The US Clean Water Act and the application of microbiotests to demonstratecompliance

Narrative criteria of the U.S. Clean Water Act (e.g., no toxics discharged in toxic amounts) are the driving forces behind the use of microbiotests fo r the wastewater discharger to demonstrate compliance. Water quality-based permit limits rely on numeric criteria to protect certain in-stream designa ted uses. Although the values are chemical specific, they are based upon th e results of certain microbiotests as well. Site-specific modifications of these chemical-specific criteria may be developed using yet other microbiot ests. The resultant modifications often yield more realistic, yet environme ntally sound permit limits. The latest challenge to both the regulatory and regulated communities will be the application of total maximum daily loads (TMDL). The TMDL will be developed for any water body quantified as impair ed. A TMDL will be developed for any individual standard (and/or parameter of concern) deemed in exceedance for a given water body segment. Once cause and source for impairment are determined, allocations will be made between point sources and nonpoint sources. The biggest challenge to this watershe d approach will be the "selling" of the TMDL to the communities allocated l oadings and the subsequent enforcement, (C) 2000 by John Wiley & Sons, Inc.