A comprehensive study on the biological treatabilities of phenol and methanol—II the effects of temperature, pH, salinity and nutrients

Abstract

The effects of temperature, pH, salinity, and nutrients on bacterial activities were investigated and evaluated using a statistical method. The substrate utilization rate coefficient (k) decreased as pH deviated from neutral and as salinity increased, and the unfavorable pH and salinity alleviated the temperature effect on k. The modified Arrhenius equation, k T2 = k T1 θ( T2−T1) , was not effective in describing the temperature effect on k: the temperature coefficient (θ) ranged between 1.0–1.4 depending on the temperature range, pH, salinity, and substance (phenol or methanol). The endogeneous respiration activity was affected by various environmental factors such as pH, temperature, and salinity; however, the cell decay coefficient ( k d) turned out to be correlated to a single parameter, k. Thus, k d = 0.066 k 0.87 and k d = 0.0115 k 0.634, where k and k d are based on the unit of h −1, were proposed for the prediction of cell decay coefficient for phenol and methanol acclimated activated sludge, respectively. In batch treatment of 770 mg l −1 of phenol and 1000 mg l −1 of methanol as TOC, nitrogen and phosphorus did not have any recognizable effect on k, while trace elements such as Fe 2+, Mg 2+, Mn 2+, Ca 2+, and Zn 2+, etc. showed a slightly perceptible effect on it. The absence of extra-cellular nitrogen and phosphorus resulted in a greater cell yield; however, the cells in this condition decayed more rapidly than normal cells. The primary factor affecting the substrate decomposition rate in natural systems was pH: phenol decomposition resulted in a considerable decrease in pH so that the buffering capacity of the water was the most important factor, and methanol decomposition did not affect pH significantly so that the initial pH of the water was the most important factor. An initial lag phase was observed in 8 out of 115 phenol batch tests and 31 out of 66 methanol batch tests.