Sec. 861.10. Effective disinfection

Effective disinfection is defined as the destruction of pathogenic organisms. Since isolation of pathogenic organisms in water is not routine, the test for the fecal coliform group of organisms will be used as an indicator.

(a) Coliform requirement.

Effective disinfection means the treatment of wastes such that the number of organisms of the fecal coliform group remaining after treatment does not exceed:

(1) 200 per 100 milliliters as a geometric average;

(2) 1,000 per 100 milliliters in more than 10 percent of the samples taken over a period of 30 consecutive days.

(b) Chlorination.

(1) Chlorination facilities shall be designed to obtain a minimum contact time of 15 minutes at peak hourly flow.

(2) After the required contact time, maintenance of a free chlorine residual of 1.0 milligram per liter at all times, as determined by the orthotolidine-arsenite (OTA) test, will be considered satisfactory if the effluent is found to meet the coliform requirements of this section.

(c) Other methods, other tests.

Other methods of achieving effective disinfection and other tests which satisfactorily demonstrate that effective disinfection has been achieved may be approved by the commission.