The invention relates to a method of intensive plant cultivation in a production unit connected to a waste water treatment system.

Background of the invention

In recent years, the application of so-called membrane treatment processes known as MBR (membrane biological reactors) has been more and more promoted in the field of wastewater treatment technologies and waste water treatment processes. The essence of their application lies in the possibility to strictly separate the cleaning culture from the purified water with specially manufactured plastic membranes with a mesh size from 0.01 to 0.07 microns. Good separability of purified water from the cleaning culture (activated sludge) makes it possible to increase the concentration of active biomass, and, in addition, there is no need to build secondary sedimentation facilities. A big advantage of membrane processes is the possibility to increase the concentration of biomass which is 2 to 4 times higher in comparison to conventional systems. This leads to a situation in which the organic load brought to a volume unit is proportionally higher, and thus the whole wastewater treatment plant has lower volumes and thus lower investment costs. Wastewater treatment is also a source of greenhouse gases and odours, and it also produces large quantities of waste sludge. Their liquidation continues to require additional resources, which makes the operation more expensive, and generated greenhouse gases are the subject of deteriorating climatic conditions in the world.

Summary of the invention

The solution presented by the invention lies in the combination of highly effective

biotechnological methods for wastewater treatment which takes place in an integral biotechnology reactor complemented with an intensive production unit for growing plants, flowers, crops, etc.

The subject of the invention is that the production unit is connected to an integral

biotechnology reactor for wastewater treatment to accelerate the photosynthesis of plants, synergically using carbon dioxide (CO2) generated during biotechnological degradation of pollutants, and simultaneously using oxygen (O2) released by the photosynthesis of plants. It forces it as compressed air with a higher content of oxygen (O2), from the inner space of the greenhouse where the production unit is situated, back to the operational space of the reactor, thereby increasing the biological activity of micro-organisms involved in the biological wastewater treatment. At the same time, it uses the wastewater waste heat which is taken from the purified water using heat pumps, and then it is used for heating the greenhouse space above the biotechnology reactor. Heat pumps for the accumulation of electricity produced by photovoltaic panels are powered by a battery. The greenhouse space and the production unit are advantageously illuminated with LED light sources in the day or night operation according to the requirements for the production of plants. Sludge from purified wastewater may be used as a source of ions and fertilizers for growing plants.

The production unit includes a vertical system of hydroponic or aeroponic growing of crops in mobile or stationary shelves.

This invention advantageously uses carbon dioxide (C0 ₂ ) generated in the purification process to accelerate the photosynthesis of plants. It simultaneously uses heat from wastewater which is drawn from the purified water using heat pumps, and then uses it for heating the greenhouse space above the wastewater treatment plant. This combined production unit enables, using photovoltaic cells and appropriately selected batteries, a sufficient lighting level with LED lamps also in a night operation and, in particular, it uses the moisture from the space above the wastewater treatment plant and treated sewage sludge (as fertilisers) and water for irrigation, thus achieving significantly better cultivation results with better economic efficiency. The invention enables the synergic use of CO2 generated in biotechnological decomposition of contaminants to enhance the photosynthesis and also the use of oxygen released by the photosynthesis of plants to the greenhouse space from, where with blowers, it is blown back into the aeration distribution system of the wastewater treatment plant as compressed air with a higher oxygen content. It was demonstrated that increase of oxygen partial pressure in activation systems increases the biological activity of micro-organisms involved in biological water purification. It has a positive impact on the economy of wastewater treatment plant operation, but especially minimises the release of greenhouse gases into the atmosphere and the system as a whole with dependence reduction of plant and crop production in climatic conditions and seasonal variations. Heating of the greenhouse space with the use of low-potential heat from the purified water and a heat pump exchanger reduces the cost of crop production and increases the solubility of O ₂ in purified water (lower the temperature means higher solubility of O2 in water).

It is basically a two-component technology system. In the lower part, the wastewater is treated and sludge generated and in the upper single or multi-storey part, crops are grown. The main objective is to take advantage of the synergism of decomposition of organic matter contained in water when CO2 is generated and this CO2 is returned by plants and

photosynthetic processes as O2 to strengthen the process of water purification. It also uses waste low potential heat of water, sunlight and photovoltaic cells and batteries, as well as treated water for irrigation and sewage sludge as fertilisers and a source of ions. This reduces waste, the cost of water treatment and the production of fresh food, and, in particular, it reduces the so-called carbon footprint for transport. The food reaches the customer always fresh and always with high nutritional and vitamin value without freezing and dependence on distant traffic, which is a big problem especially in the Scandinavian countries and in winter conditions. There the production is literally "across the street" and harvested a few hours before consumption, without dependence on climatic conditions of the region.

