WO2017101955A1

WO2017101955A1 - High value biomass production in biological wastewater treament processes

Info

Publication number: WO2017101955A1
Application number: PCT/DK2016/050443
Authority: WO
Inventors: Kim Helmo; Anne-Belinda BJERRE
Original assignee: Helmo Consult V/Kim Helmo; Teknologisk Institut
Priority date: 2015-12-18
Filing date: 2016-12-16
Publication date: 2017-06-22

Abstract

The present invention relates to a process and a device for biological treatment of wastewater. In an overall perspective, the present invention is based on a treatment methodology according to which carbon is captured in/by bacteria while nutrients flows with the liquid of the pre-treated wastewater and wherein the pre- treated wastewater is fed to a photosynthetic organism e.g. algae, cyano bacteria, plants or water plants in order to simultaneously remove nutrients and obtain a biomass with potential high value compounds.

Description

HIGH VALUE BIOMASS PRODUCTION IN BIOLOGICAL WASTEWATER TREAMENT PROCESSES FIELD OF THE INVENTION

The present invention relates to a process and a device for biological treatment of wastewater. In an overall perspective, the present invention is based on a treatment methodology according to which non-treated wastewater is subjected to bacterial pre-treatment wherein carbon in the wastewater is captured in/by bacteria and converted to C0₂ and bacterial biomass while nutrients, such as N, P and/or K, remains substantially unaffected and flows with the liquid of the pre- treated wastewater and wherein the pre-treated wastewater is fed to growing photosynthetic organisms i.e. algae (microalgae and macroalgae), cyanobacteria and/or any plants including waterplants in order to simultaneously remove nutrients and obtain a biomass with potential high value compounds.

The invention relates to a process preferably comprising subjecting wastewater to an bacterial treatment thereby obtaining a pre-treated wastewater comprising low amount of carbon and high amount of unaffected nutrients (liquid phase) and a carbon dioxide (gaseous phase). The pre-treated wastewater is subjected to a separation treatment to obtain two fractions, the first fraction comprises a smaller content of suspended matter compared to the second fraction being mostly free of suspended matter. Subsequently to the bacterial treatment and separation treatment, the liquid wastewater fraction is fed to photosynthetic growing organism belong to the species of algae (microalgae and macroalgae),

cyanobacteria, any plants or water plants and adding light and at least a fraction of the carbon dioxide (14) obtained by the bacterial treatment, thereby obtaining biomass and oxygen. According to the invention, at least a fraction of the oxygen obtained by the algae and/or water plants is supplied to the bacterial treatment.

BACKGROUND OF THE INVENTION

Wastewater from e.g. household, agriculture and industry comprises excessive amounts of organic matter and nutrients. Traditionally, wastewater is collected and led to a biological wastewater treatment-plant where the carbon-, nitrogen and phosphate rich wastewater is degraded by bacteria through oxidation, nitrification and de-nitrification processes in the presence (nitrification) or absence (denitrification) of oxygen (0₂) into e.g. carbon dioxide (CO2), nitrous gasses (e.g. N2, N₂0, NO) and a low-value sludge product and water, the latter comprising N, P and organic matter.

The steps in a traditional wastewater treatment-plants (WWTP) are a combination of mechanical, chemical and biological processes to meet the effluent standards for outlet of organic matter, total nitrogen and total phosphate.

Larger particles are removed from the wastewater by means of a grid, bow sieve or the like. Then sands and fats are caught in aerated sand traps.

Next step will normally be a settling tank, where the smaller particles are sedimented and an aqueous phase with lower solids content is generated.

Typically, a reduction in the organic matter content of about one third is obtained by this step. Added cationic metal salts (iron, aluminum, etc.) or cationic polymers to the wastewater in the settling tank can be up to two-thirds of the organic matter is removed from the precipitated substance (primary sludge). The mechanical, physical and chemical pre-treated wastewater are then fed to the biological wastewater treatment. Today, processes are designed so that it treat both the organic matter, nitrogen and phosphate. By designing and split the process tanks into zones with different process conditions, it is possible that the same biological sludge can capture and convert organic matter, nitrogen and phosphate.

