Abstract
Wastewater discharged from vermicelli factories has a high concentration of starch and
protein, with COD and BOD ranging from 30 000 to 60 000 mg/liter and 24 000 to 44 000
mg/liter, respectively. Because of these high concentrations, the wastewater is
considered to be heavy and particulated. Wild yeasts were screened and applied to treat
the vermicelli wastewater.
Ten isolated strains having the ability of starch degradation, protein hydrolysis and lactic
acid tolerance were screened. Treatment of wastewater from a vermicelli factory, with
C:N:P ratio adjusted, using isolated yeasts in batch culture showed that two strains could
reduce soluble COD by 79–83%. When the hydraulic retention time and solid retention
time were kept at 7·14 days, using a semicontinuous
culture, the solid loading was 0·48
g COD/gMLSS per day, volumetric loading was 1·03 kg COD/m3 per day, and the COD
removal was about 92%.