A Review of the Mechanisms of Faecal Coliform Removal from Algal and Duckweed Waste Stabilization Pond Systems | Science Publications

American Journal of Environmental Sciences

A. Andoh¹  H. J. Lubberding¹  E. D.O. Ansa¹  E. Awuah¹  H. J. Gijzen¹  R. Banu¹  W. H.K. Dorgbetor¹ 

关键词: Macro-Invertebrates;    Pathogens;    Performance;    Treatment;    Wastewater;   

DOI  :  10.3844/ajessp.2015.28.34

学科分类：环境科学（综合）

来源: Science Publications

【 摘 要 】

Theuse of eco-technologies for wastewater treatment such as algal and duckweed-basedpond systems is becoming popular in developing countries owing to itsaffordability and efficiency of pathogen removal in warm climates. The pathogenremoval mechanisms of these treatment systems however is still not clearlyunderstood and existing knowledge is also scattered in journals and books ofdifferent disciplines. The purpose of this paper is to provide a concise reviewof knowledge acquired in recent times on faecal coliform removal mechanisms inalgal and duckweed ponds in a comparative way while identifying knowledge gapsthat still exist. This review pays particular attention to little known removalmechanisms such as the role of algal biomass, attachment and sedimentation offaecal coliforms and the role of predation by macro-invertebrates and protozoans.Recent experiments showed that algal ponds, in comparison with duckweed ponds,are more efficient in faecal coliform removal due to the high pH andoxygenation that occur in the former and the rate of inactivation of faecalcoliforms increases with increased algal biomasstill a certain optimum concentration after which it decreases. This optimalalgal concentration for maximum destruction of faecal coliforms can be affectedby the quality and strength of the wastewater. Algae also appeared to have adestructive effect on faecal coliforms even in darkness, a phenomenon that maybe the effect of toxic substances from the algae. Results also show that therole of invertebrates, particularly macro-invertebrates may be more importantin duckweed pond systems. Removal of faecal coliforms through attachment andsedimentation in both duckweed and algal ponds appear to be dependent largelyon concentrations of faecal coliforms present and to some extent on suspendedplant and particulate matter concentrations. Wide variations in removalefficiencies were however observed. We conclude that the wide variations inremoval efficiencies can be addressed by standardizing operating conditions oftreatment systems. Further work is necessary to identify the substances producedby algae which appeared to be toxic to faecal coliforms as well as establishingthe relative importance of predation by protozoans and macro-invertebrates inthe removal of faecal coliforms.

【 授权许可】

Unknown