The pre-treated wastewater with suspended organism matter is first passed to an anaerobic step where the bacteria (biosludge) absorb and break down the organic matter, among other things by the hydrolysis and partly oxidation of long-chain carbohydrates, fats and proteins. In these conditions bacterial species will take up large amounts of phosphate and store it inside the bacterium.

In the next process step, air (oxygen) is supplied to the bio-sludge, where by the aerobic processes proceed. This runs the oxidative carbon decomposition and the time- and volume-consuming turnover of ammonium to nitrate (nitrification). Then follows an anoxic process step in which the supply of air is stopped and wherein the denitrification converts nitrates to atmospheric nitrogen (N2, N2O and other nitrogen oxides). The biosludge in the outlet from denitrification step is partly recycled to the anaerobic step and the nitrification step depending on both the biological phosphate uptake and turnover rate of nitrogen.

During the process cycle a new biomass (i.e. biosludge) is produced, resulting in a continuous withdrawal of surplus sludge to keep the level of the active biosludge relatively constant in the processes.

A large proportion of the wastewater treatment-plants still use chemical precipitation to remove phosphorus in the wastewater or combination of biological phosphate uptake and chemical precipitation.

In treatment plants, which have a digester tank the excess sludge and the primary sludge is dewatered in a dewatering unit and the solids are pumped to digestion. In the digester, the sludge is converted into methane, CO2, and an anaerobic biomass. Excess production of the anaerobic sludge is taken out for final dewatering.

At wastewater treatment plants not having a digester the surplus sludge is finally dewatered and taken out of the process.

Production of algae in connection with wastewater treatment has been disclosed in e.g. WO 2010/114522 however, with limited success since the bacteria and algae were produced in the same tank. In terms of process it is not interesting to link a bacterial biomass along with a biomass of photosynthetic organisms in a single step due to two factors. Firstly, the presence of a bacterial biomass cause turbidity in the water phase which prevents delivery of sufficient light to the algal biomass. The second fact is that bacterial biomass will enhance the shadow effect in that it will attach and grow on biomass of photosynthetic organisms' surface. By applying the method disclosed in WO 2010/114522 it is not possible to obtain a high value biomass since the presence of significant amounts of bacteria contaminate the final biomass.

Based on the above, it would, from an environmental perspective, be

advantageous if the water let out into the environment from the wastewater plant (i.e. the outlet effluent) comprised less nutrients (e.g. N, P, K) and if the gas (e.g. C0₂, N₂0 and methane) emitted from the wastewater plants could be reduced. Moreover, it would be of great economical interest, if high value products could be generated from wastewater.

OBJECT AND SUMMARY OF THE INVENTION

An object of the present invention is to provide a new and an alternative wastewater treatment to the prior art and in addition to provide an improvement over the prior art.

In particular, it may be seen as an object of the present invention to provide a process and a device that solves the above mentioned problems of the prior art namely by (i) reducing the content of nutrients (e.g. N, P and K) inside the wastewater treatment-plant as well as in the water let-out from the wastewater treatment plant (i.e. the outlet effluent), (ii) reducing the CO2, N₂0 and methane emitted from such wastewater plants and (iii) providing a significant biomass production of potential high value.

Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by providing a

device for treatment of wastewater, the device comprising :

- a bacterial treatment tank (5) having an inlet (10) for receiving

wastewater, such as non-treated wastewater for pre-treating the wastewater by bacterial treatment;

a biomass tank (6) in fluid connection (9) with the bacterial treatment tank (5) for receiving at least a fraction of the pre-treated wastewater from the bacterial treatment tank (6) and comprising a light source (4) adapted to expose the content in the biomass tank (6) to light for producing a biomass of photosynthetic organisms and an outlet (11) for outletting the biomass of photosynthetic organisms;

a first fluid connection (8) and a second fluid connection (7) each connection extend between the bacterial treatment tank (5) and the biomass tank (6);

wherein

the first fluid connection (8) is adapted to transport CO2 produced in the bacterial treatment tank (5) from the bacterial treatment tank (5) to the biomass tank (6) so as to feed photosynthetic organisms contained in the biomass tank (6) with CO2 produced by the bacteria;

the second fluid connection (7) is adapted to transport oxygen or oxygen containing gas, produced in the biomass tank (6) from the biomass tank (6) to the bacterial treatment tank (5) so as to feed bacteria contained in the bacterial treatment tank (5) with oxygen produced by the

photosynthetic organisms.

