liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Impact of loads, season, and plant species on the performance of a tropical constructed wetland polishing effluent from sugar factory stabilization ponds
Linköping University, Department of Physics, Chemistry and Biology, Ecology. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Ecology. Linköping University, The Institute of Technology.
2007 (English)In: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574, E-ISSN 1872-6992, Vol. 29, no 1, 66-76 p.Article in journal (Refereed) Published
Abstract [en]

The effects of wastewater loading rates and two macrophyte species on treatment of sugar factory stabilization pond effluent were investigated in a pilot-scale free water surface constructed wetland (FWS CW) system in western Kenya. For 12 months, four CWs were operated at a hydraulic loading rate of 75 mm day−1 and four at 225 mm day−1. Half the CWs were planted with Cyperus papyrus and half with Echinochloa pyramidalis. Water samples were taken at the inlets and outlets and analyzed for TP, TDP, NH4-N, and TSS. Mass removal rates of the selected water quality parameters were compared during three periods designated the short rain (period 1), dry (period 2), and long rain (period 3) seasons. There was a significant linear relationship between the mass removal rate of TP, NH4-N, and TSS and the mass load, and season had a significant effect on the mass removal rate of TSS, NH4-N, and TDP. Mass loading rates for TDP were about 78% of those for TP, whereas TDP comprised 78–99% of TP mass outflow rates, indicating a release of dissolved P within the CWs. The only significant difference between the two macrophyte species was associated with mass removal of NH4-N, with more efficient removal in CWs planted with C. papyrus than those with E. pyramidalis. TP mass removal rates were 50–80% higher when a mean water loss for CWs 6–8 during periods 1 and 2 was assumed to represent evapotranspiration for all CWs in period 3 instead of pan evaporation data. This illustrated the importance of accurate estimations of evapotranspiration for pollutant mass removal rates in CWs in tropical climates.

Place, publisher, year, edition, pages
2007. Vol. 29, no 1, 66-76 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-39668DOI: 10.1016/j.ecoleng.2006.07.015ISI: 000243600700008Local ID: 50668OAI: oai:DiVA.org:liu-39668DiVA: diva2:260517
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
In thesis
1. Wastewater treatment in constructed wetlands: Effects of vegetation, hydraulics and data analysis methods
Open this publication in new window or tab >>Wastewater treatment in constructed wetlands: Effects of vegetation, hydraulics and data analysis methods
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Degradation of water resources has become one of the most pressing global concerns currently facing mankind. Constructed Wetlands (CWs) represent a concept to combat deterioration of water resources by acting as buffers between wastewater and receiving water bodies. Still, constructing wetlands for the sole purpose of wastewater treatment is a challenging task. To contribute to this research area, the fundamental question raised in this doctorate thesis was: how do factors such as vegetation and residing water movements (hydraulics) influence wastewater treatment in CWs? Also, effects of different data analysis methods for results of CW hydraulics and wastewater treatment were investigated. Research was focused on  phosphorus (P), ammonium-nitrogen (NH4+-N) and solids (TSS) in wastewater and o n P in macrophyte biomass. Studies were performed in pilot-scale free water surface (FWS) CW systems in Kenya (Chemelil) and Sweden (Halmstad) and as computer simulations.

Results from the Chemelil CWs demonstrated that meeting effluent concentration standards simultaneously for all water quality parameters in one CW was difficult. Vegetation harvest, and thus nutrient uptake by young growing macrophytes, was important for maintaining low effluents of NH4+-N and P, especially during dry seasons. On the other hand, mature and dense vegetation growing for at least 4 months secured meeting TSS standards. Phosphorus in above-ground green biomass accounted for almost 1/3 of the total P mass removal, demonstrating high potential for P removal through macrophyte harvest in CWs. Also, results suggested that harvest should be species-specific to achieve high P removal by macrophytes and overall acceptable wastewater treatment in CWs. Still, different methods to estimate evapotranspiration (ET) from the Chemelil CWs showed that water balance calculations greatly impacted estimations of wastewater treatment results.

Hydraulic tracer studies performed in the Chemelil and Halmstad CWs showed that mature and dense emergent vegetation in CWs could reduce effective treatment volumes (e-values), which emphasized the importance of regulating this type of vegetation. Also, it was shown that hydraulic tracer studies with lithium chloride performed in CWs with dense emergent vegetation had problems with low tracer recoveries. This problem could be reduced by promoting the distribution of incoming tracer solution into the CW using a barrier near the CW inlet pipe. Computer simulation results showed that the choice of tracer data analysis method greatly influenced quantifications of CW hydraulics and pollutant removal. The e-value could be 50% higher and the pollutant removal 13% higher depending upon used method. Moreover, unrealistic evalues (above 100%) in published literature could to some extent be explained by tracer data analysis method. Hence, to obtain more reliable hydraulic data and wastewater treatment results from CWs, more attention should be paid to the choice of tracer data analysis method.

