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Coagulation process characteristics and pollutant removal from urban runoff
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.ORCID-id: 0000-0003-3580-8715
2019 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Luleå: Luleå University of Technology, 2019.
Serie
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Emneord [en]
stormwater, urban snowmelt, road runoff, coagulation/flocculation/sedimentation, coagulation characteristics, coagulation mechanism, treatment efficiency
HSV kategori
Forskningsprogram
VA-teknik; Centrumbildning - Centrum för dagvattenhantering (DRIZZLE)
Identifikatorer
URN: urn:nbn:se:ltu:diva-73091ISBN: 978-91-7790-322-2 (tryckt)ISBN: 978-91-7790-323-9 (digital)OAI: oai:DiVA.org:ltu-73091DiVA, id: diva2:1293005
Presentation
2019-04-26, F231, VR-Studion, Laboratorievägen 10, Luleå, 09:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2019-03-04 Laget: 2019-03-01 Sist oppdatert: 2023-09-05bibliografisk kontrollert
Delarbeid
1. Laboratory scale evaluation of coagulants for treatment of stormwater
Åpne denne publikasjonen i ny fane eller vindu >>Laboratory scale evaluation of coagulants for treatment of stormwater
Vise andre…
2020 (engelsk)Inngår i: Journal of Water Process Engineering, E-ISSN 2214-7144, Vol. 36, artikkel-id 101271Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

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.

sted, utgiver, år, opplag, sider
Elsevier, 2020
Emneord
Stormwater, treatment, coagulation mechanism, sweep floc, charge neutralization, zeta potential
HSV kategori
Forskningsprogram
VA-teknik; Centrumbildning - Centrum för dagvattenhantering (DRIZZLE)
Identifikatorer
urn:nbn:se:ltu:diva-73088 (URN)10.1016/j.jwpe.2020.101271 (DOI)000542174000021 ()2-s2.0-85083768623 (Scopus ID)
Merknad

Validerad;2020;Nivå 2;2020-04-29 (alebob)

Tilgjengelig fra: 2019-03-01 Laget: 2019-03-01 Sist oppdatert: 2023-09-05bibliografisk kontrollert
2. Removal of metals and hydrocarbons from urban snowmelt by coagulation and flocculation
Åpne denne publikasjonen i ny fane eller vindu >>Removal of metals and hydrocarbons from urban snowmelt by coagulation and flocculation
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(engelsk)Manuskript (preprint) (Annet vitenskapelig)
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.

Emneord
Stormwater treatment, pollutant removal, treatment efficiency
HSV kategori
Forskningsprogram
VA-teknik
Identifikatorer
urn:nbn:se:ltu:diva-73089 (URN)
Tilgjengelig fra: 2019-03-01 Laget: 2019-03-01 Sist oppdatert: 2023-09-05
3. Treatment of road runoff by coagulation/flocculation and sedimentation
Åpne denne publikasjonen i ny fane eller vindu >>Treatment of road runoff by coagulation/flocculation and sedimentation
Vise andre…
2019 (engelsk)Inngår i: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 79, nr 3, s. 518-525Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
IWA Publishing, 2019
Emneord
advanced stormwater treatment, coagulation, metals, particles, road runoff, suspended solids
HSV kategori
Forskningsprogram
VA-teknik; Centrumbildning - Centrum för dagvattenhantering (DRIZZLE)
Identifikatorer
urn:nbn:se:ltu:diva-73090 (URN)10.2166/wst.2019.079 (DOI)000462917700011 ()30924806 (PubMedID)2-s2.0-85063686388 (Scopus ID)
Forskningsfinansiär
Swedish Research Council Formas, 2016-20075Swedish Research Council Formas, 2016-01447
Merknad

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

Tilgjengelig fra: 2019-03-01 Laget: 2019-03-01 Sist oppdatert: 2023-09-05bibliografisk kontrollert

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