This amendment approves the use of three additional test procedures at Part 136 for the determination of Total Kjeldahl Nitrogen (TKN) in wastewater. Use of approved test procedures is required whenever the waste constituent specified is required to be measured for: an NPDES permit application; discharge monitoring reports; state certification; and other requests from the permitting authority for quantitative or qualitative effluent data. Use of approved test procedures is also required for the expression of pollutant amounts, characteristics, or properties in effluent limitations guidelines and standards of performance and pretreatment standards, unless otherwise specifically noted or defined.