Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Energiebesparing door lokale verwarming : test op teelttafels bij Elstgeest Potplanten
Raaphorst, Marcel ; Noort, Filip van - \ 2017
Bleiswijk : Wageningen University & Research, BU Glastuinbouw (Rapport GTB 1439) - 18
kasgewassen - glastuinbouw - kassen - dieffenbachia - potplanten - sierplanten - verwarming - verwarmingssystemen - energiebesparing - greenhouse crops - greenhouse horticulture - greenhouses - pot plants - ornamental plants - heating - heating systems - energy saving
On a pot plant nursery three cultivation tables are heated directly with mat heating and one cultivation table is heated indirectly with tube heating. At these four tables the effect is measured on the air temperature below the table, the pot temperature, the energy use and the crop growth of Dieffenbachia. The conclusion is, that with mat heating a lower air temperature can be held under cultivation table to achieve a certain pot temperature. It is estimated that with this lower air temperature 10-30% of heat is saved because less heat disappears to the soil. For Dieffenbachia, the greenhouse air temperature above the pot is more determining for crop development than the pot temperature is. It is expected, that the energy-saving effect of mat heating is larger for plants with a low growth point, for which the pot temperature has more effect on growth.
Systeemstap naar minimaal energieverbruik Alstroemeria : metingen op praktijkbedrijven en een energiezuinige teeltconcept
Garcia Victoria, N. ; Zwart, Feije de; Weel, Peter van; Steenhuizen, Johan ; Groot, Marco de - \ 2017
Bleiswijk : Wageningen University & Research, BU Glastuinbouw (Rapport GTB 1372) - 66
kasgewassen - glastuinbouw - kastechniek - kassen - alstroemeria - energiebehoeften - energiebesparing - verwarming - aanvullend licht - kunstlicht - simulatiemodellen - isolatie (insulation) - evaporatie - greenhouse crops - greenhouse horticulture - greenhouse technology - greenhouses - energy requirements - energy saving - heating - supplementary light - artificial light - simulation models - insulation - evaporation
Alstroemeria cultivation in The Netherlands requires energy for heating, supplementary light and root cooling. For the program “Greenhouse as Source of Energy” we calculated to which extent the energy demand for growing this crop can be reduced with existing energy saving innovations. Some innovations were tested in practice, others were calculated by means of the greenhouse climate simulation model Kaspro. Results showed that it is possible to save up to 34% energy for heating compared to the reference situation. 40% energy can be saved on electricity for supplementary light and root cooling. However, this strategy leads to a reduced amount of PAR-light in the winter, and 4% less flowers in comparison with the reference. The greatest impact can be achieved by increasing the insulation of the greenhouse by using double screens, reducing the evaporation from the soil, improving the crop hygiene to avoid extra evaporation from crop debris and reduce pest pressure, and implementing controlled dehumidification of the greenhouse air.
Paprikateelt in de hooggeïsoleerde VenLow Energy kas
Zwart, H.F. de; Gelder, A. de; Hofland-Zijlstra, J. ; Noordam, M. - \ 2017
Bleiswijk : Wageningen University & Research, BU Glastuinbouw (Rapport GTB 1435) - 34
paprika's - capsicum annuum - kassen - kasgewassen - glasgroenten - glastuinbouw - energiebesparing - energiegebruik - isolatie (insulation) - broeikasgassen - kooldioxide - sweet peppers - greenhouses - greenhouse crops - greenhouse vegetables - greenhouse horticulture - energy saving - energy consumption - insulation - greenhouse gases - carbon dioxide
In order to realise a horticultural sector that operates without the combustion of fossil fuel, the first step is to reduce the demand for heating by improving the insultation of greenhouses. This holds especially for crops that are grown at high temperatures, like sweet pepper. The Venlow Energy greenhouse with its double glass cladding and energy screen is a good example of such a highly insulated greenhouse. This report presents the results of a one year cultivation and serves as a bench mark for the state of the art in energy conserving production of Sweet Pepper in the Netherlands. It shows the greenhouse climate conditions required, and the possibilities to meet these requirements with a low energy consumption and options to realise this from sustainable sources. The application of sustainable energy sources was not tested in practice, but since the exact resources (heat and CO2) required from hour to hour were measured, it is easy to do the math on the amounts and capacities needed. The application of pure CO2 or CO2 from another sustainable source is essential when aiming at a fossil energy free horticulture. Without external CO2 the production will drop substantially, especially because an energy conserving greenhouse has typically a strongly reduced air exchange. But, for the same reason, the amount of CO2 needed to increase the CO2 concentration is quite limited, 25 kg/m² per year in this experiment. With a production of 32.5 kg class I of red Sweet Pepper per m², the experiment has shown that halving the energy consumption compared to the general practice did’nt reduced the production.
