(a) The purpose of this subchapter is to promulgate a set of effluent quality limitations for treated domestic sewage which will be required of permittees as appropriate to maintain water quality in accordance with the commission's surface water quality standards. Any incorporation of federal regulations into this chapter shall apply only to disposal of domestic sewage.
(b) Secondary treatment, with exceptions applicable to certain stabilization pond systems and other natural systems, is defined as a minimum reduction of pollutants to meet the quality specified in Figure: 30 TAC §309.1(b):
Attached Graphic
(c) Effective April 1988, all permits containing an ammonia-nitrogen effluent limit are modified to change Biochemical Oxygen Demand (BOD5 ) to carbonaceous biochemical oxygen demand (CBOD5 ).
(d) Effective January 1, 1988, any permit containing a BOD5 effluent limitation may be monitored and reported as CBOD5 as long as nitrogen is monitored and reported as ammonia-nitrogen at the same sampling frequency. If the permit authorizes a discharge to land or an evaporation pond only, ammonia-nitrogen monitoring and reporting are not required to change to CBOD5 .
(e) The state of Texas has established a state water quality management program and a continuing planning process which sets forth the strategy and procedures for accomplishing the management program's objectives. Essential elements of the program include updates of basin plans, total maximum daily loads, and wasteload evaluations by basin segments. In order to achieve compliance with water quality standards within certain segments, more stringent effluent quality limitations other than basic secondary treatment may be required to protect water quality.

Source Note: The provisions of this §309.1 adopted to be effective March 19, 1990, 15 TexReg 1160; amended to be effective October 8, 1990, 15 TexReg 5500; amended to be effective June 5, 1998, 23 TexReg 5723; amended to be effective January 9, 2020, 45 TexReg 370