Aqueous disinfecting agent containing performic acid and peracetic acid process for production and process for use thereof

#The invention is directed towards an aqueous disinfecting agent containing performic acid and peracetic acid, a process for production thereof and also the use thereof for controlling micro-organisms, particularly in aqueous systems.

#For the treatment of aqueous solutions, particularly municipal sewage, surface waters and industrial recirculated waters and waste waters containing micro-organisms, that—for hygienic, operational or environmental reasons—cannot be discharged or re-used in the untreated state, effective treatment processes are necessary. Effective chemical processes that at the same time are environmentally compatible are based on the use of active-oxygen compounds such as disinfecting agents containing, in particular, hydrogen peroxide, peroxyacetic acid and peroxyformic acid, usually designated as peracetic acid and performic acid. The term “disinfecting agent” is to be understood to mean an agent that is suitable for controlling all types of micro-organisms, such as bacteria, viruses, molds and algae; in addition, this agent is suitable for controlling small creatures such as zooplankton.

#It is known that hydrogen peroxide is a moderately effective, mild disinfecting agent with bacteriostatic properties. Whereas H2O2 concentrations of 25 mg/l do inhibit the growth of some bacteria, an effective lowering of the bacterial count requires many hours, even at much higher H2O2 concentrations, or an additional UV irradiation process. Such measures are inadequate and, in addition, not economical for disinfecting large quantities of water, for instance the treatment of water in clarification plants and their outlets.

#A disinfecting agent according to the invention was produced by addition of 20 g formic acid (FA) to 980 g of an equilibrium peracetic acid that contained 2 wt. % peracetic acid (PAA), 1 wt. % acetic acid (AA) and 48 wt. % hydrogen peroxide as well as 2 wt. % H2SO4.

#After a standing time of only 2 hours this solution was employed as a disinfecting agent in comparison with the equilibrium peracetic acid for the treatment of swimming-pool water; quantity used in each case: 10 mg disinfecting agent per l water.

#Pure cultures of the bacterial suspension to be tested were added to a swimming-pool water under standardised conditions, and a concentration of 107 to 108 KBE/ml was adjusted. After addition of the disinfecting agent, samples were taken following an exposure time of either 10, 20 or 30 seconds and, after inactivation of the disinfecting agent, the residual concentration of the test bacteria was determined in these samples and the disinfecting capacity (KRt) was ascertained from this concentration.