Formation of a Minute Amount of Excess Sludge in the Treatment of High Strength Organic Wastewater by Thermophilic Oxic Process.

Abstract

A thermophilic oxic process was defined as the process which aerobically treats the high strength organic wastewater absorbed in the medium. Red bean processing wastewater was used in this experiment for investigating the formation of a minute amount of excess sludge affected by BOD load and temperature of the medium. The concentrations of biochemical oxygen demand (BOD) and suspended solids (SS) of the wastewater were 36, 000mg/l and 4, 200mg/l, respectively. Wastewater was absorbed by the medium such as cedar chips, resulting in the improvement of air permeability. The medium functioned to provide a habitat for thermophilic bacteria. When the BOD load was 4kg⋅m-3⋅d-1 and the added water load was 110l⋅m-3⋅d-1, organic matter was effectively decomposed and the temperature increased to higher than 50°C. Though the removal efficiency of BOD was larger than 95%, a minute amount of excess sludge was formed because most of the organic matter in wastewater was converted to carbon dioxide (CO2) in the off-gas when the temperature was higher than 50°C. The constancy of the number of the thermophilic bacteria in the reactor was also observed.