Emphasis is placed, in particular, on compliance with all health conditions, so that the air in the system is filtered, all rooms are air conditioned and waste is strictly separated from the production area where maximum sanitary conditions are ensured. All the important processes are computer-controlled and automated.

Brief description of the drawings

The attached figures show examples of embodiments of the presented invention.

Fig. 1 and 2 show an overall view of the combined wastewater treatment system

complemented with a production unit for growing plants. Fig. 3 shows the interior of the system with exchange of C0 ₂ and 0 ₂ between the production unit and the wastewater treatment plant.

Fig. 4 - 6 show the production unit with a vertical system of crops growing. Fig. 7 and 8 show a view of the wastewater treatment plant combined system with a production unit, with a photovoltaic power system. Fig. 9 illustrates the basic conventional systems of hydroponic crop growing. Fig. 10 shows examples of mobile vertical plant growing systems, fig. 11 shows stationary plant growing systems. Fig. 12 shows a schematic arrangement of the production unit for growing crops with examples of the crops.

Examples of preferred embodiments

Arrangement of the wastewater treatment system and its use in agriculture production involve a combination of highly effective biotechnological methods for wastewater treatment, which take place in the integral biotechnology reactor. The system is supplemented with and intensive production unit for growing plants, flowers, crops etc.

This unit advantageously uses CO2 generated in purification processes to accelerate the photosynthesis of plants, uses heat from waste water which is taken from the purified water using heat pumps, and then it is used for heating the greenhouse space above the wastewater treatment plant. This combined unit enables, using photovoltaic cells and appropriately selected batteries, a sufficient lighting level with LED lamps also in a night operation and, in particular, it uses the moisture from the space above the wastewater treatment plant and treated sewage sludge as fertilisers and water for irrigation, thus achieving significantly better cultivation results with better economic efficiency.

The wastewater treatment method with an advantageous structure of vertical farming whose goal is to implement a strategy of a profitable, self-sustaining system in the management of wastewater treatment. The system provides local, fresh crops for urban population as an alternative to the current model of the globalised model based on food delivery. The main output of the system consists of crops sold on the local market.

Population studies show that the number of people continues to grow, and by 2050 it will reach 9 billion. Due to urbanisation, the majority (over 60%) of people will live in large cities where there is not enough food. As in other sectors, there as well will there not be enough space for their production. This situation is leading to a search for new ways of producing large quantities of food with higher efficiency and good quality in a smaller area. The vertical farming method is known to produce more food in any climatic conditions with high quality and in sufficient quantity. This method is based on growing food in halls and towers, and it can grow up to 100 times more food than conventional farming in the same area. The system uses vertical rack stacking and it can be built at any location, regardless of the climatic conditions.

Combination of wastewater treatment plants and vertical farming is a new way of connection of wastewater treatment with the production of large quantities of nutritious and high-quality fresh food throughout the whole year, without having to rely on experienced professionals, favourable weather and high soil fertility, and without large water consumption. By-products of wastewater treatment are the necessary inputs for the creation of a known climatic environment like in a greenhouse (aeroponics, hydroponics), providing basic needs such as light, heat, nutrients, air and carbon dioxide. Thanks to the new LED lighting technology, the demand for electric power necessary to ensure sufficient illumination of crops also decreases. In addition, the systematic growing, aimed at reducing the energy and material consumption, uses the results of current research, e.g. effective pyrolysis, window blinds sequence (lampshades), performance system, etc.

Smart technologies built into the system of the presented invention offer many advantages, such as:

• A stable and reliable growing season allowing commercial growers to safely commit to compliance with plans of supplies and contractual conditions. There are no "seasonal crops" or loss of crops. • A fully closed environment with regulation of climatic conditions eliminates environmental influences, such as diseases or pest attacks.

• Minimal energy consumption with maximum crop growth. Computer controlled

wavelengths for photosynthesis in accordance with the growth phase also contribute to the minimum energy consumption and optimal yields.

• The opportunity to use green energy and to get rid of tractors, irrigation pumps and other gardening equipment powered by fossil fuels.