Abstract [sv]

Konstruerade våtmarker representerar ett koncept för möjligheten att nå en hållbar vattenresurshantering genom att agera som ”filter” mellan föroreningskälla och viktiga vattenresurser såsom sjöar och hav. Mycket kunskap saknas däremot om hur man konstruerar våtmarker med en optimal och pålitlig vattenreningskapacitet. Den här avhandlingen undersöker därför hur vegetation och vattnets väg genom våtmarken (hydrauliken) påverkar avloppsvattenrening i våtmarker. Dessutom undersöktes hur valet av dataanalysmetod av insamlad data påverkar resultaten. Studier genomfördes i Kenya och Sverige i experimentvåtmarker (ca. 40-60 m2) och inkluderadedatainsamling av vattenkvalité, hydraulik (spårämnesexperiment) samt biomassa och fosfor i biomassan av två olika våtmarksväxter. Dessutom genomfördes datorsimuleringar.

Resultaten från Kenya visade att växtskörd och efterföljande näringsupptag av nyskördade växter var viktig för att uppnå låga utgående koncentrationer av fosfor och ammonium i en tropisk våtmark, speciellt under torrsäsongen. Däremot var en välutvecklad och tät vegetation viktig för reningen av partiklar. Fosfor i grön växtbiomassa representerade cirka 1/3 av våtmarkernas totala fosforrening, vilket påvisade potentialen i att genom skörd ta bort fosfor från avloppsvatten m.h.a. konstruerade våtmarker. Resultaten pekade också på att skörden bör vara art-specifik för att uppnå en hög fosforrening och generellt bra vattenreningsresultat. Dock visade olika beräkningsmetoder att vattenbalansen i en tropisk våtmark markant kan påverka vattenreningsresultaten.

Resultaten från spårämnesexperimenten demonstrerade att den effektiva våtmarksvolymen för vattenrening blev mindre vid hög täthet av övervattensväxter. Detta pekade på att regelbunden växtskörd var viktig för att uppnå god vattenrening i våtmarker. Experiment med spårämnet litium visade att man kan få felaktiga resultat p.g.a. att en del spårämne fasthålls på botten i våtmarken om denna har mycket övervattensväxter. Därför bör spridningen av spårämnet i sådana våtmarker underlättas m.h.a. en spridningsbarriär nära inloppsröret. Simuleringar visade också att valet av dataanalysmetod av spårämnesdata starkt kan påverka resultaten och därmed också vår tolkning av en våtmarks hydraulik och reningskapacitet. Den effektiva volymen kunde vara 50% högre och reningseffekten 13% högre beroende på vilken metod som användes. Likaså kan valet av dataanalysmetod ha bidragit till överskattade och orealistiska effektiva volymer (över 100%) i artiklar publicerade de senaste 25 åren. Genom att fokusera mer på valet av dataanalysmetod och t.ex. jämföra resultaten från två olika metoder kan man minimera risken för bristfälliga resultat och därmed felaktiga slutsatser om en våtmarks vattenreningskapacitet.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 59 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1509
Keyword
constructed wetland, free water surface flow, wastewater treatment, Kenya, Sweden, vegetation, harvest, Cyperus papyrus, Echinochloa pyramidalis, mass load, phosphorus, ammonium, suspended solids, pollutant removal, hydraulics, residence time distribution, data analysis methods, Konstgjorda våtmarker, avloppsvatten, vattenrening, fosfor, ammonium, partiklar, Kenya, Sverige, växter, Cyperus papyrus, Echinochloa pyramidalis, skörd, hydraulik, dataanalysmetod
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-91402 (URN)978-91-7519-649-7 (ISBN)
Public defence
2013-05-30, Planck, Physics House, Campus Valla, Linköpings universitet, Linköping, 13:00 (English)
Opponent
Supervisors
Available from: 2013-04-24 Created: 2013-04-24 Last updated: 2014-10-08Bibliographically approved
2. Treatment wetlands in a tropical climate
Open this publication in new window or tab >>Treatment wetlands in a tropical climate
2006 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The decrease of water resources values as a result of eutrophication is a major problem in numerous lakes around the world, including the Great African Lakes. One of the most important tasks to limit this eutrophication, is to decrease the nutrient input from land-based activities. In the catchment area of Lake Victoria, industries such as sugar factories have been identified as being responsible for a large part of the increased nutrient flow to rivers and lakes. Constructed wetlands (CW) have been suggested as a low-cost method to improve the current wastewater treatment, commonly consisting of stabilization ponds. The aim of this thesis was to explore and quantify the effect of mass loading rates and two macrophyte species on treatment performance of free water surface (FWS) CWs polishing sugar factory effluent, with a special focus on phosphorus (P) removal. Also, another objective was to evaluate the amount of P that could be removed by harvesting the emergent macrophytes. The studies were performed in a pilot-scale FWS CW system in western Kenya. Four CWs were operated at a low loading rate and four at a high one, and half the CWs were planted with Cyperus papyrus and half with Echinochloa pyramidalis. Methods included field and laboratory measurements, and mass balance calculations. Water fow measurements and a rough chloride balance indicated relatively large water leakages through the banks and/or to the groundwater. Various estimates of the evapotranspiration (ET) were evaluated, and finally ET was estimated from pan evaporation data using a coefficient of 1.4, resulting in a mean ET of 8 mm day-1 for the whole study period.

