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Removal of metals and hydrocarbons from urban snowmelt by coagulation and flocculation
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten. (Urban Water Engineering)ORCID-id: 0000-0003-3580-8715
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten. (Urban Water Engineering)
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.ORCID-id: 0000-0001-9541-3542
Visa övriga samt affilieringar
(Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
Abstract [en]

The treatment efficiency of a coagulation/flocculation and sedimentation process was investigated in urban snowmelt. Five different coagulants were evaluated for their effectiveness in reduction of particle content, organic carbon, total and dissolved metals, hydrocarbon oil index, PAHs and if any changes occurred in the particle size distribution. The pollutants in the snow melt were mostly in the particulate phase, and for both oil index and PAHs characterized by the larger sized molecules. An iron chloride coagulant was the only coagulant that had an effect on the particle size distribution post-treatment, where the distribution was shifted towards larger particles. In terms of total metal removal, the performance for the coagulants were similar with above 90% removal on average. Dissolved Cu, was one of the metals found in the dissolved phase, and it was reduced by 40% by coagulation treatment. The iron chloride coagulant did increase the dissolved Zn, attributed to a larger drop in pH resulting in a higher ion mobility. Similarly, the reduction in organic content, both TOC/oil/PAH were above 90% for most coagulants.

Nyckelord [en]
Stormwater treatment, pollutant removal, treatment efficiency
Nationell ämneskategori
Vattenteknik
Forskningsämne
VA-teknik
Identifikatorer
URN: urn:nbn:se:ltu:diva-73089OAI: oai:DiVA.org:ltu-73089DiVA, id: diva2:1292994
Tillgänglig från: 2019-03-01 Skapad: 2019-03-01 Senast uppdaterad: 2019-03-01
Ingår i avhandling
1. Coagulation process characteristics and pollutant removal from urban runoff
Öppna denna publikation i ny flik eller fönster >>Coagulation process characteristics and pollutant removal from urban runoff
2019 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Luleå: Luleå University of Technology, 2019
Serie
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Nyckelord
stormwater, urban snowmelt, road runoff, coagulation/flocculation/sedimentation, coagulation characteristics, coagulation mechanism, treatment efficiency
Nationell ämneskategori
Vattenteknik
Forskningsämne
VA-teknik
Identifikatorer
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 (Engelska)
Opponent
Handledare
Tillgänglig från: 2019-03-04 Skapad: 2019-03-01 Senast uppdaterad: 2019-04-09Bibliografiskt granskad

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Herrmann, IngaHedström, AnnelieViklander, Maria

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Nyström, FredrikHerrmann, IngaHedström, AnnelieViklander, Maria
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