Vochtbeheersing in kassen en terugwinning van latente energie : Een verkenning naar vochtbeheersing in kassen en de mogelijkheden van het terugwinnen van de energie die opgesloten zit in de gewasverdamping
Weel, P.A. van; Zwart, H.F. de; Voogt, J.O. - \ 2016
Wageningen UR Gastuinbouw (Rapport GTB 1421) - 76 p.
kassen - kastechniek - tomaten - glastuinbouw - ontvochtiging - energiegebruik - energiebesparing - ventilatie - greenhouses - greenhouse technology - tomatoes - greenhouse horticulture - dehumidification - energy consumption - energy saving - ventilation
Dehumidification of a greenhouse by ventilation increases the energy input with 8-10 m3/m2.year of natural gas to compensate the heat losses. This study shows different methods to reduce those energy losses. A 25% reduction in ventilation is obtained by using heat exchangers connected to plastic distribution ducts or by using the Ventilationjet system. The sensible heat from the exhaust air can be used to heat the incoming outside air to greenhouse temperature. Heat exchangers with 100% efficiency to do that are available. The latent heat included in the water vapour leaving the greenhouse can be recovered by means of a condensating wall. A good working priciple is the Dewpoint Heat Exchanger in which outside air is wettened to reach the lowest possible temperature and then used to cool down the greenhouse air far below the temperature where condensation begins. The recovered latent heat must be stored in a water tank to use it in the heating pipes. Another approach is to skip ventilation and use a set of a cold and warm heat exchanger connected to a heat pump or to use a salt water absorber. The absorber opens the possibility to use solar or wind energy to dehumidify the greenhouse and collect 100% of the sensible and latent heat.
Kokos als volvelds groeimedium geeft beste resultaten bij lisianthus
Raaphorst, Marcel - \ 2016
horticulture - greenhouse horticulture - cut flowers - eustoma grandiflorum - substrates - cultural methods - copra - agricultural research - growing media - energy saving - environmental protection - fertilizer application - water use
Het Nieuwe Gewas : sturen van de plantvorm voor verhoogde lichtbenutting
Gelder, Arie de; Janse, Jan ; Warmenhoven, Mary - \ 2016
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1407) - 62
tomaten - solanum lycopersicum - kasgewassen - glasgroenten - glastuinbouw - energiebesparing - plantenontwikkeling - gewasteelt - licht - tomatoes - greenhouse crops - greenhouse vegetables - greenhouse horticulture - energy saving - plant development - crop management - light
Wageningen UR Greenhouse horticulture searched in the “The New Crop” project for the crop structure that best contributes to the goal of energy-efficient production and therefore energy saving, by removing 33, 44 or 55% of the leaves at a young stage. On October 10th 2014 the experiment started with topped plants of the tomato variety Brioso grafted on Maxifort. Dry matter production was lowest in the very open crop, however partitioning to the fruits was highest in that treatment. Therefore, this crop produced in the winter under assimilation lighting most. In summer, the standard treatment was the best and the production in this treatment was highest. The plants in the very open treatment were shorter and had smaller leaves than the plants of the standard treatment. This is might be due to a different red: far red ratio of light in the crop. Leaf picking at a young stage contributes to better distribution of assimilates to the fruits. This can be used as a crop management measure as the plant in winter develops too much leaves. The project was funded by the Dutch energy transition program “Kas als Energiebron”.