The mass removal (g m-2 day-1) of total P (TP), total particulate P (TPP), ammoniumnitrogen (NH4+-N) and total suspended solids (TSS), was significantly and positively correlated with the respective mass loads to the CWs. Also, season had a significant effect on the mass removal of TDP, TSS, and NH4+-N, with increasing removal as the study progressed for the two former and a decreasing removal for the latter parameter. Results also showed that the removal of TP (0. 15-0.23 g m-2 day-1) by the studied CW systems were in the higher range of P removal rates for temperate FWS wetland systems, indicating a high potential of high-load tropical FWS CW to remove P from wastewater. The relative reduction of mass load varied between 20 to 57% for TP, 1.4 to 70% for total dissolved solids (TDP), 24 to 86% for NH4+-N and 32 to 73% for TSS, and was generally lower at higher mass loads. The only significant difference between the two macrophyte species was associated with area-specific mass removal of NH4+-N, with C. papyrus CWs having twice as high removal as those with E. pyramidalis. However, when the ET for the CWs was calculated in a different way, this relationship became insignificant. These results showed that conclusions about treatment performance of tropical CWs are strongly influenced by the accuracy of the water balance.

High relative reduction of TSS mass load, but low reduction of both TDP and NH4+-N were observed when the macrophytes had been growing for at least 5 months, whilethe opposite was observed when the macrophyte shoots were around I month old.This suggested that macrophytes were important for the dynamics of TDP, NH4+-N and TSS removal, possibly through uptake of dissolved ions, and influences onsedimentation/resuspension processes.

The P recovered in the above-ground green parts of the harvested macrophytes (0.03-0.06 g m-2 day-1) was in the higher range of values reported from CWs in temperate regions, suggesting a higher potential for nutrient recovery by macrophytes in tropical wetlands than in temperate ones. Also, P stored in the harvested green biomass of the macrophytes represented roughly 20-28% and 25-100% of the daily mass removal of TP and TDP by the CWs, respectively, indicating the important function of plants as nutrient traps. Similar tissue P concentrations were found in each macrophyte species independent of mass load, suggesting excess available P in the CWs. However, the biomass of C. papyrus, and the standing stock of P, responded positively to an increase in nutrient load. This was not observed for E. pyramidalis, suggesting that species specific harvest strategies should be used in order to attain high nutrient storage and a crop of good fodder quality.

General management strategies that could be beneficial not only from an optimal plant quality perspective, but also from a water quality point of view, include more frequent harvests (suggested < 4 months intervals), and leaving part of the wetland intact at each harvest event. Shorter harvest intervals would also minimize macrophyte tissue losses to senescence and decomposition. This would result in better conservation of biomass resources for the local communities.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2006. 47 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1273
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-38660 (URN)45250 (Local ID)91-85643-79-3 (ISBN)45250 (Archive number)45250 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2013-12-17

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Bojcevska, HristinaSundblad-Tonderski, Karin

Search in DiVA

By author/editor
Bojcevska, HristinaSundblad-Tonderski, Karin
By organisation
EcologyThe Institute of Technology
In the same journal
Ecological Engineering: The Journal of Ecotechnology
Natural Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 321 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf