Biological Activated Carbon Process for Water Treatment
The biological activated carbon (BAC) process mainly utilizes the pore structure and surface area of activated carbon to achieve high efficiency as for growing concern of the treatment of water containing more and more kinds of pollutants nowadays. Compared with using solely activated carbon method or biological method, the combined process prolongs the service life of activated carbon, improves the dewatering and anaerobic digestion of sludge, and has been used for various types of wastewater (chemical, printing, synthetic fibers, etc.).
The process uses activated carbon as a carrier, and forms a biofilm on the surface of the carbon. The pollutants in water are adsorbed by activated carbon, and oxidatively decomposed by microorganisms.
Influence of the turbidity of influent
High turbidity of the influent and concentration of suspended solids contained can easily block the pores of activated carbon, resulting in a greatly reduced adsorption capacity and increased difficulty of the subsequent treatment. And this will also reduce the contact area between microorganisms and activated carbon.
Influence of preprocessing
Pre-oxidation can decompose macromolecular organic matters into smaller molecules. It has been studied that ozone, potassium permanganate, biological preprocessing can improve various indexes of removal ability.
Application of biological activated carbon process in water treatment
The textile industry requires huge water consumption and its wastewater contains a large number of chemicals that are quite difficult to deal with. The biological activated carbon process utilizes the metabolic capabilities of bacteria, fungi, algae, etc., to react with organic and inorganic compounds under suitable conditions (oxygen concentration, pH, nutrients). The process is usually carried out in a bioreactor with adequate aeration and agitation control arrangement. Biodegradation methods are considered cost-effective for long-term use though with high investment costs depending on the equipment used.
This wastewater can be generated during processes ranging from petroleum extraction, refining, transportation, to storage. The volatile substances, and part of the petroleum will pollute the air and groundwater. In addition, the main constituent elements of petroleum are carbon and hydrogen, and excessive hydrocarbon content may cause combustion. A kind of bacteria that can degrade petroleum hydrocarbons has been found in petroleum contaminated areas and immobilized on activated carbon. Compared with other bacteria, it significantly increases the removal rate of COD and oils in water.
Humus in raw water
Humus is the main organic carbon in raw water and it is easy to react with chlorine, forming carcinogenic disinfection by-products. It will also affect the stability of residual chlorine, leading to the accelerated growth of microorganisms in pipelines.
Combining ozone and biological activated carbon is one of the mostly-used techniques in water plants. As mentioned above, ozone can oxidize macromolecular, reducing the operation difficulty in latter processes. And using a large amount of chlorine can be prevented as ozone has the ability of sterilization and disinfection.
Wastewater in ceramic, food, pharmaceutical, and other industries may contain various anionic and cationic synthetic dyes. Dyes that are toxic and carcinogenic can cause harm to human and aquatic animals. For example, crystal violet has a complex and stable molecular structure and is difficult to degrade. There are various methods for treating dyeing wastewater, among which, the adsorption method is considered to be the most suitable method due to its high efficiency, low cost, simple operation and availability of adsorbents such as activated carbon.
Biological activated carbon fluidized bed has high efficiency in removing various kinds of pollutants. It also has strong resistance to shock loading that can prevent sludge bulking.