Biocide Residual Levels. Biocide residual levels shall be controlled in the effluents discharged to all surface waters of this State. Use Designations III and III-P. Except as provided in §B(2) of this regulation, the Department may not issue a permit allowing the use of chlorine or chlorine-containing compounds in the treatment of wastewaters discharging to Use III and Use III-P waters. Chlorine or chlorine-containing compounds may be used in the treatment of wastewaters discharged to Use III and Use III-P waters if the treatment includes dechlorination to a level set by the Department, and if the sewage treatment facility: Discharges an amount of treated sewage that is less than 1 percent of the 7-day, 10-year low flow of the receiving stream; or Was in existence on July 1, 1981, is owned or operated by a local subdivision, is required to convert from the use of chlorination to another system in order to be permitted under this regulation, and matching federal funds are not available to make the conversion. When an effluent discharged to a Use III or Use III-P water contains chlorine or chlorine-containing compounds which did not originate in the treatment of wastewater, the Department shall require dechlorination, where appropriate, to a level established under §D of this regulation. All Other Water Use Designations. A person may not discharge any chlorine or chlorine products into Use I, I-P, II, IV, or IV-P waters of this State in excess of the limits set forth below: For steam electric power stations using once-through cooling water from plants with total rated generating capacity of 25 or more megawatts, the limit shall be 0.2 milligram/liter daily maximum of total residual chlorine as determined using the amperometric titration method; For steam electric power stations using once-through cooling water from plants with total rated generating capacity of less than 25 megawatts, the limit shall be 0.2 milligram/liter monthly average and 0.5 milligram/liter daily maximum of free available chlorine as determined using the amperometric titration method; The limit for cooling tower blowdown from steam electric generating plants shall be 0.2 milligram/liter monthly average and 0.5 milligram/liter daily maximum of free available chlorine as determined using the amperometric titration method; For any other discharge category for which the EPA has published effluent limitation guidelines, the limit shall be the limits specified in the published guidelines; For all other dischargers, including sewage treatment works, the limit shall be the nondetectable level. Nondetectable Level. The nondetectable level shall be less than 0.1 milligram/liter as determined using either the DPD titrimetric or colorimetric method or an alternative method approved by the Department. Natural Constituents. The Department may make an exception to the requirements of this regulation if the chlorine or chlorine products are natural constituents of the intake water. Dechlorination. Dechlorination may be accomplished by: Chemical addition; Absorption onto activated carbon; Control of discharge rates or holding of the effluent so that chlorine residuals are reduced to the nondetectable level; or Any other method approved in advance by the Department.