The Influence of Changes in Concentration and Temperature upon the Bactericidal Activity of Formaldehyde in Aqueous Solutions
Although formaldehyde in aqueous solution (formalin) is an important and widely used disinfectant, there is very little information available concerning the exact effect of changes in either concentration or temperature upon its bactericidal activity. An experimental study was therefore made of the bactericidal activity of formaldehyde. This study was conducted along the lines of previous studies of the bactericidal activities of phenols and alcohols (Tilley, 1939, 1942).
The effect of disinfectants and antiseptics on co- and cross-selection of resistance to antibiotics in aquatic environments and wastewater treatment plants
The outbreak of the SARS-CoV-2 pandemic led to increased use of disinfectants and antiseptics (DAs), resulting in higher concentrations of these compounds in wastewaters, wastewater treatment plant (WWTP) effluents and receiving water bodies. Their constant presence in water bodies may lead to development and acquisition of resistance against the DAs. In addition, they may also promote antibiotic resistance (AR) due to cross- and co-selection of AR among bacteria that are exposed to the DAs, which is a highly important issue with regards to human and environmental health. This review addresses this issue and provides an overview of DAs structure together with their modes of action against microorganisms. Relevant examples of the most effective treatment techniques to increase the DAs removal efficiency from wastewater are discussed. Moreover, insight on the resistance mechanisms to DAs and the mechanism of DAs enhancement of cross- and co-selection of ARs are presented. Furthermore, this review discusses the impact of DAs on resistance against antibiotics, the occurrence of DAs in aquatic systems, and DA removal mechanisms in WWTPs, which in principle serve as the final barrier before releasing these compounds into the receiving environment. By recognition of important research gaps, research needs to determine the impact of the majority of DAs in WWTPs and the consequences of their presence and spread of antibiotic resistance were identified.
A Note on the Variation of the Rate of Disinfection with Change in the Concentration of the Disinfectant
In a recent paper by Miss Chick on “The Laws of Disinfection”, it was pointed out that disinfection of bacteria is strictly analogous to a chemical reaction in which individual bacteria play the part of molecules. Thus, if n be the number of bacteria present at any time t during dis-infection, , where K is a constant. Also, if K1, K2 are these constants for two different temperatures is also constant, i.e. Arrhenius' formula for the temperature coefficient of chemical reactions holds good in the case of bacteria as well. In addition to this, it was found that the relation between the concentration of the disinfectant and the time of disinfection (that is, the time required to reduce the original number of bacteria by a given percentage) might abe approximately expressed by the empirical law where C is the concentration at time t.