Wastewater treatment is an issue in many countries both developed and underdeveloped. The need to treat efficiently these wastewaters to reduce the levels of contamination on them is always present. Traditionally, wastewaters have been treated using biological processes and physico-chemical processes such as denitrification, phosphorous removal, reverse osmosis, micro and ultra-filtration, chemical precipitation, carbon adsorption, electro-dialysis, and ion-exchange.
Sonochemistry, the use of acoustic waves, can improve wastewater treatment. A variety of methods to treat polluted water using sonochemistry have been used. More specifically, the combination of electrolysis and sonochemistry, that is Sonoelectrochemistry, has proved to be very successful in treating both drinking or polluted water. Traditionally, chlorine is produced by electrolysis of hydrochloric acid on effluents. This process produces around 1% of chlorine, the active disinfectant. But, if ultrasound is coupled with electrolysis then efficiency of chlorine production increases dramatically. This way more wastewater can be treated with same amount of hydrochloric acid electrolyzed.
Removal of phenols from toxic waste also is improved significantly when acoustic waves are used coupled with traditional phenol-removal methods. Normally phenol in removed from industrial effluents by a process electrochemical oxidation. But if a sonochemistry device is coupled with electrical oxidation then efficiency increases by as much as 160% when compared with the electrochemical oxidation alone. Also, sonoelectrochemical destruction of aromatic compounds in water samples has been obtained using very low acoustic waves frequencies.
Another interesting technology that could be used to increase the efficiency of wastewaters treatments is the use of a process called sonoelectrical coagulation. Traditionally, electrocoagulation has been used for destruction of a variety of pollutants (mainly inorganic and organics). Electrocoagulation method of treating wastewaters in which effluents are electrolyzed with special electrodes that release coagulant precursors (aluminum iron ions) into the treated sample. The electrocoagulation process has a variety of issues that prevents to get the full “cleaning” effect. Coupling electrocoagulation with sonochemistry gets rid of many of those obstacles increasing its efficiency.
Recently, it has been demonstrated that heavy metals can be efficiently be recovered from photographic waste effluents using sonoelectrochemical methods. For example, traditional electrochemical removal of mercury from photographic waste effluents could take up to 7 hours to reduce Hg levels to 1 ppm. By using sonochemistry (in addition to electrochemistry) the processing time can be reduced to 2.2 hours
Sonochemistry in a new technology that can be utilized to treat a variety of industrial effluents including chemical dyes, chemical wastes, mercury contaminated waters, fluorinated waters, mine effluents, etc. Efficiencies of scale can be realized if the technology is incorporated in current wastewater treatment processes.