Polyaluminium chloride dosing effects on coagulation performance: case study, Barekese, Ghana

Abstract

Alum, the predominant coagulant in conventional drinking water treatment schemes, has various disadvantages including the production of large volumes of sludge, lowering water pH (requiring pH adjustment using lime), limited coagulation pH range of 6.5 to 8.0, etc. At the Barekese Water Treatment Plant in Ghana, an alternative, the polyelectrolyte – Polyaluminium chloride (PAC) is also used in coagulation but limited information is available on the operating conditions required to achieve better performance than alum-based coagulation. The aim of this study was to determine the optimal coagulant dose, mixing speed and operating pH for enhanced performance in water treatment. The effects on the treatment process of three different sets of mixing speed pairs – 180/40, 180/25 and 150/25 revolutions per minute (fast/slow) – in a pH range of 6.5 to 8.0 were investigated. The mixing speed and PAC dose yielding the best coagulation were 150/25 rpm and 15 mg/L respectively. The optimal pH range for PAC coagulation performance was 7.5 to 8.0.

The Efficiency Assessment of Poly-Aluminium Chloride (PAC) in Water Treatment Plant Process: A Case Study at Sultan Iskandar Water Treatment Plant, Johor

“…This is because the existing chemical used in Sultan Iskandar Water Treatment Plant (SIWTP) is Aluminium Sulphate (Alum). Based on the previous study, the formation of floc produced by Alum is particularly fragile (McCurdy et al, 2004;Aziz et al, 2017;Kumar et al, 2020;Liu et al, 2021;Nti et al, 2021). This can make the process of flocculation insufficient.…”

Electrocoagulation Process for Chromium Removal in Leather Tanning Effluents

“…Traditional treatment methods, such as precipitation and chemical coagulation, have limitations in achieving efficient chromium removal. These issues persist due to the prevalent use of PAC (poly aluminum chloride) and PAS (poly aluminum sulfate), known for their poor stability, limited coagulation efficiency, and sluggish floc formation time (Astuti et al, 2022;Aziz et al, 2017;Nti et al, 2021). Moreover, the utilization of PAC contributes to the presence of toxic Al 3+ in processed water, posing potential hazards (Simbarta Tarigan et al, 2021).…”

Application of Response Surface Methodology to Optimize Coagulation Treatment Process of Urban Drinking Water Using Polyaluminium Chloride

“…During water treatment processes, conventional coagulants such as iron and aluminium sulfate are typically used to stimulate particle formation. Alum has been used as a coagulant for a long time, but it has some limitations, including a narrow pH range (6.5 to 8.0) and the development of substantial amounts of aluminium residue during post-treatment [21]. Because of these challenges with alum, better aluminium-based polymers such as polyaluminium chloride (PAC), produced by the gradual titration of a base to aluminium salts, have been widely used in the last few decades to treat urban water because (i) they work well at lower doses, (ii) they have outstanding coagulation and sedimentation properties [22], and (iii) they have a wider pH and temperature range [21,23].…”

“…Alum has been used as a coagulant for a long time, but it has some limitations, including a narrow pH range (6.5 to 8.0) and the development of substantial amounts of aluminium residue during post-treatment [21]. Because of these challenges with alum, better aluminium-based polymers such as polyaluminium chloride (PAC), produced by the gradual titration of a base to aluminium salts, have been widely used in the last few decades to treat urban water because (i) they work well at lower doses, (ii) they have outstanding coagulation and sedimentation properties [22], and (iii) they have a wider pH and temperature range [21,23]. However, their chemistry and aggregation properties are not as well known, and specific information on using polyaluminium coagulants remains a viable approach [22].…”