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Effect of Potassium Inhibition on the Thermophilic Anaerobic Digestion of Swine Waste
Author(s) -
Chen Ye,
Cheng Jay J.
Publication year - 2007
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143007x156853
Subject(s) - potassium , chemistry , acclimatization , chemical oxygen demand , anaerobic exercise , anaerobic digestion , food science , hydraulic retention time , thermophile , biochemistry , methane , biology , wastewater , botany , environmental engineering , enzyme , physiology , organic chemistry , engineering
The inhibition effects of high potassium concentration on thermophilic anaerobic digestion of swine waste were studied. A continuous stirred tank reactor (CSTR), operated at a hydraulic retention time of 10 days and chemical oxygen demand loading of 7.2 to 7.5 g/L/d, was used to digest swine waste and cultivate thermophilic anaerobic microorganisms. To evaluate the toxicity of potassium, batch inhibition tests were also conducted. Without acclimation to potassium, the inhibition threshold beyond which methane production decreased significantly was 3 g K + /L. Volatile fatty acids accumulation was observed during the decline of methane production. Propionic acid was the dominant fatty acid, indicating that propionic acid utilizers were more sensitive to potassium inhibition than acetoclastic methanogens. To test the effect of acclimation on potassium inhibition, the potassium concentration in the CSTR was increased to 6 and 9 g K + /L. Acclimation to 6 g K + /L increased the tolerance of anaerobic inocula to potassium inhibition without significantly reducing the methanogenic activity. The inhibition threshold was increased from 3 g K + /L for unacclimated inocula, to 6 g K + /L for inocula acclimated to 6 g/L of potassium. Acclimation of inocula to 9 g/L potassium further increased the inhibition threshold to 7.5 g K + /L. However, the overall methanogenic activity in the last case was lower than that of unacclimated and 6 g K + /L acclimated inocula.