In the present context a number of terms are used in manner being ordinary to a skilled person. Some these terms are elucidated below:

Non-treated wastewater is preferably used to reference wastewater that has not been exposed to a biological and/or chemical treatment to remove N, P, and/or K. Non-treated wastewater may have undergone a mechanical treatment, such as filtering wherein larger solids of non-biological origin are removed from the wastewater.

A second aspect of the present invention pertains to a wastewater treatment plant (WWTP) comprising a plurality of the devices disclosed above.

A third aspect of the invention pertains to a process for treating wastewater, such as non-treated wastewater, the process comprising the steps of

(a) subjecting wastewater to an bacterial treatment, such as aerobic bacterial treatment, and obtaining

- pre-treated wastewater (13)

carbon dioxide (14)

(b) subjecting the pre-treated wastewater to a separation treatment and obtaining at least two fractions, the first fraction comprises a smaller content of suspended matter compared to the second fraction; and

(c) subsequently to said bacterial treatment, such as aerobic bacterial treatment, and separation

feeding the first fraction obtained above to photosynthetic organisms (d) adding light and at least a fraction of the carbon dioxide (14) obtained by the bacterial treatment, such as aerobic bacterial treatment, to the

photosynthetic organisms and obtaining biomass of photosynthetic organisms (15)

oxygen (16)

wherein at least a fraction of the oxygen obtained by the photosynthetic organisms is supplied to the bacterial treatment, such as aerobic bacterial treatment.

In a fourth aspect the invention pertains to a biomass obtained by the process disclosed above. In a fifth aspect the present invention pertains to the use of the process above for production of a biomass of photosynthetic organisms, water plant biomass, cyanobacterial biomass or any other plant derived biomass, fertilizer (solid and liquid based with also Ν,Ρ,Κ), a carbon source (feed to a digester), carbohydrates, proteins, lipids, bioactive compounds and combinations thereof.

It has been found that by utilising embodiments of the present invention, a number of advantages may be obtained, some of which will be disclosed in the following : - Uptil 80% of nutrients salts, N, P and K, can be removed compared to

traditional wastewater treatment facilities by growing photosynthetic organisms in the bacterial treated process water/wastewater (i.e. the pre- treated wastewater);

The total C02 emission from the wastewater treatment plant may be reduced with at least 50%, since C02 is bound as carbonhydrate in the photosynthetic organisms as a result of the photosynthesis;

As low as 25 % of the incoming nitrogen (N) is emitted to the atmosphere

(compared upto 90 % emission today), since nitrogen is bound in the photosynthetic organisms as protein;

- The produced bacterial biomass can be used as a direct source for biogas production and/or used in bio refining for production of a fertilizer, fodder, nutrient components and/or other biological high value products.

Thus, while prior wastewater treatment process and devices are designed with an aim to remove nutrient salts such as N, P and/or K, the present invention resides in the concept of keeping such salts in the pre-treated wastewater and making these salts available for photosynthetic organisms.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

The present invention and in particular preferred embodiments thereof will now be described in further details with reference to the accompanying figures. The figures show ways of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figure 1 is a schematic illustration of a first embodiment according to the invention of device for treatment of wastewater,

Figure 2 is a schematic illustration of a second embodiment according to the invention of device for treatment of wastewater Figure 3 is a schematic illustration of a third embodiment according to the invention of device for treatment of wastewater; in fig. 3a, a plurality of biomass tanks are arranged in series and in fig. 3b a plurality of biomass tanks are arranged in parallel, Figure 4 is a schematic illustration of a further embodiment of an algae treatment tank comprising a number of biomass tanks,

