Analysis of the impact of ultrasonic disintegration on changes in the physico-chemical and biological properties of municipal wastewater

Raw municipal wastewater is a reservoir of many physical, chemical and microbiological pollutants. The treatment process carried out in municipal wastewater treatment plants focuses on giving the wastewater physical and chemical properties similar to those of surface waters. It does not take into account the microbiological properties of wastewater. The aim of the conducted research was therefore to determine the impact of ultrasonic disintegration on changes in the physico-chemical and microbiological properties of municipal wastewater. Raw wastewater samples were subjected to ultrasound with a frequency of 26 kHz, and the results of the work allowed to determine the effect of sonication on changes in physico-chemical (pH, biochemical oxygen demand, chemical oxygen demand, total nitrogen, total phosphorus and total suspensions) and microbiological properties (total number of bacteria, coliform, streptococcal faeces, Clostridium bacteria) of raw municipal wastewater. An additional aspect was to carry out biotests of raw wastewater samples to determine their acute toxicity using the Microtox system and Aliivibrio fischeri luminescent bacteria. The obtained results allowed to conclude that the impact of ultrasounds with a frequency of 26 kHz causes a significant reduction in the number of microorganisms present in raw wastewater - by nearly 93% in relation to the total number of bacteria after 10 min of the sonication process and about 73% of bacteria of the Clostridium genus, 98% of coliform, as well as complete reduction of fecal streptococci after 25 min of sonication. In addition, it has been proven that ultrasonic disintegration does not significantly change the physico-chemical properties of raw municipal wastewater or the acute toxicity of the tested wastewater.