ESTIMATING THE ALLOWABLE AMMONIA CONCENTRATIONS IN WASTE-WATER TREATMENT-PLANT DISCHARGE TO ENSURE PROTECTION OF AQUATIC BIOTA

Ammonia, a common constituent of wastewaters, is toxic to a wide range of aquatic organisms. Fish are the most sensitive species and cold-wa ter, oxygen-sensitive, fish such as trout are the most vulnerable. The US Environmental Protection Agency (USEPA) has developed models of fi sh-tolerance to ammonia levels. These criteria have been adopted in Au stralian Water Quality Guidelines for Fresh and Marine Waters [1]. Giv en that the toxicity of ammonia is dependent on the prevailing tempera ture and pH, allowable concentrations of ammonia in aquatic systems su ch as lakes and estuaries must take these factors into account. We des cribe a simple procedure for estimating the allowable ammonia concentr ations in discharges from wastewater treatment plants to ensure protec tion of aquatic biota. The procedure incorporates the USEPA fish-toler ance models and considers the dependency of ammonia on ambient tempera ture and pH levels and the volume of discharge and recieving waters.