Biological Treatment of Wastewater

Brief Introduction

Anaerobic biological treatment of wastewater is a kind of wastewater treatment, which uses Anaerobic Microorganisms to degrade organic pollutants in wastewater.  Also known as anaerobic stabilization technology, Since the 1860s in France, because of a variety of anaerobic biological treatment of the equipment has been designed, this method is more and more used in the treatment of food, beverage, paper making, petroleum, chemical, pharmaceutical, organic synthesis and other industrial organic wastewater and urban sewage

Anaerobic biological treatment refers to the process of anaerobic respiration by Anaerobic Microorganisms in the absence of molecular oxygen to convert complex organic matter in water to methane and carbon dioxide and release energy.  Different from the aerobic biochemical treatment process, the hydrogen recipient of domestic sewage treated by anaerobic biological treatment is not molecular oxygen, but carbon, hydrogen, sulfur or combined oxygen.  Therefore, H2, CH4 and H2S are usually produced in the treatment products of anaerobic biological reaction

Correlated Condition

① Temperature: temperature has a significant effect on the rate of anaerobic biodegradation of organic matter.  The suitable breeding temperature of anaerobic organisms is 5 ~ 60℃, and the temperature should be controlled within a certain range according to the requirements in the process of treatment.  

②pH value: should be controlled in 6.8 ~ 7.8 range, the most appropriate is 7.2 ~ 7.6.  The acid-producing bacteria of the second stage are widely existed putrefying bacteria with strong fertility and can grow in the medium with pH value of 4.5 ~ 8.  Methanogens are very demanding in environmental conditions. A pH below 6.4 or above 7.8 inhibits life, and the methanogenic process is suppressed or disrupted to the point of being replaced by decay.  

③ Nutrients: the minimum requirement of nitrogen is 2.5% of organic carbon, and that of phosphate is 0.5% of organic carbon.  

(4) Toxic substances: cyanide, heavy metals, chloroform, carbon tetrachloride, sulfide, benzene and so on have an inhibitory effect on the anaerobic process, the concentration of these substances should be controlled.  For example, cyanide concentration should be less than 25 mg/l, sulfate concentration should be less than 5000 mg/l, benzene concentration should be less than 200 mg/l, synthetic detergent (ABS) concentration should be less than 20 ~ 40 mg/l, etc.  As for the allowable concentration of harmful substances, especially heavy metal ions, the regulations of various countries and the experimental data put forward by scholars differ greatly from each other, which needs to be further studied.  

(5) anaerobic environment: molecular oxygen is not allowed to exist, so REDOX potential should be controlled.  The REDOX potential should be from -560 to -600 millivolts at high temperature and from -300 to -350 millivolts at medium temperature.  In order to maintain anaerobic environment, anaerobic biochemical treatment equipment should not leak.  Facultative anaerobic bacteria and aerobic bacteria brought into the water will consume oxygen and have a positive effect on the anaerobic environment.