Green Business Benefits : analyse van natuurpraktijken door Nederlandse bedrijven
Vreke, Jan ; Coninx, Ingrid ; Och, Renze van - \ 2016
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2768) - 25
bedrijven - energiebesparing - natuur - nederland - businesses - energy saving - nature - netherlands
Energiebesparing met LED belichting in gerbera : resultaten van 1ste jaar LED onderzoek
García, Nieves ; Weerheim, Kees ; Helm, Frank van der; Kempkes, Frank ; Visser, Pieter de; Groot, Marco - \ 2016
Bleiswijk : Wageningen UR Glastuinbouw (Report GTB 1389) - 66
gerbera - glastuinbouw - kasgewassen - kassen - kastechniek - teelt onder bescherming - energiebesparing - led lampen - kunstlicht - kunstmatige verlichting - licht - verlichting - greenhouse horticulture - greenhouse crops - greenhouses - greenhouse technology - protected cultivation - energy saving - led lamps - artificial light - artificial lighting - light - lighting
In the winter 2013-2014 Wageningen UR Greenhouse Horticulture conducted studies on energy saving opportunities in the cultivation of gerbera, CV Kimsey. The research was funded by the program Greenhouse as Energy Source from the Ministry of Economic Affairs and LTO Glaskracht. The contribution of LED lighting, LED interlighting, a lower intensity of the light installation, and light integration was investigated. An electricity savings of 45% was the target. By using LED lighting a 20% electricity savings are possible in exchange for a small production loss (2.3%) and some additional heat demand (9%). By installing 80 instead of 100 μmol light gerbera growers can save another 20% energy costing only 3.9% production without sacrificing quality. The targeted PAR sum for light integration was too high to contribute to electricity savings. The use of 20 μmol LED interlighting in combination with 60 μmol top light (LED or SON-T) resulted in significantly less production (9%) and lower flower quality: shorter and lighter, smaller diameter and a lower % of dry matter) than 80 μmol top light.
Filmpje: Paprika, schermen bij tropisch weer, geen binnenrot
Gelder, A. de - \ 2016
Kasalsenergiebron.nl
paprika's - gewasproductie - energiebesparing - energiegebruik - gewaskwaliteit - glastuinbouw - teeltsystemen - sweet peppers - crop production - energy saving - energy consumption - crop quality - greenhouse horticulture - cropping systems
Het weglaten van de minimumbuis en het gebruik van twee energieschermen elke nacht, ook tijdens de warmste dagen in augustus, waren de opvallendste aspecten tijdens het onderzoek ‘Paprika energiezuinig met een goede kwaliteit’. Aat Dijkshoorn (LTO Glaskracht Nederland), Jeroen Zwinkels (Delphy), Arie de Gelder (Wageningen University & Research) en telers Danny van der Spek (Paprikakwekerij Van der Spek) en Maikel van den Berg (Quality Peppers) vertellen in dit filmpje over deze opvallende resultaten van het onderzoek.
Consultancy genereren basiskennis fotosynthese aardbei
Kaiser, E. ; Janse, J. - \ 2016
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1411) - 22
aardbeien - fragaria ananassa - teelt onder bescherming - kasgewassen - glastuinbouw - fotosynthese - energiebesparing - licht - kooldioxide - strawberries - protected cultivation - greenhouse crops - greenhouse horticulture - photosynthesis - energy saving - light - carbon dioxide
To save electricity and CO2 during strawberry production, more knowledge about the photosynthesis of greenhouse-grown strawberry plants is necessary. This was tackled by measuring light- and CO2-dependent photosynthesis responses and by conducting a literature study in which several parameters of leaf-level photosynthesis were compared. From measurements conducted between middle of March and middle of May 2016 it was concluded that the rate of photosynthesis and electron transport was comparable between young and old leaves, while stomatal conductance in young leaves was always higher. Light- and CO2- saturated photosynthesis rates were higher in older leaves. Furthermore, a decrease of photosynthesis rates was visible in April, which may have been caused by acclimation of leaf biochemistry to elevated CO2 concentrations in the greenhouse. Conclusions from the literature study were that light saturation was reached at ~1000 μmol m-2 s-1 and that CO2 saturation was reached at ~1100 μmol mol-1. Average photosynthesis rates at these conditions were 18 and 35 μmol m-2 s-1, respectively. The average quantum yield of photosynthesis was ~0.06 μmol CO2 μmol-1 PAR, which is comparable to other, fast growing greenhouse crops (e.g. cucumber, tomato, sweet pepper). Large knowledge gaps about the course of photosynthesis during complete growing seasons remain.
