Hydrolysis of organic wastewater particles in laboratory scale and pilot scale biofilm reactors under anoxic and aerobic conditions

Hydrolysis and degradation of particulate organic matter has been isolated and investigated in laboratory scale and pilot scale biofilters. Wastewater was supplied to biofilm reactors in order to accumulate particulates from wastewater in the filter. When synthetic wastewater with no organic matter was supplied to the reactors, hydrolysis of the particulates was the only p rocess occurring. Results from the laboratory scale experiments under aerob ic conditions with pre-settled wastewater show that the initial removal rat e is high: r(V, O2) = 2.1 kg O-2/(m(3) d) though fast declining towards a m uch slower rate. A mass balance of carbon (TOC/TIC) shows that only 10% of the accumulated TOC was transformed to TIC during the 12 hour long experime nt. The pilot scale hydrolysis experiment was performed in a new type of bi ofilm reactor - the B2A(R) biofilter that is characterised by a series of d ecreasing sized granular media (80-2.5 mm). When hydrolysis experiments wer e performed on the anoxic pilot biofilter with pre-screened wastewater part iculates as carbon source, a rapid (r(V, NO3)=0.7 kg NO3-N/(m(3) d)) and a slowler (r(V, NO3) = 0.3 kg NO3-N/(m(3) d)) removal rate were observed at a n oxygen concentration of 3.5 mg O-2/l. It was found that the pilot biofilt er could retain significant amounts of particulate organic matter, reducing the porosity of the filter media of an average from 0.35 to 0.11. A mass b alance of carbon shows that up to 40% of the total incoming TOC accumulates in the filter at high flow rates. Only up to 15% of the accumulated TOC wa s transformed to TIC during the 24 hour long experiment. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.