DETAILED DESCRIPTION OF THE INVENTION

Reference is made to fig. 1 illustrating schematically a device for treatment of wastewater. As illustrated in fig. 1, the device comprising a bacterial treatment tank 5 having an inlet 10 for receiving wastewater, such as non-treated

wastewater and the treatment tank is configured for pre-treating the wastewater by bacterial treatment. During use, the bacterial tank comprising beside the non- treated wastewater to be treated one or more strains of bacteria. In a preferred embodiment the bacteria are aerobic bacteria or a mix comprising aerobic and anaerobic bacteria. Thus, the bacterial treatment may be anaerobic or aerobic. In a preferred embodiment the bacterial treatment is aerobic. Such bacteria can be introduced into the tank 5 through a separate inlet (not shown) and/or be added to the wastewater such as non-treated wastewater to be treated before this water enters into the tank 5. The device shown in fig. 1 also comprises a biomass tank 6. This biomass tank comprising a light source 4 being adapted to expose the content in the biomass tank 6 to light for producing a biomass of photosynthetic organisms and having an outlet 11 for outletting the biomass of photosynthetic organisms.

In a preferred embodiment the photosynthetic organisms are selected from the group consisting algae such as but not limited to microalgae and macroalgae, cyanobacteria and plants such as but not limited to waterplants. The

photosynthetic organisms simultaneously remove nutrients, take up CO2 and produce a biomass with potential high value compounds.

Thus, at least two different treatment process are carried out in the device of fig. 1, namely a bacterial treatment and a biomass treatment. The bacterial treatment is a process using oxygen (O2) while producing CO2 and the photosynthetic organisms using CO2 while producing oxygen (O2) . In order to exploit that the product produced by the one of processes is utilizable in the other process (and vice versa), the device further comprising a first fluid connection 8 and a second fluid connection 7 where each connection extend between the bacterial treatment tank 5 and the biomass tank 6 as schematically illustrated in fig. 1.

The first fluid connection 8 is adapted to transport CO2 produced in the bacterial treatment tank 5 from the bacterial treatment tank 5 to the biomass tank (6) and the second fluid connection 7 is adapted to transport oxygen, or oxygen

containing gas, produced in the biomass tank 6 from the biomass tank 6 to the bacterial treatment tank 5. The fluid connections 7 and 8 are typically in the form of one or more tubes. It is noted that the transport of fluid in the two fluid connections 7 and 8 may be produced or at least assisted by one or pumps and/or regulated by one or more valves; these are not illustrated in fig. 1.

It is noted, that a filter or separator may be needed in order to avoid matter contained in the bacterial treatment tank 5 or in the bacterial treatment tank 6 from flowing into the connections 7 and/or 8. Further, the bacterial treatment tank 5 is in fluid connection 9 with the biomass tank 6 for receiving at least a fraction of the pre-treated wastewater from the bacterial treatment tank 5. In the embodiment shown in fig. 1, the fluid

connection 9 is illustrated as a screen allowing pre-treated wastewater to flow through the screen and into the biomass tank. However, the fluid connection 9 may be in form of one or more tubes.

It is noted that the wastewater such as non-treated wastewater entering into the the bacterial treatment tank 5 comprise nutrient salts such as nitrogen (N), phosphorus (P) and/or potassium (K) and that these nutrients salts are left generally unaffected (no actions are enforced to remove the nutrient salts except from the natural absorbtion/digestion by the bacteria). Therefore, the majority of the nutrient salts originally present in the non-treated wastewater are still present in the pre-treated wastewater and carried to the biomas tank 6 in which at least a fraction of the carried-over nutrient salts are at least partly absorbed by the photosynthetic organisms contained in the biomass tank 6.

Thus, it may be preferred that the bacterial pre-treatment removes as little as possible such as being economical feasible of the nitrogen (N), phosphorus (P) and potassium (K) originally present in the wastewater or the non-treated wastewater. Thus, the invention is preferably designed with the aim of carrying over to the biomass tank 6 as high amounts as possible of the nitrogen (N), phosphorus (P) and potassium (K) originally present in the wastewater or the non-treated waste waster.

