The Zootechnical Anaerobic Supernatants: Nutrient Removal by a Biological Advanced Process

This paper deals with the evaluation of total nitrogen (TN) removal from zootechnical wastes in a pilot scale reactor, treating digested supernatants by biological way. The high performances in terms of total nitrogen removal by nitrites, greater than 95%, enabled to design a medium scale treatment platform, by combining the anaerobic digestion (AD) and dewatering (DW) units with the alternate cycles (AC) biological process for pig and cattle supernatants. Theoretical mass balances carried out on maximum loading conditions allowed to define an optimal process chain and its sizing. Influent and effluent main parameters were determined for each operation unit, defining a final TN value for pig slurry equal to 14.1 g d(-1) head(-1) in the dewatered amount and 12.3 g d(-1) head(-1) from the AC reactor, besides an inner TN load of 49.6 g d(-1) head(-1). Concerning the cattle slurry treatment, the DW process gained a TN removal of 74%, allowing the AC process to remove the remaining amount of TN of about 30.1 g d(-1) head(-1). An evaluation of the reliability of a fermentation process to support the anoxic phase of the biological process was further investigated.