• Reduction of water consumption in comparison with the traditional farming in the fields.

• A completely closed system eliminates the dependence on geographical location.

• A larger growing area than in single level hydroponic or greenhouse systems. More compact design makes it possible to establish affordable farms in industrial areas, urban warehouses and other low-cost and mostly unused locations which would not have been connected to high-quality and highly profitable agricultural activities before.

• Achieving more harvests per year than in traditional agriculture or other farming

methods. There is a wider variety of crops in a computer controlled environment with an extensive database which regulates and controls optimal growth conditions for each specific species of crop.

• Profitability in commercial horticulture requires the ability to consistently deliver

affordable crops under optimal conditions, from germination to harvest.

• Requirements for optimal growth thanks to a fully integrated computer control system.

Temperature and humidity values are monitored and maintained in the optimal range for each grown crop. CO2 may be delivered to storage installations, which further accelerates crop growth and increases yields.

• The maximum growth rate is achieved through lighting system with low energy LEDs which emit light in a special part of the spectrum which is used by crops at different stages of growth. This is programmed in a computer control system. All this has a significant effect on the growth rate and yield of plants.

Crop growing and crop production platform

• The crop selection and crop growth platform proposal determine the inputs and outputs of vertical farms. The proposal of cultivation area is done to obtain an estimate of the total production of fresh biomass and the total amount of inedible waste biomass.

• Most vegetables and fruits now available on the market can be grown in vertical farms.

Vertical farming economy also promotes the growing of crops with a short growing season, i.e. lettuce, strawberries, herbs and spinach. It is also necessary to consider the area needed for volume production of various crops. • Depending on the selected crops, it is necessary to design the width and height of growing to ensure appropriate conditions for efficient growing. Each crop has different requirements for line distance, production and profit per square metre and therefore, they cannot be similar.

• For example, lettuce roots distance ranges from 20 to 30 cm. Similarly, for tomatoes there should be 1 - 4 plants per square metre. For these reasons, the accurate determination of plant species determines the maximum area for root systems, production volume and economic gains.

• Vertical farming may be designed as hydroponic or aeroponic, with a supply of water, nutrients to crops and roots. In a hydroponic system (DWC, NFT or BBC), the root system grows in solutions of nutrients and minerals or in an inert medium. The root system of aeroponics is sprayed with mist of mineral solutions delivered with a pipeline.

• The materials used in the vertical farming for germination and growth include

compressed peat, coconut fibres or glass wool in hydroponic systems. While during the growth phase, the plants may be placed on the pallet without the use of inert materials (aeroponic system), at the stage of germination it is appropriate to use these materials for easier handling and reinforcement of roots. Likewise, plants with larger produce must have a proper root system which ensures stability of the plant.

Crop growth platforms are selected according to the needs of crops and the chosen system. The table below shows some examples of line distances and yields per square metre in traditional growing.

Recent studies suggest up to 100-fold yields in comparison with traditional farming. Growing pallets can be designed as stationary or mobile for easy harvesting. The produce from higher levels is harvested using a ladder. In the case of mobile pallets, the produce can be easily harvested from the ground.

The system of growing crops on shelves

The system of growing crops on shelves is one of the most used hydroponic or aeroponic systems of vertical cultivation. The number of troughs is calculated according to the plant height, including the root system.

One growing trough consists of three main areas: growing pallet (space for the root system), space for plants and space for LED lighting. The space for the root system ranges from 0.15 m for strawberries to 0.4 m for potatoes. Generally, less space for the roots means a larger and more productive over-ground part of the crops. Plants with underground produce require higher pallets for proper development of produce. Space for the plant depends on the selected crop and determines the number of troughs per length unit in the vertical direction. In addition, the building height defines the number of troughs for a single cultivation system. While the volume of production increases with the number of troughs per square metre of built-up area, harvesting of crops becomes more difficult. If the system of shelves is higher than 2 metres, harvesting must be done from a service platform.

The table above contains basic parametres for crop growing design. Thanks to the lighting design used for vertical farming, the distance of lighting from plants can be less than 0.5 metre. A-shaped tower

A-shaped towers are suitable for crops with the height of the growth up to 0.5 m, i.e.

strawberries, radish, lettuce or baby spinach. Towers for vertical growing are supplied in a configuration with a height of 3 m, 6 m and 9 m and 6 m ² ground plan.

