Field method for biosolids N mineralization using porous ceramic cups

A new technique was developed for field determination of N mineralization f rom biosolids, which provides a simple, inexpensive test that yields accura te results. A residuals technique was used; mineralization was defined as t he difference between the original and final mass of organic nitrogen. Bios olids were collected from a number of British Columbia wastewater treatment plants (WWTPs), placed in porous ceramic tubes and incubated under control led conditions. Variables studied included wet versus dry biosolids, applic ation rate, tube size, inoculation solution, and the effect of a soil addit ion mixed with biosolids. There was little difference in N mineralization b etween wet and dried biosolids, however variability was reduced using dried biosolids. No difference was observed using different amounts of biosolids . When dried biosolids were inoculated with supernatant obtained from a soi l and biosolids mixture, decomposition was higher than with supernatant fro m the individual mediums alone. However, mineralization was fairly close wi th all inoculates. The addition of soil had little effect on biosolids deco mposition other than resulting in a higher variability.