Method for treating wastewater and wastewater sludge using a percarboxylic acid

#The present invention relates to a method for treating wastewater and/or wastewater sludge according to the independent claim presented below. The invention relates also to use of percarboxylic acid in odor control and/or in corrosion control.

#Various organic and inorganic compounds can cause problems in wastewater treatment processes, one of the most remarkable of which is bad odor. Hydrogen sulfide is often identified as the predominant odor- and corrosion-causing compound of concern in wastewater treatment systems. Hydrogen sulfide H2S, is naturally generated, when organic matters in the wastewater treatment process are degraded through anaerobic digestion by bacteria. In typical domestic wastewater, microbial reduction of the sulfate ion is the dominant mechanism for sulfide formation.

#Bacteria in wastewater treatment system may respire soluble oxygen, soluble nitrate, or soluble sulfate as sources for terminal electron acceptors to generate energy depending on the type of environment they live in. Soluble oxygen is usually present in fresh wastewater, but is rapidly depleted by biological activity. There is typically very little nitrate present in wastewater, while sulfate is typically abundant. Since little or no nitrate is available, in the absence of soluble oxygen and in the presence of soluble biological oxygen demand, the bacteria begin respiring sulfate to generate energy. To obtain energy, the bacteria must transfer the electron from the electron donor to sulfate, effectively reducing the sulfate to sulfide. The dissolved sulfide combines with hydrogen ions to form hydrogen sulfide, causing odor problems. The rate of sulfide production is dependent upon the concentrations of sulfate ions, organic matter, as well as other factors such as pH, temperature, retention time and stream velocity. Sulfides exist in wastewater in three forms: H2S gas, non-volatile bisulfate HS− and sulfide S2−.

#Example: Odor Control Laboratory Testing Utilizing

#A sample from influent wastewater is grabbed at an influent channel of a municipal wastewater treatment plant. The samples are grabbed in a 1000 ml polypropylene bottle and filled completely to the top to prevent any volatilization of sulfide out of the sample.

#A treating chemical formulation comprising performic acid (PFA) as an active odor controlling agent and all other reagents are prepared just prior to be used.