Microbiological Control in Decontamination of Sludge from Wastewater Treatment Plant

Abstract

Dynamics of the microbiological indicators of fresh sludge from wastewater treatment plants with a concentration of CaO, 10% and 20%, and ash, −30% and 50%, and treated with quicklime, ash, and microbial fertilizer for a 50-day period of composting were studied. The influence of temperature, water content, and oxygen on the development of microbes was established in laboratory conditions. Microbiological analysis included the determination of non-pathogenic (non-spore-forming bacteria, bacilli, actinomycetes, micromycetes, bacteria digesting mineral nitrogen), and pathogenic (Salmonella, Listeria, Escherichia coli, Enterococcus, Clostridium perfringens) microorganisms. Of the beneficial microflora in the sludge before treating, the amount of non-spore-forming bacteria was the highest, followed by bacilli and micromycetes. It was found that actinomycetes were absent in the untreated sludge. Clostridium perfringens occupied a major share in the composition of the pathogenic microflora, followed by Escherichia coli, Enterococcus, and Listeria. The best results for decontamination of the sludge were obtained by adding 20% quicklime and 50% ash. Alkalization of the sludge after treatment led to the destruction of pathogenic microflora but also reduced the number of beneficial microorganisms. The decrease in pH during the study period determined the redevelopment of pathogenic microflora. Combined variants with lime or ash and microbial fertilizer showed better results for the development of non-pathogenic microflora and the destruction of pathogens.

Characterization of the Pathogenic Potential of the Beach Sand Microbiome and Assessment of Quicklime as a Remediation Tool

“…We are aware that quicklime needs wise management decisions before using either in the terrestrial or aquatic environment, since in water at high concentrations can be dangerous to mollusks and fish [ 44 ]. Compared to the CaO concentrations used to treat sludge from wastewater treatment plants (up to 20%, w / v ) [ 14 ], the amounts used in this study are much lower. Nevertheless, precautions are needed before applying it specifically as a disinfectant, and more studies are needed on its potential application in beach sand.…”

“…Reported remediation measures include sand removal and treatment by chlorine, to restore the biosafety sand quality [ 1 ]. Besides, quicklime used at 10–20% concentration ( w / v ) was reported as an effective treatment for highly contaminated sludges from wastewater plants [ 14 ]. Based on these observations, we tested the potential use of quicklime as a possible rapid sand decontamination method, by using low concentrations of quicklime (1–3%, w / w ) mixed with sand, and analyzing over time its impact on the whole beach sand microbial population, as well on the fraction of potential human pathogens and on the environmental microbes.…”

The Development of Anammox and Chloroflexi Bacteria during the Composting of Sewage Sludge

“…However, this could be beneficial since the results presented by Malcheva et al showed that the creation of an alkaline environment led to a reduction in the number of beneficial microorganisms. This can be used to reduce or destroy pathogenic microorganisms in sewage sludge, compost, and organic waste [27].…”

“…Sustainability 2022, 14, x FOR PEER REVIEW 8 of 11 reduce or destroy pathogenic microorganisms in sewage sludge, compost, and organic waste [27]. Considering the large group of Proteobacteria in the analyzed samples, it should be noted that two classes of microorganisms dominated: Alphaproteobacteria and Gammaproteobacteria, for which 18 and 16 representatives were identified, respectively (Figure 4).…”

Application of microalgae in wastewater: opportunity for sustainable development

“…In addition, the use of microalgae in effluent sanitation is crucial to reducing or eliminating pathogens through mechanisms such as pH changes, nutrient competition, fixation, sedimentation, presence of biocontrol agents (Dar et al, 2019). During photosynthesis, an increase in pH and oxygen concentration occurs, which affects the growth of pathogens such as total and fecal coliforms, Salmonella, Clostridium, and Enterococcus (Delanka- Pedige et al, 2019;Cho et al, 2022;Malcheva et al, 2022). Many produced microalgae metabolites have an antimicrobial effect, being more marked in gram-positive bacteria than in gram-negative bacteria, a difference that is linked to the changes evidenced in the type of cell wall structure (Ramírez- Mérida et al, 2015a;Polat et al, 2023).…”