Reference is made to fig. 2. In the embodiment shown in fig. 2, the fluid connection 9 between the bacterial treatment tank 5 and the biomass tank 6 comprises a bacterial separation element 12 (it is noted that bacterial separation element 12 is termed "bacterial" since it aims at removing bacteria/suspended matter). This separation element being adapted to receive pre-treated wastewater from the bacterial treatment tank 5, separate the received pre-treated wastewater into at least two fractions, the first fraction comprising a smaller content of suspended matter compared to the second fraction, the first fraction preferably contains less than 1 vol %, such as less than 0.5 vol %, preferably less than 0.3 vol %, such as less than 0.1 vol % of suspended matter and adapted to feed the first fraction to the biomass tank 6. As illustrated in fig. 2, the separation element 12 produces a stream of pre-treated wastewater (out of outlet 17) which may be either discharged or as it is preferred recycled back to the bacterial treatment tank 5.

It is preferably aimed at that the content of suspended matter is as low as possible in the first fraction (the fraction going into the biomass tank 6) since it is this fraction which may be feed to the biomass tank and since the content of suspended matter may affect the amount and quality of the biomas which may be produced in the biomass tank 6. Since the pre-treated wastewater (13) comprises water soluble nutrient salts, such as N, P and/or K, and the separation element 12 is designed not to filter-off such water soluble matter, such water soluble nutrient salts will go into the biomass tank 6 and be readily available for the

photosynthetic organism. Further, bacteria are typically comprised in floes, flocculated matter or similar which is separated off by the separation element 17, whereby the fraction fed into the bimass tank 6 is freed at least to some extend from bacteria but contains the nutrients salts thereby constituting a advantageous feed for the photosynthetic organisms. The term "suspended matter" also include solid matter. Thus, the second fraction (out of outlet 17), which may also be termed active sludge comprises e.g.

microorganisms, inorganic particles, organic fibres, filamentous bacteria, bacteria, extracellular polymer substances (EPS, biopolymers, exopolymers) and ions. The person skilled in the art will recognize that the composition and origin of the wastewater will affect the content of both the first and second fraction.

Thus, in a preferred embodiment the bacterial content in the first fraction is substantially smaller than the bacterial content in the second fraction. The bacterial content may be measured applying any known method of the art however, one way of measuring the bacterial content is to measure the total cell count my applying the direct microscopic count.

In the present context the term bacteria and microorganisms are used herein interchangeably. As indicated in fig. 2, the bacterial separation element 12 comprises an outlet 17 for outletting the second fraction. The outlet 17 may be connected to the bacterial treatment tank for inletting the second fraction, or at least a part thereof, to the bacterial treatment tank 5. Such a recycling to the bacterial treatment tank 5 may be in the form of one or more tubes and the flow may be produced or at least assisted by one or more pumps and the flow may be controlled by the pump possibly in connection with one or more valves. From this "second fraction" is taken surplus sludge, which is dewatered to a dry solids content of 15 - 25%. In the WWTP digester, this dewatered sludge converted to methane gas. Is the WWTP without digester, the dewatered sludge is spread on agricultural land, sent to an incinerator. The bacterial separation element may be a membrane filter, a settler, a cyclone, a lamella separator, lamella clarifier, a flotator, a device adapted to provide a chemical separation by use of e.g. inorganic salt, metallic salt or a polymer or a combination thereof. As mentioned, it may be contemplated to remove as much suspended matter as possible by applying this bacterial separation element.

As further illustrated in fig. 2, the device may further comprise an biomass separation element 18 connected to the outlet 11 of the biomass tank 6 for receiving the biomass. Such biomass separation element 18 is configured for separating out the biomass of photosynthetic organisms from the biomass streaming out from the biomass tank 6. To accomplish such a separation, the biomass separation element 18 may be the form of a membrane filter, a settler, a cyclone, a lamella separator, lamella clarifier, a flotator, a device adapted to provide a chemical separation by use of e.g. inorganic salt, metallic salt or a polymer or a combination thereof.

Thus, the biomass separation element 18 separates the biomass into at least two fractions, the first fraction comprising comprising a smaller content of biomass compared to the second fraction. With reference to fig. 2, the second fraction is reference 22 and this fraction can be used as further disclosed herein - or be recycled to the bacterial treatment tank 5. The first fraction can be used as disclosed below.

