A method for determining the effectiveness of a waste water tank deodorizer includes the steps of (i) providing a synthetic waste water media and a hydrogen sulfide generating microorganism; (ii) introducing in any order to the synthetic waste water media the hydrogen sulfide generating microorganism and a waste water tank deodorizer to be tested, and (iii) measuring the time or delay for the generation of hydrogen sulfide to occur beginning with combining of the hydrogen sulfide generating microorganism, the waste water tank deodorizer and the synthetic waste water media. Alternatively, measurement is also disclosed involving the number of bacteria present in the waste water during the test period. The invention includes a novel synthetic waste composition for use in the above method comprising at least a peptone, an animal protein extract, urea or a urea-containing compound, a metallic salt, a fiber-containing grain product and a cellulose-containing product.