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Treatment of domestic wastewater using microbiological processes and hydroponics in Sweden
KTH, School of Biotechnology (BIO).
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Conventional end-of-pipe solutions for wastewater treatment have been criticized from a sustainable view-point, in particular regarding recycling of nutrients. The integration of hydroponic cultivation into a wastewater treatment system has been proposed as an ecological alternative, where nutrients can be removed from the wastewater through plant uptake; however, cultivation of plants in a temperate climate, such as Sweden, implies that additional energy is needed during the colder and darker period. Thus, treatment capacity, additional energy usage and potential value of products are important aspects considering the applicability of hydroponic wastewater treatment in Sweden.

To enable the investigation of hydroponic wastewater treatment, a pilot plant was constructed in a greenhouse located at Överjärva gård, Solna, Sweden. The pilot plant consisted of several steps, including conventional biological processes, hydroponics, algal treatment and sand filters. The system treated around 0.56-0.85 m3 domestic wastewater from the Överjärva gård area per day. The experimental protocol, performed in an average of twice per week over a period of three years, included analysis and measurements of water quality and physical parameters. In addition, two studies were performed when daily samples were analysed during a period of two-three weeks. Furthermore, the removal of pathogens in the system, and the microbial composition in the first hydroponic tank were investigated.

Inflow concentrations were in an average of around 475 mg COD/L, 100 mg Tot-N/L and 12 mg Tot-P/L. The results show that 85-90% of COD was removed in the system. Complete nitrification was achieved in the hydroponic tanks. Denitrification, by means of pre-denitrification, occurred in the first anoxic tank. With a recycle ratio of 2.26, the achieved nitrogen removal in the system was around 72%. Approximately 4% of the removed amount of nitrogen was credited to plant uptake during the active growth period. Phosphorus was removed by adsorption in the anoxic tank and sand filters, natural chemical precipitation in the algal step induced by the high pH, and assimilation in plants, bacteria and algae. The main removal occurred in the algal step. In total, 47% of the amount of phosphorus was removed. Significant recycling of nitrogen and phosphorus through harvested biomass has not been shown. The indicators analysed for pathogen removal showed an achieved effluent quality comparable to, or better than, for conventional secondary treatment. The microbial composition was comparable to other nitrifying biological systems. The most abundant phyla were Betaproteobacteria and Planctomycetes.

In Sweden, a hydroponic system is restricted to greenhouse applications, and the necessary amount of additional energy is related to geographic location. In conclusion, hydroponic systems are not recommended too far north, unless products are identified that will justify the increased energy usage. The potential for hydroponic treatment systems in Sweden lies in small decentralized systems where the greenness of the system and the possible products are considered as advantages for the users.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , iv, 56 p.
Keyword [en]
Microbiology, biological, hydroponics, microbial composition, nitrogen, organic matter, phosphorus, small scale, theoretical energy requirements, wastewater treatment.
Keyword [sv]
Mikrobiologi
National Category
Microbiology
Identifiers
URN: urn:nbn:se:kth:diva-183ISBN: 91-7178-030-0 (print)OAI: oai:DiVA.org:kth-183DiVA: diva2:7835
Public defence
2005-05-18, Oskar Kleins auditorium, AlbaNova, Roslagstullsbacken 21, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20101014Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2010-10-14Bibliographically approved
List of papers
1. A small scale hydroponics wastewater treatment system under Swedish conditions
Open this publication in new window or tab >>A small scale hydroponics wastewater treatment system under Swedish conditions
Show others...
2003 (English)In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 48, no 11, 161-167 p.Article in journal (Refereed) Published
Abstract [en]

A treatment plant using conventional biological treatment combined with hydroponics and microalgae is constructed in a greenhouse in the area of Stockholm, Sweden. The treatment plant is built for research purposes and presently treats 0.559 m(3) of domestic wastewater from the surrounding area per day. The system uses anoxic pre-denitrification followed by aerobic tanks for nitrification and plant growth. A microalgal step further reduces phosphorus, and a final sand filter polishes the water. During a three week period in July 2002 the treatment capacity of this system was evaluated with respect to removal of organic matter, phosphorus and nitrogen. 90% COD removal was obtained early in the system. Nitrification and denitrification was well established with total nitrogen reduction of 72%. Phosphorus was removed by 47% in the process. However, higher phosphorus removal values are expected as the microalgal step will be further developed. The results show that acceptable treatment can be achieved using this kind of system. Further optimisation of the system will lead to clean water as well as valuable plants to be harvested from the nutrient rich wastewater.

Keyword
domestic wastewater, greenhouse, hydroponics, nutrient recovery, small scale treatment
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:kth:diva-5524 (URN)000188094900022 ()2-s2.0-0346008013 (Scopus ID)
Conference
5th International Conference on Small Water and Wastewater Treatment Systems, ISTANBUL, TURKEY, 2002
Note

QC 20100906

Available from: 2006-04-03 Created: 2006-04-03 Last updated: 2017-11-21Bibliographically approved
2. Removal of micro-organisms in a small-scale hydroponics wastewater treatment system
Open this publication in new window or tab >>Removal of micro-organisms in a small-scale hydroponics wastewater treatment system
2005 (English)In: Letters in Applied Microbiology, ISSN 0266-8254, E-ISSN 1472-765X, Vol. 40, no 6, 443-447 p.Article in journal (Refereed) Published
Abstract [en]

Aims: To measure the microbial removal capacity of a small-scale hydroponics wastewater treatment plant. Methods and Results: Paired samples were taken from untreated, partly-treated and treated wastewater and analysed for faecal microbial indicators, i.e. coliforms, Escherichia, coli, enterococci, Clostridium perfringens spores and somatic coliphages, by culture based methods. Escherichia coli was never detected in effluent water after >5.8-log removal. Enterococci, coliforms, spores and coliphages were removed by 4.5, 4.1, 2.3 and 2.5 log respectively. Most of the removal (60-87%) took place in the latter part of the system because of settling, normal inactivation (retention time 12.7 d) and sand filtration. Time-dependent log-linear removal was shown for spores (k = -0.17 log d-1, r2 = 0.99). Conclusions: Hydroponics wastewater treatment removed micro-organisms satisfactorily. Significance and Impact of the Study: Investigations on the microbial removal capacity of hydroponics have only been performed for bacterial indicators. In this study it has been shown that virus and (oo)cyst process indicators were removed and that hydroponics can be an alternative to conventional wastewater treatment.

Keyword
Coliforms, Coliphages, Enterococci, Hydroponics, Removal, Spores, Wastewater treatment
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-5183 (URN)10.1111/j.1472-765X.2005.01689.x (DOI)000202967500009 ()2-s2.0-20044378137 (Scopus ID)
Note
QC 20100928Available from: 2005-05-03 Created: 2005-05-03 Last updated: 2017-12-04Bibliographically approved
3. Theoretical energy requirements for maintenance of green plants in hydroponic wastewater treatment.
Open this publication in new window or tab >>Theoretical energy requirements for maintenance of green plants in hydroponic wastewater treatment.
2004 (English)In: Vatten, ISSN 0042-2886, no 3, 187-191 p.Article in journal (Other academic) Published
Abstract [en]

Hydroponic wastewater treatment takes advantage of the nutrient removing capacity of green plants. In addition to the nutrient assimilation, the roots provide a growth substrate for microorganisms involved in the biological treatment processes. However, to maintain year-round performance by the plants, additional energy muse be provided at higher latitudes, even if the hydroponics are situated in a greenhouse. To evaluate the energy demand by hydroponics in Sweden, two theoretical operational conditions have been compared. These conditions were based on A: requirements by winter resting plants, 10°C and 400 lux 16 h day-1, and B: good growth. 20°C and 2000 lux 16 h day-1. Further, five Swedish cities at different latitudes and their respective demands to reach the two conditions were compared. These cities were Lund (55°72' N), Visbv (57°38' N) Stockholm (59°35’ N), Ostersund (63°20’ N) and Kiruna (67°83’ N). The calculations showed that under Swedish conditions, the extra heat demand always exceeds the light demand on a yearlv basis except for the high temperature and light standard in Lund. The yearly light requirements are similar for the five cities, whereas the heat energy displays strong latitude dependence, e.g. the yearly heat demand in Kiruna is almost seven times higher than in Lund to reach an average indoor temperature of 10°C.

Keyword
energy, greenhouse, heat, hydroponics, latitude, light, wastewater treatment.
National Category
Microbiology
Identifiers
urn:nbn:se:kth:diva-25258 (URN)
Note
QC 20101014Available from: 2010-10-14 Created: 2010-10-14 Last updated: 2010-10-14Bibliographically approved
4. A comparative study of six hydroponic wastewater treatment plants.
Open this publication in new window or tab >>A comparative study of six hydroponic wastewater treatment plants.
2005 (English)In: Vatten, ISSN 0042-2886, no 2, 95-104 p.Article in journal (Other academic) Published
Abstract [en]

During the last two decades, wastewater treatment in systems combining conventional biological processes andhydroponics has been tried at several locations. In this article, six different systems are described and theirtreatment results compared. Five systems were found in literature, and the sixth system was constructed andoperated by the microbiology group at KTH. These systems can be divided into three subgroups: i) demonstrationsystems with small inflow and long hydraulic retention time (HRT), ii) pilot systems with small to moderateinflow and moderate HRT, iii) full scale systems with large inflow and short HRT. In general, removalof organic matter seems to be most efficient in systems resembling an active sludge process. Systems with longHRT appears over-dimensioned as long as the volume is not simultaneously used for treatment and production.Nitrogen was efficiently removed through conventional biological processes, whereas phosphorus removalthrough mainly sedimentation and adsorption in the systems was not very efficient. Nutrient removal bymeans of up-take through plant growth has not contributed significantly in any of the described treatmentsystems. None of the treatment plants have had the primary objective of biomass production. Hence, potentialremoval and recycling of nutrients through a productive system still remains to be answered.

Keyword
wastewater treatment, hydroponics, BOD, nitrogen, phosphorus, greenhouse
National Category
Microbiology in the medical area
Identifiers
urn:nbn:se:kth:diva-25259 (URN)
Note
QC 20101014Available from: 2010-10-14 Created: 2010-10-14 Last updated: 2010-10-14Bibliographically approved
5. Energy savings versus year‐round production in a small hydroponic system for wastewater treatment.
Open this publication in new window or tab >>Energy savings versus year‐round production in a small hydroponic system for wastewater treatment.
(English)In: Water Science and Technology, ISSN 0273-1223Article in journal (Other academic) Submitted
National Category
Microbiology in the medical area
Identifiers
urn:nbn:se:kth:diva-25262 (URN)
Note
QS 20120328Available from: 2010-10-14 Created: 2010-10-14 Last updated: 2012-03-28Bibliographically approved
6. Investigation of the microbial composition in the hydroponic step of a treatment system for domestic wastewater with fluorescent in situ hybridization (FISH).
Open this publication in new window or tab >>Investigation of the microbial composition in the hydroponic step of a treatment system for domestic wastewater with fluorescent in situ hybridization (FISH).
(English)In: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574Article in journal (Other academic) Submitted
National Category
Microbiology in the medical area
Identifiers
urn:nbn:se:kth:diva-25263 (URN)
Note
QS 20120328Available from: 2010-10-14 Created: 2010-10-14 Last updated: 2012-03-28Bibliographically approved

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