Effluent pretreatment by iron coagulation applying various dose-pH combinations for optimum particle separation

Abstract

Wastewater reuse often requires particle destabilization and removal to protect water transport systems and membranes from clogging. Flocculation process of activated sludge effluent applying ferric chloride is examined and comparison with alum (aluminium sulfate) application is made in this work. Optimum flocculation conditions are determined based on the removal efficiency of different particle size groups and on turbidity as a function of coagulant dosage and pH. Results show that the best removal for ferric chloride coagulant occurs at pH 4-5 and dosage of 20-30 mgl−1. Settled water total particle count (TPC) of particle size ≥2μm was reduced by more than 99%, while turbidity removal reached 86%. Zeta potential measurements and visual observations indicate domination of adsorption and charge neutralization mechanisms. Best removal with alum occurred at pH 6-7 while dosing 30 mgl−1 and higher. Destabilization mechanism of adsorption and sweep coagulation is proposed. Generally alum performed somewhat better than iron for turbidity removal and worse for TPC removal. CMD (count mean diameter) is proposed for particle removal index: the higher the TPC removal, the lower the CMD.

Characterization and treatability studies of tannery wastewater using chemically enhanced primary treatment (CEPT)—A case study of Saddiq Leather Works

“…The mixing speeds and times were selected from the experience of similar studies published in the literature [5][6][7][8][9][10][11][12]. A small portion, approximately 20 mL, was wasted to flush out the sampling tube when taking sample from each jar after 30 min of settling [13,14].…”

Experimental investigation of adsorption–flocculation–microfiltration hybrid system in wastewater reuse

“…Adin et al [2] have shown the superiority of ferric chloride (FeCl 3 ) over aluminum sulphate (alum) in flocculating the organic colloids present in the activated sludge effluent. Al-Malack et al [3] have studied the effect of alum, polyaluminium silicate sulfate (PASS) and lime as flocculants on the performance of cross-flow microfiltration of domestic wastewater.…”

Effects of epichlorohydrin–dimethylamine on coagulation and membrane performance of ferric chloride in coagulation–ultrafiltration hybrid process

“…In this way, under acidic condition, charge neutralization between HA molecules (with less negative charges) and FC hydrolysates (more positively charged) would be enhanced. Thus, the demand of FC for would be reduced to achieve the same coagulation effect [30][31][32]. Accordingly, pH 6 was determined to be the optimum pH condition for FC/DAM-ECH coagulation in this study, and its membrane performance in the follow up UF process would also be investigated in comparing with other coagulation methods.…”