Section Env-Wq 716.08 - Aerobic Sludge Digestion(a) Aerobic sludge digestion shall be accomplished in a tank or tanks designed to provide effective air mixing, reduction of the organic matter, and sludge concentration under controlled conditions.(b) Tank capacities shall be based on the quantity of sludge produced and sludge characteristics including concentration and aeration time.(c) Volatile solids loading shall not exceed 300 pounds per 1,000 cubic feet of volume per day in the digestion units.(d) A minimum of 15 days detention shall be provided for waste activated sludge.(e) A minimum of 20 days detention shall be provided for primary sludge or any combination of waste activated sludge and primary sludge.(f) Duplicate tanks shall be provided unless an alternative method of solids handling or storage has been provided for use when a single digestion tank is not in service.(g) Multiple tanks shall be designed to operate either in series or in parallel.(h) The minimum quantity of oxygen provided shall be:(1) Based on 2.1 pounds of oxygen per pound of volatile solids destroyed for open tank systems; or(2) Based on 1.5 pounds of oxygen per pound of volatile solids destroyed for thermophilic systems.(i) A minimum mixing requirement of 30 cubic feet of air per minute per 1,000 cubic feet of tank volume shall be provided.(j) Facilities shall be provided for effective scum and grease removal.(k) Impact of supernatant on the wastewater treatment process shall be included in the basis of design.(l) Foam spray water piping and nozzles or other mechanical foam control devices shall be provided.(m) An unvalved emergency overflow shall be provided that will convey digester overflow to the WWTP headworks, the aeration process, or to another liquid sludge storage facility and that has an alarm for high level conditions.(n) The capacity of the blowers or air compressors shall be based on the site pressure altitude, corrected to 100°F, equivalent to 38°C, at 85% relative humidity. By controlling the rate of air delivery, the drive motor shall not be overloaded at full speed with site pressure altitude corrected to -22°F, equivalent to -30°C.N.H. Code Admin. R. Env-Wq 716.08
Adopted byVolume XXXIV Number 46, Filed November 13, 2014, Proposed by #10693, Effective 10/15/2014, Expires10/15/2024.