Effect of Thermal Drying and Chemical Treatments with Wastes on Microbiological Contamination Indicators in Sewage Sludge

Abstract

This work aims to evaluate the microbiological contamination of sewage sludge (SS) collected in urban wastewater treatment plants (WWTP) from Portugal. Two types of SS were considered: urban mixed (UM) and from anaerobic digestion (AD). The two types of samples were characterized in relation to the main physical and chemical parameters, as well as the microbiological contamination (Escherichia coli and Salmonella spp). Then, sanitation tests were conducted through thermal drying and chemical treatments. Towards a circular economy, industrial alkaline wastes (green liquor dregs -GLD, lime mud, coal fly ash, eggshell) were tested as alternatives to lime. Only six out of nineteen samples complied with the legal limits for both microorganisms. However, drying at 130 • C sanitized selected samples below the E. coli limit, regardless of the initial moisture or contamination. Additionally, CaO (obtained from eggshell) led to the complete elimination of E. coli at any dosage studied (0.05-0.15 g/g SS wet basis ). GLD evidenced the ability to reduce E. coli contamination at room temperature, but not enough to comply with the legal limit. In general, this work highlights the need to sanitize the SS before its application to the soil, and the positive role of some wastes on this goal.

Impact of Calcium Oxide on Hygienization and Self-Heating Prevention of Biologically Contaminated Polymer Materials

“…Increase of pH induced by the addition of CaO causes permanent changes in ionization of the structural components of cellular proteins of microorganisms (especially in the case of anionic and carboxylic groups). This leads to irreversible modifications of their structures and disrupts the activity of the enzymes [2]. As suggested by Bień [3], the hydration of sewage sludge may reach as much as 99%.…”

Agricultural and non-agricultural directions of bio-based sewage sludge valorization by chemical conditioning

“…Studies show the need to disinfect sewage sludge before it is used, especially in agriculture (Santos et al 2020). Experimental alkaline treatment to eliminate pathogens (bacteria and worm eggs) was also carried out by Lopes et al (2020).…”

“… (Stylianou et al 2007 ) SS 8.34 2.59 P 2 O 5 0.35 K 2 O 0.12 CaO 0.41 MgO n.a. (Santos et al 2020 ) Fermented sludge 6.6 1.6 n.a. n.a.…”

Efficiency of application of the microbiological method of waste water treatment to remove hexamethylendiamine

“…Treatment of sewage from HMD is an actual problem for the enterprise "Chernihiv Khimvolokno" (Ukraine), on the territory of which there is an artificial pond, in which about 1600 m 3 of industrial wastewater from the production of polymer "anide" containing HMD has been stored for more than 25 years. The concentration of HMD in the wastewater of chemical fiber production reaches very high values, up to 2540 mg/dm 3 [Santos et al, 2012]. The gist of treatment biotechnology lies in the employment of the widest range of hydrobionts in the process of sewage treatment, starting with the bacteriadestructors of the most dangerous, toxic synthetic chemical substances (xenobiotics), and ending with high-concentration chemicals [Shatokhina 2013].…”