Each tower is formed from 12 to 36 storeys of growing troughs which rotate around an aluminium frame of the tower at a speed of 1 mm per second to ensure uniform sunlight illumination, sufficient air flow and irrigation of all plants.

This hydroponic system is irrigated with micro-spraying, or water can be supplied directly to the growing troughs. The rotary device does not require an electric motor; it is driven by a unique water system on the basis of gravity which consumes one litre of water supplied from an above-ground rainwater tank.

Omega Garden system

The Omega Garden system may also be suitable for growing crops which do not have large produce. Many species of herbs may be grown in this system with excellent results. Most species of herbs for leaf or bud collection easily adapt to the conditions of nutrition, lighting and growing of the Omega Garden system. Especially, these species have achieved huge yields per growing season: basil, mint, feverfew, marjoram, thyme, oregano.

Lettuce is another foodstuff which has demonstrated excellent results in cultivation using the Omega Garden system. Leafy lettuce varieties achieve the best results and exhibit large volumes. Head lettuce also achieves good results but the heads may be more leafy than in the traditional cultivation due to the rotation of the gardens.

The Omega Garden system may contain 80 plants per rotary cylinder with additional central lighting. One omega cylinder occupies only 0.6 square metre of floor space. This hydroponic system uses for the growing cups irrigated with mineral solution. Crops Plants per system Floor area [m]

Mint

Feverfew

Marjoram

80 0,6

Thyme

Oregano

Lettuce

Lighting

One of the most important needs of plants is lighting. Plants, which suffer from lack of light, are long and thin as a result of efforts to reach the light. Lighting for the vertical farm is provided by sun or other sources, depending on climatic conditions, building height and the required production volumes. If the sunlight is sufficient for the needs of plants, artificial lighting is used only as a supplementary source of light. In winter or on cloudy days, fluorescent lamps or LED lighting is used. LED lighting is more efficient than fluorescent lighting in creation of suitable conditions for growing crops. These modules can be set for specific wavelengths according to the selected crop.

The task of the lighting is to ensure a sufficient amount of light and heat for all plants. The main goal is to achieve a uniform illumination on the horizontal plane but vertical arrangement of illumination supports effective growth of taller plants, i.e. tomatoes.

Lighting from above

Interior lighting (one or two rows) Thanks to the optimized construction, only a very small amount of heat is emitted to the plants. Distance of LED from the plants may be smaller for more efficient use of space. The new generation of LED lamps also emit less heat so the input load per given photon flux is lower and it provides almost no loss of light. New generation light emitting diodes LED reach to about five times the service life than conventional light sources. Rated life of LED module is 50,000 hours at 70% efficiency of initial photon flux (of guaranteed 25,000 hours at photosynthetic photon flux at 90%).

Higher volume production is also dependent on the amount of time of the lighting system. A sufficient light for most plants is 12 to 16 hours at a photon flux 200-300 pmol/m ² . The number of LEDs depends on the desired production volumes, an area of growing troughs and selected crops.

Red or blue light provided by LED panels with the width of about 4 - 5 cm is used according to phytochromes and vegetative phase.

Cooling is very important to ensure longer life and to prevent damage of the LED panels. Generally, 50-80% of the energy is converted to heat, with a negligible heating of the air, so it is necessary to cool the whole system.

The following table shows the photon flow and the number of hours of lighting needed for different types of plants.

Daylight [h] PPF fcmol/m2.s]

Cabbage 12 196.8

Carrots 16 196.8

Lettuce 16 196.8

Peppers 12 277.8

Peas 12 312.5

Radishes 16 196.8

Spinach 16 196.8

Strawberries 12 254.6

Tomatoes 12 312.5

Potatoes 12 324.1 Temperature requirements

Temperature is one of the most important parametres for high production efficiency which must be based on the selected crops. Proper temperature is achieved by using waste heat from the output water and heat pump.

The combined system ensures a constant temperature in summer and winter when the outside temperature drops.

Consumption of nutrients, water and carbon dioxide

Supply of nutrients and water is dependent on the chosen hydroponic or aeroponic system. Growing crops in the form of vertical farming is the most accurate method of growing which yields high production efficiency. This growing method requires periodic water analysis based on changes in nutrient content.

Purified water is a by-product of wastewater treatment. It is introduced in atomised or droplet form, or directly to the roots in an inert substance.

