NR 110.16(1)(e)(e) Handling screenings. Adequate facilities must be provided for removal, handling and storage of screenings in a sanitary manner. Hand-cleaned screening facilities must include an accessible platform from which the operator may rake screenings. Suitable drainage facilities must be provided for both the platform and the storage areas. NR 110.16(2)(a)1.1. Clear spacing between bars may not be less than 2.5 centimeters (1 inch), nor more than 5 centimeters (2 inches). NR 110.16(2)(a)2.2. Bar screens must be placed on a slope of 30 to 45 degrees with the horizontal with the exception of those installed for emergency use. NR 110.16(2)(a)3.3. Approach velocities may be no less than 38 centimeters per second (1.25 feet per second) at design average flow conditions to prevent settling, and no greater than 91 centimeters per second (3 feet per second) at maximum design daily flow to prevent forcing material through the openings. NR 110.16(2)(b)1.1. Maximum clean spacing between bars may not exceed 5 centimeters (2 inches). NR 110.16(2)(b)2.2. Approach velocities may be no less than 38 centimeters per second (1.25 feet per second) at average design flow conditions to prevent settling, and no greater than 91 centimeters per second (3 feet per second) at maximum daily flow to prevent forcing material through the openings. NR 110.16(2)(b)3.3. All mechanical units which are operated by timing devices shall be provided with auxiliary controls which will set the cleaning mechanism in operation at a preset high water elevation. NR 110.16(2)(b)4.4. Automatic controls shall be supplemented by a manual override. Manual overrides shall be located in view of the equipment. NR 110.16(2)(b)5.5. Electrical fixtures and controls in screening areas where hazardous gases may accumulate shall meet the requirements of the national electrical code for class 1, group D, division 1 locations. NR 110.16(2)(c)1.1. Comminutors shall be designed to comminute the maximum design flow rate. NR 110.16(2)(c)2.2. Comminutor channels shall be designed to contain the upstream water depth associated with the head loss which occurs at maximum design flow without surcharging the incoming sewer or other treatment processes. The expected head loss shall take into account the effects of clogging during operation. NR 110.16(2)(c)4.4. A screened bypass channel shall be provided so that the comminutor may be removed from service for maintenance. NR 110.16(2)(c)5.5. Bypass channels will not be required where 2 comminutors are installed. Each comminutor shall be capable of comminuting the maximum design flow. NR 110.16(2)(c)6.6. Control switches or a disconnecting device for the comminutor shall be located in view of the comminutor. NR 110.16(2)(c)7.7. Electrical fixtures and controls in comminutors areas where hazardous gases may accumulate shall meet the requirements of the national electrical code for class 1, group D, division 1 locations. NR 110.16 HistoryHistory: Cr. Register, November, 1974, No. 227, eff. 12-1-74; r. and recr. Register, February, 1983, No. 326, eff. 3-1-83. NR 110.17(1)(1) Applicability. Grit removal facilities are recommended for all sewage plants and are required for plants receiving sewage from combined sewers or from sewer systems receiving substantial amounts of grit. NR 110.17(2)(a)(a) Location. Where practical, grit chambers should precede influent pumps. When installed, grit chambers shall precede all major treatment units. NR 110.17(2)(b)(b) Protection. All grit chambers shall be preceded by a bar rack, coarse screen or comminutor. NR 110.17(2)(c)1.1. Enclosed grit removal areas shall be ventilated. Fresh air shall be introduced continuously at a rate of 12 air changes per hour, or intermittently at a rate of 30 air changes per hour. NR 110.17(2)(c)2.2. All electrical work in enclosed grit removal areas where hazardous gases may accumulate shall meet the requirements of the national electrical code for class 1, group D, division 1 locations.