Premium
Influence of retention time and influent pH on the performance of an upflow anaerobic sludge bioreactor treating cannery waste waters
Author(s) -
Britz Trevor J.,
Trnovec Wolf,
Fourie Phillip C.
Publication year - 2000
Publication title -
international journal of food science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.831
H-Index - 96
eISSN - 1365-2621
pISSN - 0950-5423
DOI - 10.1046/j.1365-2621.2000.00332.x
Subject(s) - bioreactor , hydraulic retention time , effluent , granule (geology) , alkalinity , chemical oxygen demand , chemistry , mesophile , pulp and paper industry , anaerobic exercise , wastewater , environmental engineering , environmental science , biology , bacteria , physiology , paleontology , genetics , organic chemistry , engineering
Summary A mesophilic 50‐L upflow anaerobic sludge bed bioreactor (UASB) design was evaluated for the treatment of a sugar rich effluent from the canning industry. The UASB was inoculated with 1670 g anaerobic granules to give a granule bed height of 141 mm. After the system had stabilized the hydraulic retention time (HRT) was set at 24 h, the bioreactor substrate pH poised at 7.5 to prevent rapid acidification and the chemical oxygen demand (COD) increased to a full strength of 4000 mg.L –1 . In the first experimental study (I) the organic loading rate (OLR) was increased by shortening the HRT from 24 to 8 h to give an OLR increase from 4.0 to 9.2 kgCOD.m –3 .d –1 with an average COD removal of 81–84% and removal rate of 7.5 kgCOD.m –3 .d –1 . A HRT of 10 h was taken as the optimum operational HRT, as the recovery rate of the system at HRTs lower than 10 h were found to be longer than at longer HRTs. However, the data clearly showed that the bioreactor had not reached its optimal loading capacity, which was confirmed by the constant increase in the granule bed height. Since neutralization costs would influence the economic aspects of the process, the influence of lower pH values was investigated and the pH of the canning effluent was reduced from 7.5 to 5.0. At the lower pH, the COD removal remained fairly constant between 79 and 82%, with an alkalinity level of 700 mg.L –1 and a bioreactor effluent pH value of 6.5. It was clear from the low effluent pH that the lower end of the operational pH had been reached and further lowering of the substrate pH would lead to system failure. An increase of 144% in the granule bed height was found over the whole study period and the diameter of the granules obtained varied from below 1.0 mm to about 4.0 mm. The data from this study showed that the UASB system could successfully be used to treat canning effluents at short HRTs and without any further neutralization.