Preferably, the content of biomass in the first fraction is less than 1 vol. %, such as less than 0.5 vol. %, such as less than 0.1 vol. %. It may be preferred that the biomass separation element 18 removes as much photosynthetic organisms as possible since the amount of biomass separated ultimately affect the biomass output and thus, the efficiency and value of the device and process of the present invention.

As illustrated in fig. 2, the first fraction is fed into an ammonium/nitrate removal element 19, where the removed ammonium/nitrate leaves the element 19 as fraction labelled 21. The ammonium/nitrate removal 19 element may be configured for carrying out by a microbial nitrification/denitrification. Such an ammonium/nitrate removal element and step is preferably invoked when the content of ammonium/nitrate in the first fraction exceed predefined value, e.g. predefined by legislation.

The stream having gone through the ammonium/nitrate removal element 19 streams out from an outlet 20 for outletting effluent. The element 19 typically also comprises an outlet (not shown) for outletting surplus sludge from the

nitrification/denitrification process.

As disclosed herein, the biomass tank 6 is equipped with a light source, which provides light to the photosynthetic organisms (such as but not limited to algae, such as microalgae, cyano bacteria, plants and/or water plants) in order to provide them with light to growth. Such a light source may comprise sunlight as well as a plurality of electric light, LEDs, halogen bulbs or a combination thereof. When other light sources than sunlight are used, the composition of the light (wavelengths and intensity) is preferably selected so as to obtain optimal growth condition for the selected growing photosynthetic organisms e.g. algae, cyano bacteria, plants or water plants. While it is envisaged that light with a predominant wave lengths in the red and blue spectra can assure optimal growth conditions, a selection of wave length composition may be selected according to experiments. In order to allow most - preferably all photosynthetic organisms to receive light, the light source(s), excluding sun light, is (are) arranged on a movable device configured so as to expose the photosynthetic organisms (such as but not limited to algaes, cyano bacteria, plants and/or water plants) in the biomass tank to light.

As mentioned previously it may be desired to remove as much suspended matter as possible by applying a bacterial separation element 12 - it may, however, be difficult to remove all bacteria by applying this element thus, it is envisaged that UV light may be applied before applying the light sources above, simultaneously with the light sources above or after applying the light sources above to reduce the amount of bacteria and in a preferred embodiment reduce the amount of bacteria completely.

The bacteria that work in the bacterial tank usually comes with the wastewater. Depending on the process design and the process conditions there will be a selection between the incoming bacterial species. In addition, the various species of bacteria adapted to the process to ensure its survival in the biological cleaning process. The photosynthetic organisms (e.g. he algae/or water plants) in the biomass tank may be selected so as to perform a treatment of the fluid (i.e. the pre-treated wastewater) coming from the bacterial treatment tank (which may or may not have been passed through a separation element). Without being bound by theory, it is envisaged that the present invention is found to be applicable to treat a high variety of different types of wastewaters (and combinations thereof). Thus, wastewater may be selected from the group consisting of municipal wastewater, water from a dairy industry, process water from industry, agriculture and in general, surface water and combinations thereof. In a preferred embodiment the wastewater is not biologically or chemically treated. In a further embodiment the wastewater may be mechanically treated. Thus, the term non-treated wastewater essentially covers (i) wastewater which has not been subjected to biological or chemical treatment and/or (ii) wastewater which has been subjected to mechanical treatment. The biological treatment may cover nitrification and denitrification whereas the chemical treatment may cover additions of chemicals to enhance sedimentation. It is contemplated that the present invention will be able to treat most kinds of liquid containing biological material as long the biological material is susceptible to degradation by bacterial and photosynthetic organisms (such as but not limited to algae, cyano bacteria, plants and/or water plants) treatment during which two processes CO2 and O2 is produced and "inter recycled" as disclosed herein.

