Abstract
Chemically enhanced primary treatment (CEPT) is a process that uses coagulant and/or flocculant chemicals to remove suspended solids, organic carbon, and nutrients from wastewater. Although it is not a new technology, it has received much attention in recent years due to its increased treatment capacity and related benefits compared to the conventional primary treatment process. CEPT involves both physical and chemical processes. Alum and iron salts are the commonly used coagulants in CEPT. Several types of anionic, cationic, and uncharged polymers are used as flocculants, where poly aluminum chloride (PACL) and polyacrylamide (PAM) are the widely used ones. Some of the coagulants and flocculants used may have inhibitory and/or toxicity effects on downstream treatment and recovery processes. There has been an increasing amount of work on the treatment of wastewaters from various sources using CEPT. These wastewaters can range from municipal/domestic wastewater, combined sewer overflow, landfill leachate, cattle manure digestate to wastewaters from textile industry, pulp and paper mill, slaughterhouse, milk processing plant, tannery and others. In recent cases, CEPT is employed to enhance carbon redirection for recovery and substantially reduce the organic load to secondary treatment processes. CEPTs can remove between 43.1–95.6% of COD, 70.0–99.5% suspended solids, and 40.0–99.3% of phosphate depending on the characteristics of wastewater treated and type of coagulants and/or flocculants used. This article reviews the application, chemicals used so far, removal efficiencies, challenges, and environmental impacts of CEPT.
Highlights
Primary wastewater treatment has been identified as a key area of research in improving the sustainability of wastewater treatment processes [1]
In chemically enhanced primary treatment (CEPT), the major objective is to remove pollutants such as organic carbon and nutrients and concentrate it in the sludge produced, which can be regarded as valuable resources to increase energy recovery
Coagulation increases the ionic strength of the wastewater, which has the effect of compressing the electrical double layer (EDL), which in turn reduces the zeta potential
Summary
Primary wastewater treatment has been identified as a key area of research in improving the sustainability of wastewater treatment processes [1]. There has been an increasing amount of work on the treatment of wastewaters from various sources using CEPT. CEPT provides effective treatment for excess wet weather flows, avoiding high. Effective treatment for excess weather flows, avoiding capital investmentsCEPT for fullprovides biological treatment, with wet infrequent storm events [3]. CEPT consists of adding chemicals (metal salts and/or polymers in of organic polyelectrolytes) to increase the coagulation, flocculation, and sedimentation of the raw form wastewater. The growing environmental issues effective has raised the interest the research into coagulants to global reduceconcern the use with of metal salts [6]. Inclarification recent years, has been used at various wastewater treatment plants for phosphate removal, of CEPT wastewater, reduction various wastewater treatment plants for phosphate removal, clarification of wastewater, in in sludge volume, and increase in surface overflow rates (SORs). Harleman and Murcott [9] provided CEPT application examples from Mexico City, Southern
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