NR 110.26(3)(a)(a) Flow measurement. Devices for measuring flow to and from sludge digestion facilities shall be provided.
NR 110.26(3)(b)(b) Ventilation. All enclosures which are connected with sludge digestors, or which contain sludge or gas piping or equipment shall be provided with forced ventilation in accordance with s. NR 110.14 (3) (b). The piping gallery for digesters may not be connected to other passages unless a tightly fitting self-closing door is provided at connecting passageways.
NR 110.26(3)(c)(c) Safety. Nonsparking tools, rubber soled shoes, safety harness, gas detectors for inflammable and toxic gases and at least 2 self-contained respiratory units should be provided for emergency use whenever inflammable and toxic gases may be present.
NR 110.26(3)(d)(d) Supernatant withdrawal. Sludge thickeners and aerobic digestors shall be designed for effective separation and withdrawal of supernatant and for effective collection and removal of scum and grease.
NR 110.26(3)(e)(e) Sampling.
NR 110.26(3)(e)1.1. Provisions shall be made for sampling at each supernatant draw-off level and for collecting sludge samples for analysis. Sampling pipes shall be at least 4 centimeters (11/2 inches) in diameter and shall terminate in a suitably-sized sink or basin.
NR 110.26(3)(e)2.2. Unless sampling facilities are otherwise provided, quick-closing sampling valves shall be installed at the sludge pumps. The size of valve and piping shall be at least 4 centimeters (11/2 inches).
NR 110.26(3)(f)(f) Chemical handling. Chemical handling facilities shall meet the provisions of s. NR 110.22.
NR 110.26(4)(4)Sludge pumps and piping.
NR 110.26(4)(a)(a) Sludge pumps.
NR 110.26(4)(a)1.1. Sludge pumping systems shall be designed to handle the expected range of sludge flows.
NR 110.26(4)(a)2.2. Multiple pumps shall be provided.
NR 110.26(4)(a)3.3. Pumps with demonstrated solids handling capability shall be provided for handling raw and processed sludge.
NR 110.26(4)(a)4.4. A minimum positive head of 60 centimeters (2 feet) shall be provided at the suction side of centrifugal-type pumps and is desirable for all types of sludge pumps. Maximum suction lifts may not exceed 3.0 meters (10 feet) for plunger pumps.
NR 110.26(4)(b)(b) Sludge piping.
NR 110.26(4)(b)1.1. Sludge withdrawal piping shall have a minimum diameter of 20 centimeters (8 inches) for gravity withdrawal and 15 centimeters (6 inches) for pump suction and discharge lines. The department may approve the use of glass lined pipe which is at least 10 centimeters (4 inches) in diameter. Where withdrawal is by gravity, the available head on the discharge pipe shall be sufficient to maintain a minimum velocity of 90 centimeters (3 feet) per second.
NR 110.26(4)(b)2.2. Gravity piping shall be laid on uniform grade and alignment. The slope on gravity discharge piping may not be less than 3%.
NR 110.26(4)(b)3.3. Provisions shall be made for draining, flushing and cleaning sludge piping.
NR 110.26(4)(b)4.4. Air relief valves shall be provided at high points in pressure sludge lines.
NR 110.26(4)(b)5.5. Special consideration shall be given to the corrosion resistance and continuing stability of pipes and supports located inside the digestion tank.
NR 110.26(5)(5)Anaerobic digestion.
NR 110.26(5)(a)(a) General.
NR 110.26(5)(a)1.1. Anaerobic digesters which will also serve as supernatant separation tanks shall have a minimum side water depth of 6 meters (20 feet).
NR 110.26(5)(a)2.2. Multiple sludge inlets and draw-offs shall be provided. Multiple recirculation suction and discharge points to facilitate flexible operations and effective mixing of the digester contents shall be provided unless adequate mixing facilities are provided within the digester. One sludge inlet shall discharge above the liquid level and be located at approximately the center of the tank to assist in scum breakup. Raw sludge inlet discharge points shall be so located as to minimize short circuiting to the supernatant draw-off. Sludge withdrawal for disposal shall be from the bottom of the tank. The pipe shall be interconnected with the recirculation piping to increase flexibility in mixing tank contents.
NR 110.26(5)(b)(b) Tank capacity.
NR 110.26(5)(b)1.1. The total digestion tank capacity shall be calculated based upon the factors indicated in sub. (1). If such calculations are not done, the following minimum requirements shall be met:
NR 110.26(5)(b)1.a.a. A minimum detention time of 15 days at design flows shall be provided;
NR 110.26(5)(b)1.b.b. Completely mixed digestion systems shall provide for intimate and effective mixing to prevent stratification and to assure homogeneity of digester content. The maximum system loading shall be 1.28 kilograms per cubic meter per day (80 pounds of volatile solids per 1,000 cubic feet of volume per day) in the digester;
NR 110.26(5)(b)1.c.c. The maximum system loading for moderately mixed digestion systems in which mixing is accomplished only by circulating sludge through an external heat exchanger shall be 0.64 kilograms per cubic meter per day (40 pounds of volatile solids per 1,000 cubic feet of volume per day) in the digester; and