management options are dependent on production of dewatered sludge, each of the
					 mechanical dewatering equipment provided should be designed to operate for less
					 than 60 hours during any six day period. The facility shall be able to dewater
					 in excess of 50% of the average design sludge flow with the largest unit out of
					 service. The requirements for excess capacity will depend upon the type of
					 equipment provided, peak sludge factor, and storage capability not otherwise
					 considered. All units shall have bypass capability for maintenance.
1. Where mechanical dewatering equipment will
					 not be operated on a continuous basis and the treatment works is without
					 digesters with built-in short-term storage, separate storage shall be
					 provided.
2. In-line storage of
					 stabilized or unstabilized sludge shall not interfere with the design function
					 of any of the treatment unit operations. Separate sludge storage from primary
					 digestors shall be aerated and mixed as necessary to prevent nuisance
					 conditions. The effect of storage on the sludge dewatering characteristics
					 shall be considered.
3. All
					 dewatering facilities should be properly ventilated to protect operator
					 personnel in accordance with VOSH requirements and this chapter and standards
					 contained in this chapter. The potential for odors or obnoxious gases being
					 released within or without the building and grounds and the control of such
					 should be addressed in accordance with applicable state and federal
					 requirements.
Sampling stations before and after each dewatering unit
						or any appropriate segment of the unit shall be designed to allow the periodic
						evaluation of the dewatering process.