Two strategies for phosphorus removal from reject water of municipal wastewater treatment plant using alum sludge

Abstract

In view of the well recognized need of reject water treatment in MWWTP (municipal wastewater treatment plant), this paper outlines two strategies for P removal from reject water using alum sludge, which is produced as by-product in drinking water treatment plant when aluminium sulphate is used for flocculating raw waters. One strategy is the use of the alum sludge in liquid form for co-conditioning and dewatering with the anaerobically digested activated sludge in MWWTP. The other strategy involves the use of the dewatered alum sludge cakes in a fixed bed for P immobilization from the reject water that refers to the mixture of the supernatant of the sludge thickening process and the supernatant of the anaerobically digested sludge. Experimental trials have demonstrated that the alum sludge can efficiently reduce P level in reject water. The coconditioning strategy could reduce P from 597-675 mg P/L to 0.14-3.20 mg P/L in the supernatant of the sewage sludge while the organic polymer dosage for the conditioning of the mixed sludges would also be significantly reduced. The second strategy of reject water filtration with alum sludge bed has shown a good performance of P reduction. The alum sludge has P-adsorption capacity of 31 mg-P/g-sludge, which was tested under filtration velocity of 1.0 m/h. The two strategies highlight the beneficial utilization of alum sludge in wastewater treatment process in MWWTP, thus converting the alum sludge as a useful material, rather than a waste for landfill.

Application of waterworks sludge in wastewater treatment plants

“…Increasing interest in the usage of WWS for the removal of phosphate at the WWTP is seen in the past two decades in the form of many laboratory studies (e.g. Babatunde and Zhao 2010;Ippolito et al 2003;Yang et al 2009;Zhao et al 2007); however, the reuse of WWS at WWTP is rarely seen in practice. The reported studies on phosphate removals with WWS show that the sorption of phosphate is a two-stage process: a quick sorption followed by slow sorption (cited in Ippolito et al 2011).…”

“…Hence the majority of studies on WWS reuse have been performed with aluminium-rich WWS (e.g. Babatunde and Zhao 2010;Ippolito et al 2003;Makris et al 2004;Yang et al 2009;Zhao et al 2007) and very few were based on ironrich WWS (e.g. Makris et al 2004;Leader et al 2008).…”

A promising approach of reject water treatment using a tidal flow constructed wetland system employing alum sludge as main substrate

“…One strategy was the use of the thickened alum sludge for co-conditioning and dewatering with the anaerobically digested sludge in MWWTP. The other strategy involves the use of dewatered alum sludge cakes in a fixed bed for P immobilization in reject water (Yang et al, 2009). However, from a holistic point of view, the process for reducing nutrient feedback and accumulation in MWWTP should duly consider N, P and OM removal, rather than P itself from the recycled reject water.…”

Water treatment sludge for phosphate removal from the effluent of UASB reactor treating municipal wastewater

“…WTS can act as skeleton builder in the mixed sludge which makes the mixed sludge more incompressible and enhance the dewaterability (Lai and Liu, 2004). Also the phosphate concentration in the supernatant of the mixed sludge will decrease due to adsorption by WTS (Yang et al, 2009). The combined sludge can be dried in sludge drying beds and can be used for land application (Fig.…”

“…High affinity of amorphous Al and Fe present in WTS for phosphorus along with large surface area of WTS makes WTS a potential adsorbent for phosphorus (Oliver et al, 2011;Wang and Pei, 2013;Yang et al, 2006). WTS has been used as adsorbent for phosphorus removal from sewage (Babatunde et al, 2008), agricultural wastewater , storm water runoff (O'Neill and Davis, 2012), aquaculture processing water (Mortula and Gagnon, 2007) and supernatant of the sludge thickening process and anaerobically digested sludge (Yang et al, 2009). No studies have been reported in the literature on the use of water treatment sludge as a coagulant for phosphate removal from the effluent of UASB reactor treating municipal wastewater.…”