NR 811.47(7)(f)(f) Tube or plate settlers. Proposals for settler unit clarification shall include pilot plant or a full scale demonstration or both satisfactory to the department prior to the preparation of final plans and specifications for approval. Settler units consisting of variously shaped tubes or plates which are installed in multiple layers and at an angle to the flow, may be used for sedimentation, following flocculation. Tube or plate settler installations shall meet the following:

NR 811.47(7)(f)1.1. ‘Inlet and outlet considerations.’ Design the inlets and outlets to maintain velocities suitable for settling in the basin and to minimize short-circuiting.

NR 811.47(7)(f)2.2. ‘Drainage.’ Drain piping from the settler units shall be sized to facilitate a quick flush of the settler units and to prevent flooding other portions of the plant.

NR 811.47(7)(f)4.4. ‘Application rate for tubes.’ A maximum application rate of 2 gallons per minute per square foot of cross-sectional area, unless higher rates are successfully shown through pilot plant or in-plant demonstration studies and are approved by the department.

NR 811.47(7)(f)5.5. ‘Application rate for plates.’ A maximum plate loading rate of 0.5 gallons per minute per square foot, based on 80 percent of the projected horizontal plate area.

NR 811.47(7)(f)6.6. ‘Flushing lines.’ Flushing lines shall be provided to facilitate maintenance and shall be properly protected against backflow or back siphonage.

NR 811.47(7)(f)7.7. ‘Placement.’ Modules shall be placed in zones of stable hydraulic conditions and in areas nearest effluent launders for basins not completely covered by the modules.

NR 811.47 HistoryHistory: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10; CR 22-074: am. (intro.), (7) (b) 1. Register January 2024 No. 817, eff. 2-1-24.

NR 811.48(1)(a)(a) Type. The following types of chemical feed equipment may be used to feed chlorine:

NR 811.48(1)(b)(b) Capacity. The chlorinator capacity shall be such that a free chlorine dose of at least 2 mg/L can be attained when maximum flow rates coincide with anticipated maximum chlorine demands. Liquid chemical feed equipment shall be designed to operate in accordance with the requirements under s. NR 811.39 (2) (c). Solution-feed-gas-type chlorination chemical feed equipment shall be designed to operate between 10 percent and 70 percent of the rotameter capacity. This may require that 2 rotameters be provided, one for normal feed rates and one for emergency feed rates. For all chemical feed systems, the emergency feeder setting shall be designed to provide a minimum of 2 mg/L of chlorine.

NR 811.48(1)(c)(c) Standby equipment. Where chlorination is necessary for protection of the water supply, standby equipment of sufficient capacity shall be available to replace the largest unit during shut-downs. Spare parts shall be made available to replace parts subject to scaling, wear, and breakage.

NR 811.48(1)(d)(d) Automatic proportioning. Automatic proportioning chlorinators shall be required where the rate of flow of the water is not reasonably constant or where the rate of flow of the water is not manually controlled.

NR 811.48(2)(a)(a) Chlorine shall be applied at a point which will provide the maximum contact time. Provisions shall be made to minimize short-circuiting.

NR 811.48(2)(b)(b) At plants treating surface water, piping provisions shall be made for applying chlorine to the raw water, settled or clarified water, filtered water, and the plant effluent.

NR 811.48(2)(c)(c) At plants treating groundwater, provision shall be made for applying chlorine to the raw water, the clearwell inlet, and the discharge piping as applicable.

NR 811.48(2)(d)(d) At plants treating groundwater where CT is required by the department, provision shall be made for applying chlorine to the raw water, at the inlet to all CT reservoir detention basins, and the high-lift pump discharge piping as required by the department.