Bismuth dimercaptopropanol (BisBAL) inhibits formation of multispecies wastewater flocs

Abstract

Aims: To determine the ability of a bismuth thiol to control floc formation in a multispecies population of micro‐organisms obtained from the activated sludge unit of a wastewater treatment plant. The molecular level mechanisms by which bismuth‐2‐3‐dimercapto‐1‐propanol (BisBAL) inhibits bioaggregation are also elucidated. Methods and Results: Micro‐organisms were grown over a 3‐day period in a batch system by adding glucose as an electron donor to stimulate short‐term heterotrophic activity. Extracellular polymeric substances (EPS) produced by activated sludge micro‐organisms during exponential and stationary growth phases in the presence and absence of BisBAL were characterized using colorimetry, X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. BisBAL at its minimum inhibitory concentration (MIC, 10 μmol l−1) was most effective in suppressing microbial floc formation. The principal effect of sub‐inhibitory concentrations of BisBAL was to decrease total EPS production while largely preserving homology. Conclusions: Antifouling and bactericidal properties of BisBAL arise from its ability to reduce EPS expression and preferentially suppressing acidic and O‐acetylated carbohydrates and certain protein secondary structures viz. β‐structures, random coils, and α‐and 3‐turn helices. As micro‐organisms exhibited a much weaker tendency to aggregate at lower concentrations of these specific EPS components, they also appear to be important for the formation of microbial flocs and bioaggregates. Significance and Impact of the Study: BisBAL was shown to be highly effective against multispecies microbial aggregation. Novel bismuth‐based biocides could also be potentially employed to control excess sludge production in wastewater treatment systems by inhibiting EPS expression.

Evaluating the role of total organic carbon in predicting the treatment efficacy of biosand filters for the removal ofVibrio choleraein drinking water during startup

“…EPS was extracted from the schmutzdecke of each BSF using a cation exchange resin as previously described (Frolund et al . ; Badireddy and Chellam ). Protein was quantified by the Modified Lowry Protein Assay Kit (Pierce Biotechnology, Rockford, IL) with bovine serum albumin standards.…”

“…Protein was quantified by the Modified Lowry Protein Assay Kit (Pierce Biotechnology, Rockford, IL) with bovine serum albumin standards. Carbohydrates were measured using the phenol–sulphuric acid method against glucose standards (Badireddy and Chellam ). Uronic acid was determined as described elsewhere (Badireddy and Chellam ).…”

“…Carbohydrates were measured using the phenol–sulphuric acid method against glucose standards (Badireddy and Chellam ). Uronic acid was determined as described elsewhere (Badireddy and Chellam ). In accordance with previously published work (Frolund et al .…”

Effect of Lipophilic Bismuth Nanoparticles on Erythrocytes

“…A stock solution of 2 : 1 molar ratio of Bi (Bis) to 2,3dimercapto-1-propanol (BAL) (a.k.a. BisBAL) served as a cationic precursor for the BisBAL nanoparticles and the choice of molar ratio was based on the previous work, which showed BisBAL was stable over a wide pH range (4-11) and effective against microbial biofilm formation [29]. During the course of BisBAL reduction with NaBH 4 , the pink color of soluble BisBAL instantly transformed to a black colored suspension composed of BisBAL nanoparticles.…”

Bismuth Thiols as Anti-Biofilm Agents

“…They also hold promise as environmentally responsible solutions to the problem of biofouling in industrial processes. 19,20…”