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Treatment of road runoff by coagulation/flocculation and sedimentation
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.ORCID iD: 0000-0003-3580-8715
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.ORCID iD: 0000-0003-0520-796x
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.ORCID iD: 0000-0001-9541-3542
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2019 (English)In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 79, no 3, p. 518-525Article in journal (Refereed) Published
Abstract [en]

A laboratory investigation of the treatment potential of a coagulation process in the context of stormwater treatment was undertaken. The initial 25 L road runoff generated from four rain events was collected and subjected to a jar-testing regime with two commercial coagulants. The treatment effect was assessed by analysing the runoff before and after treatment for turbidity, suspended solids and metal content. The coagulation process resulted in particle and total metal reduction of more than 90% compared to 40% for only sedimentation. Up to 40% reduction of dissolved Cr, Cu and Pb was also observed compared to 0% for sedimentation. This study shows that coagulation may be a useful process for stormwater treatment systems when the treatment requirements are high.

Place, publisher, year, edition, pages
IWA Publishing, 2019. Vol. 79, no 3, p. 518-525
Keywords [en]
advanced stormwater treatment, coagulation, metals, particles, road runoff, suspended solids
National Category
Water Engineering
Research subject
Urban Water Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-73090DOI: 10.2166/wst.2019.079PubMedID: 30924806Scopus ID: 2-s2.0-85063686388OAI: oai:DiVA.org:ltu-73090DiVA, id: diva2:1292997
Funder
Swedish Research Council Formas, 2016-20075Swedish Research Council Formas, 2016-01447
Note

Validerad;2019;Nivå 2;2019-04-08 (oliekm)

Available from: 2019-03-01 Created: 2019-03-01 Last updated: 2019-08-16Bibliographically approved
In thesis
1. Coagulation process characteristics and pollutant removal from urban runoff
Open this publication in new window or tab >>Coagulation process characteristics and pollutant removal from urban runoff
2019 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Many different stormwater control measures (SCMs) can be implemented in order to mitigate issues with polluted stormwater flows into receiving water bodies.  The treatment function of  SCMs is commonly based on the removal of particles by sedimentation, thereby also removing pollutants associated with particles. In recent years, more attention has been given to characterizing and understanding of different particle size fractions and their association with pollutants commonly found in stormwater. It has become increasingly clear that the smaller sized particles are very important pollutant transporters and should be considered when designing and implementing SCMs. However, the settling velocities for smaller sized particles are very low and may not be effectively removed in existing SCMs. One treatment process with a proven ability to enhance sedimentation is coagulation/flocculation, widespread in water and wastewater treatment, but with very few accounts of it being used in a stormwater context. This thesis aims to investigate the treatability of stormwater with a coagulation/flocculation process. This includes the determination of operating conditions, the dominating coagulation mechanism and the reduction efficiency of stormwater related pollutants. The objectives of the thesis were achieved in laboratory tests treating stormwater in a jar-testing procedure.

An initial screening of primary coagulants and flocculant aids was conducted using an urban snowmelt mixture. Five of the chemicals were then selected for an extended testing regime which was setup up to determine the operating conditions where maximal turbidity reduction was attained by measuring the pH, conductivity, alkalinity and zeta-potential over the tested doses for each coagulant. Criteria used for chemical selection included high turbidity reduction, low dose requirement and low pH/alkalinity impacts.

Charge reversal was observed at positive zeta-potential indicating that the dominating coagulation mechanism was charge neutralization. The content of turbidity/total suspended solids, total organic carbon, total metals and hydrocarbons by >90%. Dissolved copper was reduced by 40% on average, and the reduction rates for dissolved zinc were varying with up to a 300% increase, presumably due to changes in pH, leading to a higher mobility. Changes in the particle size distribution after coagulation/flocculation as compared to sedimentation indicated an effect on the size fraction corresponding to smaller particles.

The performance of the coagulation/flocculation process was also tested on road runoff collected from a central road in Luleå with a high traffic intensity. Two coagulants were tested, iron chloride and pre-hydrolyzed aluminum chloride. Reduction rates for the total metal fraction were >90% on average for both coagulants, but for the dissolved metal fractions differences could be observed between the coagulants with the iron chloride resulting in higher reductions for dissolved chrome (57% compared to 34%) and copper (47% compared to 30%). Both products increased the dissolved fractions of nickel and zinc due to lower final pH.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keywords
stormwater, urban snowmelt, road runoff, coagulation/flocculation/sedimentation, coagulation characteristics, coagulation mechanism, treatment efficiency
National Category
Water Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-73091 (URN)978-91-7790-322-2 (ISBN)978-91-7790-323-9 (ISBN)
Presentation
2019-04-26, F231, VR-Studion, Laboratorievägen 10, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2019-03-04 Created: 2019-03-01 Last updated: 2019-04-09Bibliographically approved

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Herrmann, IngaHedström, AnnelieViklander, Maria

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