17 essential nutrients play an important role in maintaining the health of plants during their growth. All plants must have an adequate intake of nutrients to achieve optimal yields. By the law of minimum, if the system does not provide one or more nutrients, yields will be lower, even if there is a necessary quantity of other nutrients. Yields may be reduced by the element with the lowest supply which becomes the key nutrient needed for growth of the crop.

Moreover, they have different varieties during their growth and have different requirements for the quantity of supplied nutrients. The basic elements are received and incorporated in different amounts according to the stage of growth or flowering.

Macro-elemental nutrients such as phosphorus, nitrogen and potassium are necessary for photosynthesis, cell division and fructification. The main elements are delivered in the form of liquid fertiliser diluted in the correct ration. Water and carbon dioxide consumption is covered by the wastewater treatment plant and recycling system products. The correct amount of water containing the nutrients is supplied with a pump to the mixing tank and then with pipes to the pallet hydroponic system.

The air management system provides ventilation and air circulation, during which the majority of evaporated water is removed. To increase crop production, carbon dioxide from the developing tank is brought with a pipe. Plants consume 0.1 to 0.3 g of CO2 per gram of fresh biomass.

Apart from the production of carbon dioxide, this air contains water vapour, methane, H2S, mercaptans, dimethyl sulphide and ammonia in the form of volatile organic compounds. To avoid contamination of crops, it is necessary to clean the air using biological filters which rid the air of pollutants and enrich it with carbon dioxide. Biological filters operate on the principle of a biofilm which covers the particles of the used material and the fillings. Volatile contaminants are decomposed in the presence of oxygen in the wet biofilm and are metabolised with an aerobic process of microorganisms.

The mixing tank is also equipped with pH metres, sensors of nutrient content and level sensor which are connected to a computer and ensure constant quality conditions of the system. For the supply of the correct amount of carbon dioxide, the concentration of CO ₂ is measured with TESTO sensors.

Heat and electricity

Heat pump and cooling system

Photovoltaic cells and a set of batteries provide energy for temperature regulation and the heating and cooling system. The heating system uses water / water heat pump, which transfers heat from the output water. This heat is also used for heating. The cooling system, if required in the summer, will use a closed water / water system. The basis is that the photovoltaic system and the energy accumulation in the new generation of efficient batteries provide electricity supply for the entire system. The used water / water CIAT heat pump is designed as a heat source. The circulation pump of the primary and secondary circuit is installed at the inlet of the heat pump unit. Heat transfer from LED panels to the ambient air is negligible. All the heat from LED lighting is transferred to the cooling system. The building cooling, if necessary in the summer time, is provided with a cooling water / water system. This unit is closed and transfers heat to the output water.

Photovoltaic power system

Solar panels are installed on the covered parts of the vertical farm and on the roof of the building and next to it to ensure energy consumption of technological equipment and LED lighting. The glass roof is partially covered with glass solar panels which capture sunlight in its structure.

The photovoltaic power system consists of solar panels, DC/AC and AC/DC inverters, a converter and the main wall battery. Solar panels are placed on the roof and transform solar radiation into electricity.

DC/AC and AC/DC inverters control the flow of electric current. New technology of transparent solar panels allows the installation above a staircase or on side walls of the building as Windows, and reduce the intensity of interior lighting.

Energetic processing of sludge and waste biomass

The sludge extracted from a wastewater treatment plant (WWTP) and the waste biomass are used as a main source for energy recycling using a pyrolysis unit and a cogeneration unit. Here, further processing occurs in which it is necessary to reduce the moisture content by about 60%.

The pyrolysis unit will be placed separately near the outlet of the sludge. Hot air for drying the sludge and biomass is obtained by means of a heat pump which takes heat away from the output of water flowing into a tank.

Vertical farm design

The farm in the presented design is located in a temperate climate and the temperature in summer ranges between +20 and +30 °C. Climatic zone determines crop production. Import of fruits and vegetables and cultivation in greenhouses are the only ways to provide fresh produce in winter months.

A wastewater treatment plant with a vertical farm is a unique wastewater treatment project associated with cultivation of different crops. The vertical farm is located on the first floor in a circular area of 855 square metres. Depending on the needs of the population, different crops may be selected and it is possible to divide the area accordingly into zones with different microclimate, special lighting conditions, water and nutrient consumption and requirements for the heating and cooling system.