Duurzaamheid als leidraad voor roos : vervolg onderzoek Perfecte Roos: energiezuinig geteeld
Gelder, Arie de; Warmenhoven, Mary ; Knaap, Edwin van der; Burg, Rick van der - \ 2016
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1412) - 50
rozen - teelt onder bescherming - kasgewassen - glastuinbouw - duurzame landbouw - energiebesparing - elektriciteit - assimilatie - kunstlicht - kunstmatige verlichting - verlichting - koelen - meeldauw - geïntegreerde bestrijding - geïntegreerde plagenbestrijding - roses - protected cultivation - greenhouse crops - greenhouse horticulture - sustainable agriculture - energy saving - electricity - assimilation - artificial light - artificial lighting - lighting - cooling - mildews - integrated control - integrated pest management
The project Sustainable rose cultivation aimed to achieve a sustainable and energy efficient rose cultivation by a controlled use of assimilation lighting, an optimum use of the cooling and an integrated control strategy for mildew. The production came to 320 stems.m-2 average weight 54 grams. The branch length and bud size varied through the season. There was no saving on electricity. There was a significant saving on heat. The improvement of the energy efficiency was totally determined by the reduction of the heat consumption. The light utilization efficiency was 2:44 g.mol-¹ and increased compared to the previous year. Cooling and forced ventilation had a positive effect on the stem elongation in the autumn. The installation with forced ventilation from above combined with the screen had a favourable effect on the climate, especially in the humidity control under a largely (95-98%) closed screen. The payback period of the investment in airconditioning is within 3 years.
Plantmonitoring op basis van fotosynthese sensoren : ontwikkelen en testen van sensoren
Dieleman, Anja ; Bontsema, Jan ; Jalink, Henk ; Snel, Jan ; Kempkes, Frank ; Voogt, Jan ; Pot, Sander ; Elings, Anne ; Jalink, Vincent ; Meinen, Esther - \ 2016
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1405) - 86
teelt onder bescherming - glastuinbouw - kastechniek - sensors - fotosynthese - kooldioxide - energie - energiebesparing - verlichting - kunstlicht - kunstmatige verlichting - ventilatie - kunstmatige ventilatie - fluorescentie - tomaten - solanum lycopersicum - protected cultivation - greenhouse horticulture - greenhouse technology - photosynthesis - carbon dioxide - energy - energy saving - lighting - artificial light - artificial lighting - ventilation - artificial ventilation - fluorescence - tomatoes
The basic process for crop growth and production is photosynthesis. Measuring crop photosynthesis is therefore important to monitor the status of the crop and whether the greenhouse climate is set to the needs of the crop. In this project, two monitoring systems for crop photosynthesis were developed and tested. (1) The crop photosynthesis monitor is a soft sensor that can calculate the CO2 uptake of an entire crop. The basis for these calculations are the balance between CO2 supply and CO2 loss via ventilation and crop photosynthesis. By measuring the CO2 concentration and humidity inside and outside the greenhouse, the crop photosynthesis can be calculated. (2) The CropObserver is a fluorescence sensor that measures the light use efficiency of photosynthesis of a large crop area (3 x 3 m2). The crop receives light pulses from a laser in the top of the greenhouse, the sensor measures the fluorescence signal of the crop. Both sensors were tested in a tomato crop in 2014 with promising results. The sensors functioned without problems and delivered patterns of daily photosynthesis which matched the reference measurements reasonably well up to well.
