A study of the effect of isothiazolones on the performance and characteristics of a laboratory‐scale rotating biological contactor

• Published in: Journal of applied microbiology Vol. 91; no. 1; pp. 93 - 103
• Main Authors: Laopaiboon, L., Smith, R.N., Hall, S.J.
• Format: Journal Article
• Language: English
• Published: Oxford UK Blackwell Science Ltd 01.07.2001; Blackwell Science; Oxford University Press
• Subjects: Adenosine Triphosphate - analysis; Bacteria - drug effects; Biofilms - drug effects; Biofilms - growth & development; Biological and medical sciences; Biological treatment of waters; Biotechnology; Environment and pollution; Equipment Contamination; Fluoresceins - analysis; Fundamental and applied biological sciences. Psychology; Hydrolysis; Industrial applications and implications. Economical aspects; isothiazolone; Oxidation-Reduction; Oxygen - metabolism; rotating biological contactors; Thiazoles - pharmacology; Performance evaluation; Chemical oxygen demand; Biofilm; Microorganism culture; Laboratory scale; Waste water purification; Biocide; Biological purification; Rotating biological contactor
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1046/j.1365-2672.2001.01345.x

Aims: To study the effect of the isothiazolone biocide (Kathon WT) on the performance of laboratory‐scale rotating biological contactors (RBCs) and their component biofilms. Methods and Results: Biofilms were established on the RBCs and then exposed to 0·7–15 p.p.m. isothiazolones. Young, 1‐week‐old, biofilms were found to attain treatment efficiency equal to that of mature, 2‐month‐old, biofilms. Isothiazolone concentrations at 3 p.p.m. and above caused a progressive decline in treatment efficiency and 15 p.p.m. isothiazolones inhibited all microbial activity and resulted in the death of the biofilms. Bio‐oxidation and the biodegradation of isothiazolones within the biofilms ontinued unhindered at concentrations which caused the total inhibition of planktonic bacteria. Conclusions: There was at least a 10‐fold difference in susceptibility of planktonic and biofilm bacteria to isothiazolones. The chemical oxygen demand (COD) test was shown to be a reliable tool for investigating the efficiency of wastewater treatment units when the influent contains isothiazolones, while the biochemical oxygen demand (BOD) was unreliable due to the inhibition of bio‐oxidation by the biocide. Significance and Impact of the Study: The results show that RBCs can be used to treat effluents containing isothiazolones at concentrations up to 1·5 p.p.m.