Laboratory scale evaluation of coagulants for treatment of stormwater

• Published in: Journal of water process engineering Vol. 36; p. 101271
• Main Authors: Nyström, Fredrik, Nordqvist, Kerstin, Herrmann, Inga, Hedström, Annelie, Viklander, Maria
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2020
• Subjects: Centre - Centre for Stormwater Management (DRIZZLE); Centrumbildning - Centrum för dagvattenhantering (DRIZZLE); Charge neutralization; Coagulation mechanism; Stormwater; Sweep floc; Treatment; Urban Water Engineering; VA-teknik; Zeta potential; Charge neutralization; Treatment; Sweep floc; Stormwater; Coagulation mechanism; Zeta potential
• ISSN: 2214-7144; 2214-7144
• DOI: 10.1016/j.jwpe.2020.101271

•Stormwater particle content greatly reduced with coagulation/flocculation treatment.•Pre-hydrolyzed coagulants more favorable for treatment of low alkalinity stormwater.•Stoichiometric charge neutralization was the dominant coagulation mechanism. The treatment effect and process characteristics of coagulation were investigated in semi-synthetic stormwater in laboratory-scale using jar tests. An initial screening of twelve coagulants and flocculant aids was carried out to find a selection of chemicals that efficiently reduced turbidity and suspended solids. Five coagulants were then further investigated with additional parameters measured (conductivity, alkalinity, and ζ-potential). The semi-synthetic stormwater was characterized by a high but variable, particle content, and low alkalinity. In the jar tests, a high treatment efficiency (>90 % reduction of both turbidity and suspended solids) was achieved for all coagulants. For very low alkalinity waters, the use of a biopolymer such as chitosan may be advantageous due to minimal alkalinity consumption. Based on the occurrence of charge reversal for all chemicals investigated, the mechanism for coagulation was likely charge neutralization. Treatment effect occurred in the ζ-potential span of -14 to +1 mV depending on the coagulant used. Initial turbidity and the ζ-potential are interesting parameter candidates for dosing control in stormwater treatment applications.