Philosophising about The New Crop : 'Open crop can bring forward production and save energy'
Gelder, Arie de - \ 2016
horticulture - greenhouse horticulture - vegetables - tomatoes - plant development - crop production - energy saving - yields - leaf area - agricultural research

Research into the extreme removal of leaves from tomato plants has yielded surprising results. Not only does it seem possible to bring forward production by removing extra leaves but it also saves energy. The challenge now will be to see if the results achieved in research units at Wageningen UR Greenhouse Horticulture can be reproduced in practice

2SaveEnergy-Gewächshaus- Produktion und Energieverbrauch
Kempkes, F.L.K. ; Janse, J. - \ 2016
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1404) - 46 p.
greenhouse horticulture - greenhouse crops - greenhouse technology - energy saving - energy consumption - isolation - isolation techniques - tomatoes - solanum lycopersicum - glastuinbouw - kasgewassen - kastechniek - energiebesparing - energiegebruik - isolatie - isolatietechnieken - tomaten
Energy savings through a greenhouse cover of insulation glass requires a large investment. In the search for a cheaper alternative by a consortium of companies consisting of VDH Plastic Greenhouses, Van der Valk Horti Systems, AGC Chemicals Europe en Boal Systems a Glass-Film-greenhouse cover, better known as the 2SaveEnergy greenhouse concept was realized in summer 2014. The combination of clear glass with a diffuse ETFE film and a double screen mounted at a distance of only a few centimetres, in the year 2015, resulted in a low energy consumption and a better than expected good tomato production. During cultivation, the principles of the new cultivation methods were used. With respect to the common practice, the energy consumption was more than 50% lower at a minimum equal production.
Teelt en energie 2SaveEnergy kas
Kempkes, F.L.K. ; Janse, J. - \ 2016
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1402) - 42 p.
glastuinbouw - kasgewassen - kastechniek - energiebesparing - energiegebruik - isolatie - isolatietechnieken - tomaten - solanum lycopersicum - greenhouse horticulture - greenhouse crops - greenhouse technology - energy saving - energy consumption - isolation - isolation techniques - tomatoes
Energy savings through a greenhouse cover of insulation glass requires a large investment. In the search for a cheaper alternative by a consortium of companies consisting of VDH Plastic Greenhouses, Van der Valk Horti Systems, AGC Chemicals Europe en Boal Systems a Glass-Film-greenhouse cover, better known as the 2SaveEnergy greenhouse concept was realized in summer 2014. The combination of clear glass with a diffuse ETFE film and a double screen mounted at a distance of only a few centimetres, in the year 2015, resulted in a low energy consumption and a better than expected good tomato production. During cultivation, the principles of the new cultivation methods were used. With respect to the common practice, the energy consumption was more than 50% lower at a minimum equal production.
‘Controlled removal of moisture results in energy savings’ : energy balance highlights the losses
Raaphorst, Marcel ; Zwart, Feije de - \ 2016
horticulture - greenhouse horticulture - dehumidification - energy balance - energy saving

By using a model to show the energy balance in a greenhouse you can see at a glance where the energy losses are likely to arise. Evaporation uses expensive energy and this rushes out the vents when a grower opens them to reduce the relative humidity. This can be done differently say Dutch researchers of Wageningen UR Greenhouse Horticulture. The more uniform the greenhouse climate the more the relative humidity can be allowed to rise.

Verhoging van energie-efficiency bij intensieve glastuinbouw productiesystemen : ontwikkeling van high-tech sensorsystemen voor monitoring en besturing van energiezuinige kassen: Fibre Bragg glasvezelsensoren
Balendonck, J. ; Janssen, H.J.J. ; Zwart, H.F. de; Schriek, L. ; Toet, P. ; Bezemer, R.A. ; Ruijs, M.N.A. - \ 2016
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1392) - 78 p.
