Treatment of Preserved Fecal Sludge Using Anaerobic Digestion.

Kanunnikov³

et al. 2021

Appl Biochem Microbiol

Biocidal agents (BAs) are widely used in environmentally safe toilet complexes (ESTC) of passenger railcars to suppress microbial activity in fecal sludge (FS). The subsequent disposal of BA-containing FS at municipal sewage treatment facilities adversely affects their work due to the loss of activated sludge. The antimicrobial properties of BAs based on quaternary ammonium compounds (QAC) and polyhexamethylene guanidine (PHMG), as well as methods for its neutralization, have been studied. It was confirmed that BAs based on QAC and PHMG have an antimicrobial effect on various groups of bacteria, reducing their number by 10-100 or more times. It was found that FS contains two groups of microorganisms with different sensitivities to BA. Methods for the deactivation of BA antimicrobial action in FS were tested with (1) a deactivating agent; (2) incubation with thermophilically digested wastewater sludge as a source of the methanogenic microbial community; and (3) chemical deactivation via acidification or alkalization. The highest efficiency was obtained from thermophilic anaerobic digestion with the pretreatment of FS with a strong acid.

Section: Comparative Characteristics and Economical Assessment Of Methods For Ba Deactivationmentioning

confidence: 99%

Antimicrobial Properties of a Biocide Based on Quaternary Ammonium Compounds plus Polyhexamethylene Guanidine and Possible Methods for Its Deactivation

Litti

Kanunnikov³

et al. 2021

Appl Biochem Microbiol

“…One of the new uses for these biocidal agents is as a component of a chemical toilet additive designed to deodorize fecal waste and control microbial activity. The combined use of QAC and PHMG as biocides to prevent the biodegradation of human waste products by saprotrophic microorganisms and eliminate an unpleasant odor in fecal sludge (FS), for example, in environmentally safe toilet complexes (ESTC) of passenger railcars, has the task of preserving human waste products until their subsequent processing or disposal [ 42 , 43 ]. However, when disposed of in municipal wastewater treatment plants (WWTPs), such waste poses a potential threat, as it negatively affects activated sludge, inhibiting the processes of nitrification, denitrification, and biochemical oxygen demand (BOD) [ 44 , 45 ].…”

Section: Introductionmentioning

confidence: 99%

Didecyldimethylammonium Chloride- and Polyhexamethylene Guanidine-Resistant Bacteria Isolated from Fecal Sludge and Their Potential Use in Biological Products for the Detoxification of Biocide-Contaminated Wastewater Prior to Conventional Biological Treatment

Лойко

Kanunnikov²,

et al. 2022

Biology

Toxic shock caused by the discharge of biocide-contaminated fecal sludge (FS) from chemical toilets to conventional wastewater treatment plants (WWTP) can be a major problem in activated sludge operation. It is necessary to develop new environmental approaches to mitigate the toxicity of biocides in order to avoid degrading the performance of WWTP. “Latrina”, a chemical toilet additive containing didecyldimethylammonium chloride and polyhexamethylene guanidine, is widely used in environmentally safe toilet complexes (ESTC) on Russian railway trains to deodorize FS and control microbial activity. In this work, seven biocide-resistant bacterial strains were isolated and identified from the FS of ESTC. The values of the minimum inhibitory and bactericidal concentrations of biocides for the isolated strains were 4.5–10 times higher than for the collection microorganisms. The bacterium Alcaligenes faecalis DOS7 was found to be particularly resistant to “Latrina”, the minimum inhibitory concentration of which was almost 30 times higher than recommended for ESTC. Biological products based on isolated bacterial strains proved to be effective for FS biodegradation under both aerobic and anaerobic conditions. The results of the biochemical oxygen demand test and the newly developed disk-diffusion bioassay confirmed that isolated strains contribute to reducing toxicity of biocidal agents in FS. Hyper-resistance, non-pathogenicity, and potential plant growth-promoting ability make A. faecalis DOS7 promising for use in various biological products for wastewater treatment and bioremediation of soils contaminated with biocides, as well as in agriculture to increase plant productivity.

Antimicrobial Properties of a Biocide Based on Quaternary Ammonium Compounds plus Polyhexamethylene Guanidine and Possible Methods of Its Deactivation

Kanunnikov²,

Akselrod³

et al. 2020

Biiotehnologiâ (Mosk.)

Biocidal agents (BA) are widely used in environmentally safe toilet complexes (ESTC) of passenger railcars to suppress microbial activity in fаecal sludge (FS). Subsequent disposal of BA-containing FS at municipal sewage treatment facilities adversely affects their work due to the loss of activated sludge. The antimicrobial properties of BA, based on quaternary ammonium compounds (QAC) and polyhexamethylene guanidine (PHMG), as well as methods for its neutralization, have been studied. It was confirmed that BA based on QAC and PHMG has an antimicrobial effect on various groups of bacteria, reducing their number by 10-100 or more times. It was found that FS contains two groups of microorganisms with different sensitivity to BA. Methods for deactivation of the BA antimicrobial action in FS were tested using: (1), a deactivating agent; (2), incubation with thermophilically digested wastewater sludge as a source of the microbial methanogenic community; and (3), chemical deactivation by acidification or alkalization. The highest efficiency was shown by the method of deactivation of BA via thermophilic anaerobic digestion with pretreatment of FS with a strong acid biocide, fаecal sludge of ESTC of passenger railcars, antimicrobial activity, quaternary ammonium compounds, polyhexamethylene guanidine, deactivator, methanogenic microbial community This work was financially supported by the Ministry of Science and Higher Education of the Russian Federation.