Powdered activated carbon coupled with enhanced coagulation for natural organic matter removal and disinfection by-product control: Application in a Western Australian water treatment plant

Abstract

The removal of organic precursors of disinfection by-products (DBPs), i.e. natural organic matter (NOM), prior to disinfection and distribution is considered as the most effective approach to minimise the formation of DBPs. This study investigated the impact of the addition of powdered activated carbon (PAC) to an enhanced coagulation treatment process at an existing water treatment plant on the efficiency of NOM removal, the disinfection behaviour of the treated water, and the water quality in the distribution system. This is the first comprehensive assessment of the efficacy of plant-scale application of PAC combined with enhanced coagulation on an Australian source water. As a result of the PAC addition, the removal of NOM improved by 70%, which led to a significant reduction (80-95%) in the formation of DBPs. The water quality in the distribution system also improved, indicated by lower concentrations of DBPs in the distribution system and better maintenance of disinfectant residual at the extremities of the distribution system. The efficacy of the PAC treatment for NOM removal was shown to be a function of the characteristics of the NOM and the quality of the source water, as well as the PAC dose. PAC treatment did not have the capacity to remove bromide ion, resulting in the formation of more brominated DBPs. Since brominated DBPs have been found to be more toxic than their chlorinated analogues, their preferential formation upon PAC addition must be considered, especially in source waters containing high concentrations of bromide.

Enhanced coagulation with powdered activated carbon or MIEX® secondary treatment: A comparison of disinfection by-product formation and precursor removal

“…The concentrations of these DBP precursors should therefore be kept to a minimum at the point of water disinfection and thereafter (Richardson et al, 2003;Trofe et al, 1980). DBP precursor removal has traditionally focussed on NOM removal, with water treatment methods such as enhanced coagulation (EC) and powdered activated carbon (PAC) adsorption widely used for this purpose (Kristiana et al, 2011). These treatments, however, do not remove halides (Sigworth and Smith, 1972), therefore they increase the bromide to dissolved organic carbon (Br:DOC) ratio and can preferentially form brominated DBPs when bromide is present in sufficient concentration.…”

The enhanced removal of carbonaceous and nitrogenous disinfection by-product precursors using integrated permanganate oxidation and powdered activated carbon adsorption pretreatment

“…PAC is also usually used as an emergency measure to remove algae, taste and odor compounds and other pollutants in raw water with high concentration (Westerhoff et al, 2005;Zhang et al, 2010). Previous studies have reported that PM oxidation or PAC adsorption can reduce and/or increase the formation of several regulated C-DBPs and unregulated N-DBPs by removing and/or chemically transforming precursors prior to disinfection (Chen and Valentine, 2008;Chu et al, 2011;Kristiana et al, 2011;Jiang et al, 2014). However, very little information is available concerning the control of a range of N-DBPs in N-rich waters pre-treated by coupling PM oxidation and PAC adsorption (PM-PAC).…”

Removal of reactive dye from aqueous solution using coagulation–flocculation coupled with adsorption on papaya leaf

“…Activated carbon is used as adsorbent [13][14][15][16] in some combined coagulation-flocculation/ adsorption treatment systems. However, activated carbon is cost prohibitive and neither the regeneration nor the disposal of used carbon is straightforward.…”