Microwave can be used alone, or it can be pooled with various oxidants and catalysts, also it can be coupled with some advanced oxidation processes such as UV (photolysis) or photocatalysis (UV/titanium dioxide, TiO2). In old times the microwave was coupled only H2O2 to destroy pollutants. For this reason, the microwave technology creates new fields to search enhanced catalytic degradation. For enhancing the degradation of organic pollutants under microwave, various microwave absorbing materials with high surface area and wide pore size distribution have been developed. After using a microwave-absorbing material, for example activated carbon, hot-spots are occur on the surface of this carbon; thus, produces selective heating, spur in the molecular rotation and finally decreases the activation energy. Also, the efficiency of microwave on decreasing polution is amplified via coupling the microwave with photolysis and photocatalysis. A basic understanding of microwave theory, its application in the elimination of environmental pollution, and the various combinations of microwave applications, such as combining microwave with other treatment techniques are useful to treat water and also waste water.
The waste water treatment is a process which is used to seperate the organic material and contaminants from waste water. There are various processes to make it, but the microwave technology is more rapid and effective way to make. Microwave is a powerful tool in the degradation of various organic compounds including pesticides, ammonia nitrogen and organic dyes. The energy of one mole of photon from microwave at a frequency range of 1–100 GHz is equal to 0.4–40 J. However, there is need to some compounds to couple microwave, because the energy of microwave is not enough to disrupt the chemical bonds of many organic compounds. Therefore, MW has been combined with adsorbents, catalysts and advanced oxidation processes for increasing the treatment efficiency of various pollutants and also to shorten the reaction time. 
Applications of microwave technology to wastewater treatment
Sewage Sludge Treatment Using Microwave Enhanced Advanced
Sewage sludge has lots of recycle carbon and nutrients. The only thing to manage is developing a sustainable management strategy that can effectively recover these nutrients and carbon source, and produce a useful product at the same time. These problem was solved in the University of British Columbia. They developed an application of microwave enhanced advanced oxidation process (MW/H2O2-AOP) for nutrients release and solids disintegration from sewage sludge.
The huge volume of the sludge as an end product is one of the biggest challanges in waste-water treatment industry. Treatment and disposal of sewage sludge from wastewater treatment plants can account for up to 50-60 % of the total cost of wastewater treatment. Yet, the processes are that residual sludge is digested, incinerated, deposited in landfills, or used as fertilizer through agricultural land application. To handle and treat this sludge effectively, there is a need to work up; thus, a microwave enhanced advanced oxidation process (MW/H2O2-AOP) for sludge treatment has been developed at the University of British Columbia. Most of sludge suspended solids was disintegrated at temperatures at 80 ºC and above. A significant amount of nutrients and metals were also released into the solution.