teelt onder bescherming - kasgewassen - kassen - intensieve productie - energiebesparing - sensors - temperatuur - relatieve vochtigheid - protected cultivation - greenhouse crops - greenhouses - intensive production - energy saving - temperature - relative humidity
Wageningen UR Greenhouse Horticulture and TNO conducted a study on the application of Fibre Bragg optic sensors to measure temperature and relative humidity in greenhouses at high spatial density. Sensors, incorporated in an experimental enclosure, were evaluated under practical conditions in a greenhouse at Bleiswijk (NL). Their performance appeared to be similar to that of existing wireless electronic sensors. In order to save energy when using their heating, growers may so obtain relative humidity at higher spatial density and grow at a higher average humidity level. Sensors indicate at an early stage if there is condensation and consequently a higher risk on diseases somewhere in the greenhouse. Rule of thumb is that every percent increase in the humidity will yield about 3.5% of energy or 1 m³ natural gas equivalents. In addition to energy saving, investing in a distributed monitoring network also has an economic advantage. Another advantage is that fiber-optic sensor networks can be extended to larger areas and with other sensor types at little more costs. However, little research and no practical experience is gained with fiber optic sensors in greenhouses. More research is still needed in order to arrive at a system ready for practice.
Energie-extensieve teelten klimaatneutraal met hoog-isolerende kassen
Zwart, H.F. de; Garcia Victoria, N. ; Kromwijk, J.A.M. ; Kempkes, F.L.K. - \ 2016
Bleiswijk : Wageningen UR Gastuinbouw (Rapport GTB 1398) - 40 p.
glastuinbouw - extensieve productie - antirrhinum - aardbeien - slasoorten - duurzaamheid (sustainability) - energiebesparing - ontvochtiging - isolatietechnieken - verwarming - belichting - licht - lichtdoorlating - biologische grondontsmetting - greenhouse horticulture - extensive production - strawberries - lettuces - sustainability - energy saving - dehumidification - isolation techniques - heating - illumination - light - light transmission - biological soil sterilization
In this study an analysis is presented on the perspectives of highly insulated greenhouses for extensively heated
greenhouse crops. Three crops were used as an example, ranging from Antirrhinum, with a yearly heating
demand of 4 m³ of natural gas equivalents per m² to strawberry, with 13 m³ of gas consumption per m² per
year.
If Antirrhinum would be grown in a double glazed, highly insulated greenhouse with an energy recuperating
dehumidification system, the remaining heat demand will be almost zero. Growing strawberries in such a
greenhouse reduces the gas consumption for heating down to 7 m³/(m² year). When generating this heat
with a heat pump, only 21 kWh/(m² year) will be needed for heating. In all greenhouse sectors, a tendency
towards an intensified production by using artificial illumination can be seen. Illumination has a much higher
impact on energy consumption than heating, so insulation of greenhouses for extensively heated crops is of less
importance than improving the transmissivity or developing better lighting systems.
Besides energy for heating and lighting, greenhouses use a substantial amount of energy for soil disinfection.
Here savings can be achieved by using biological disinfection, substrate systems or ozonized water.
This project was funded by the research program ‘Kas als Energiebron’, the joined action and innovation program
of the ministry of Economic affairs and LTO Glaskracht Nederland.
Lisianthustelers kunnen alleen grenzen opzoeken in een proef : door met onderzoek energiebesparing en teeltsystemen
Raaphorst, Marcel - \ 2016
horticulture - greenhouse horticulture - cropping systems - energy saving - eustoma grandiflorum - cut flowers - agricultural research - testing

Een van de meest gecompliceerde proeven bij het GreenQ Improvement Centre is de volveldse lisianthusteelt met recirculatie. De doelstelling is 35% op energie besparen bij een gelijke productie en kwaliteit. De lat ligt erg hoog, misschien zelfs iets te hoog. Na acht teeltrondes zijn de telers wel een stuk verder gekomen.

New wastewater treatment concepts towards energy saving and resource recovery
Khiewwijit, R. - \ 2016
University. Promotor(en): Huub Rijnaarts, co-promotor(en): Karel Keesman; Hardy Temmink. - Wageningen : Wageningen University - ISBN 9789462576407 - 148 p.
waste water treatment - energy saving - recovery - municipal wastewater - nutrients - volatile fatty acids - afvalwaterbehandeling - energiebesparing - terugwinning - stedelijk afvalwater - voedingsstoffen - vluchtige vetzuren
At present, conventional activated sludge (CAS) systems are widely applied to treat municipal wastewater. The main advantages of CAS systems are that they are robust and generally produce an effluent quality that meets the discharge guidelines. However, CAS systems cannot be considered sustainable because they consume large amounts of energy (mainly for aeration and sludge treatment), have a high CO2 emission and do no recover a potential resource of water, energy and nutrients nitrogen (N) and phosphorus (P). Therefore, in this thesis new municipal wastewater treatment concepts that combine treatment with recovery of valuable resources and can save considerable amounts of energy were investigated by modelling and experiments.

Quantitative numerical results showed that the feasibility of two novel wastewater treatment configurations, including combined bioflocculation and anaerobic digestion but with different nutrient removal technologies, i.e. (cold) partial nitritation/Anammox or microalgae treatment, is location dependent. Using Dutch municipal wastewater and climate conditions, the configuration with cold partial nitritation/Anammox is the most promising wastewater treatment concept, because it can: 1) treat wastewater year round; 2) produce an effluent at a quality that meets the discharge guidelines; 3) reduce CO2 emission by 35% compared to the CAS system; 4) achieve a net energy yield up to 0.24 kWh per m3 of wastewater compared to a negative net energy yield of -0.08 kWh per m3 of wastewater for the CAS system; and 5) recover 80% of the sewage P. Additionally, the feasibility of the two configurations was investigated for 16 locations around the globe. The results quantitatively support the pre-assumption that the configuration with (cold) partial nitritation/Anammox is applicable in tropical regions and some locations in temperate regions. The configuration with microalgae treatment is only applicable the whole year round in tropical regions that are close to the equator line. The results also showed that the configuration employing microalgae treatment has an advantage over the configuration employing partial nitritation/Anammox with respect to consumption of aeration energy and recovery of nutrients, but not with respect to area requirements. For a tropical climate country like Thailand, the net energy yield of both configurations is at least a factor 10 higher than the CAS system, while CO2 emission is at least 22% lower.

In CAS systems energy recovery from wastewater is accomplished by anaerobic digestion of the organic solids in primary and secondary sludge into methane. However, volatile fatty acids (VFA), which are intermediate digestion products, may be preferred over methane, because VFA can be used as starting compounds for a wide range of higher value products. In this thesis the experimental results showed that a combined process with bioflocculation, using a high-loaded membrane bioreactor (HL-MBR) to concentrate sewage organic matter, and anaerobic fermentation, using a sequencing batch reactor to produce VFA is technologically feasible. An HL-MBR operated at a hydraulic retention time (HRT) of 1 hour and a sludge retention time (SRT) of 1 day resulted in very good performance, because as high as 75.5% of the sewage COD (chemical oxygen demand) was diverted to the concentrate and only 7.5% was mineralized into CO2. It was also found that 90% of the sewage NH4-N and PO4-P were conserved in the HL-MBR permeate, which can be reused as irrigation water as it is free from solids and pathogens.

During anaerobic fermentation of the HL-MBR concentrate at an SRT of 5 days, 35°C and without pH control, methane production was inhibited, but incomplete solids degradation mainly limited the VFA production as only 15% of the sewage COD was converted to VFA. Thus, the VFA yield needed to be increased. It was hypothesized that high pH (pH 8–10) fermentation combined with a long SRT, allowing for sufficient solubilization of solids and colloidal COD, can improve the VFA yield. In the current study, it was found that application of a pH shock of 9 in the first 3.5 hours of a sequencing batch cycle followed by a pH uncontrolled phase for 7 days gave the highest VFA yield of 440 mg VFA-COD/g VSS and this was equivalent to 26% of the sewage COD. This yield was much higher than at fermentation without pH control or at a constant pH between 8 and 10. The high yield in the pH 9 shock fermentation could be explained by: 1) a reduction of methanogenic activity; or 2) a high degree of solids degradation; or 3) an enhanced protein hydrolysis and fermentation. This study also demonstrated that the VFA yield can still be further optimized by fine-tuning pH levels and longer operation, possibly with fermentative microorganisms adapted to a high pH that are commonly found in nature. This would further increase VFA yield to 33% of the sewage COD.
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