Influence of Innate Sludge Factors and Ambient Environmental Parameters in Biosolids Storage on Indicator Bacteria Survi
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REVIEW
Influence of Innate Sludge Factors and Ambient Environmental Parameters in Biosolids Storage on Indicator Bacteria Survival: A Review S. Fane1 · P. Vale2 · Y. Bajón‑Fernández1 · E. Cartmell3 · A. Nocker4 · J. Harris1 · S. Tyrrel1 Received: 28 March 2019 / Accepted: 21 October 2019 © The Author(s) 2019
Abstract The potential health risks associated with sludge cake application to agricultural land are managed by controlling the levels of Escherichia coli (E. coli) bacteria which indicate the risk of pathogen transfer. Analyses undertaken following postdigestion sludge dewatering have shown unpredictable levels of E. coli increase in stored sludge cake. Presently there is limited understanding on environmental parameters controlling the indicator bacteria density in storage and the contributory effects dewatering may have. This review aims to establish the state of current knowledge on innate and environmental factors influencing E. coli dynamics and survival in biosolids. A key factor identified is the effect of mechanical dewatering processes, which transform the sludge matrix environmental conditions through the increased availability of growth factors (e.g. nutrient and oxygen). Examples of storage practices from the agricultural and food industries are also discussed as successful methods to inhibit bacterial growth and survival, which could be extrapolated to the biosolids sector to regulate E. coli concentrations. Graphic Abstract
Keywords Biosolids · Sludge treatment · Compliance · Storage · Temperature · Nutrient availability · Modified atmosphere * S. Tyrrel [email protected] Extended author information available on the last page of the article
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Statement of Novelty Increases in levels of pathogenic indicator bacteria are frequently observed in stored biosolids. However, little information is known of the environmental conditions prevailing in stored sludge cake and limited advice exists for the reduction of pathogenic indicators in biosolids during storage. This review aimed to establish the current state of knowledge on factors influencing E. coli growth and survival in stored biosolids. A key factor identified is the effect of mechanical dewatering processes, which transform the sludge matrix environmental conditions through the increased availability of growth factors (e.g. nutrient and oxygen). Examples of storage practices from the agricultural and food industries, such as ensiling and modified atmosphere packaging, are also discussed and might give indication of methods to inhibit bacterial growth and survival in biosolids.
Introduction The markets for sludge application to agricultural land are changing. Regulatory reform by the UK’s Water Industry Regulator on sludge production and trade will encourage the delivery of efficiencies and higher product quality standards by 2020 [1]. Sludge has value in biogas energy production and the sale of biosolids to farmers as an alternative to manufactured fertiliser [1]. The improvement of product quality standards
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