Thus, the present invention is applicable to treat wastewater and the wastewater treated by the present invention comprises biological material susceptible to degradation by bacteria and photosynthetic organisms. In order to obtain degradation by bacteria and/or photosynthetic organisms, limits as to salinity, salt concentration, pH, temperature may be enforced onto the liquids in a system or process according to the invention. While these limits often are defined with reference to a specific set-up of device, waste water, bacteria and photosynthetic organisms (and may be defined by experiments) it is generally found that the pH may preferably be within the range of 6-9 such as approximately 8, and the temperature may preferably be within the range of 5-50°C, such as 10-45 °C, e.g. 15-40°C, 20-35°C, such as 25-30 °C. The salinity may preferably be within 0-3,5 %, such as 0-2 %, e.g. 0-1 %. In the present context, the term salinity and salt concentration are used herein interchangeably.

In an embodiment of the present invention the salinity is adjusted to optimal growth for the photosynthetic organisms grown in the biomass tank during use. Often it is preferred that the content in the bacterial treatment tank and in the biomass tank is mixed typically to assure a homogeneous distribution of the various components in the fluid in the two tanks. In order to provide this, the bacterial tank 5 and the biomass tank 6 each or both comprises an agitator, such as a stirrer, an aerator for introducing gas bubbles, such as air or oxygen enriched gas bubbles or carbon dioxide in a manner where the gas bubbles rises up through the content in the biomass tank.

Reference is made to fig. 3A and 3B illustrating configurations of biomass tanks 6. As illustrated in fig. 3A, a device according to the present invention may comprise a plurality of biomass tanks 6a-6d (four is illustrated in a non-limiting example) between serially connected to each other. The liquid coming either directly from the bacteria treatment tank 5 or from the intermediate bacterial separator 12 is fed into a first biomass treatment tank 6a. After the liquid is treated in the first biomass treatment tank 6a, the liquid is fed into to downstream biomass treatment tank 6b. This is repeated for all the biomass treatment tanks (where four is shown in fig. 3A). As also illustrated in fig. 3A each biomass treatment tank 6 may preferably comprise an outlet 7 for outletting oxygen (O2) as disclosed in connection with fig. 2, which oxygen may be recycled to the bacterial treatment tank 5. The biomass treatment tanks 6a-6d also comprising inlets (not illustrated) for receiving carbon dioxed produced in the bacterial treatment tank 5.

Reference is made to fig. 3B illustrating three parallel coupled biomass tanks 6a, 6b, 6c. As illustrated, the stream coming either directly from the bacteria treatment tank 5 or from the intermediate bacterial separator 12 is divided into sub-streams each being fed into a separate biomass tank 6. The sub-stream may have equal flow rates or different flow rate typically depending on how the bacteria treated wastewater is to be treated by photosynthetic organisms.

Further, the biomass treatment tanks 6a-6c also comprises inlets (not illustrated) for receiving carbon dioxide produced in the bacterial treatment tank 5.

In both the case (parallel or serially coupled) each biomass treatment tank 6 preferably comprises a light source. And, biomass tanks 6 may be applied to grow different algae species, algae in different growth or developmental stages, different water plant species or water plants in different growth or developmental stages in the various tanks. Moreover, the tanks may provide specific growth conditions tailored to the algae and/or water plants present in the tank. By applying such tanks it may also be possible to meet different needs in the industry by being able to provide different photosynthetic organisms (such as algae and/or waterplants) and processed products derived from these photosynthetic organisms (e.g. algae and/or water plants).

Although not illustrated, the bacterial treatment tank 5 may be embodied in a similar manner as a plurality of bacterial treatment tanks 5 either being parallel or serially coupled. A huge advantage of the present invention is that the device may be applied on existing wastewater plants - however, in one embodiment the present invention pertains to a plant comprising a plurality of the devices. The device or a plurality of devices according to the present invention may be configured as stand-alone unit in the sense that no further treatment is needed in order to obtain treated wastewater.

Alternatively, and as mentioned above a device or a plurality of devices according to the present invention may be retro-fitted into existing plants for treating wastewater.

The above description of the invention has focussed on a device for treating waster water. However, as presented above, the invention also relates to a process for treating wastewater. Such a process typically involves the following steps:

pre-treated wastewater 13

carbon dioxide 14

(b) subjecting the pre-treated wastewater to a separation treatment and obtaining at least two fractions, the first fraction comprises a smaller content of suspended matter when compared to the second fraction; and

- feeding the first fraction obtained above to photosynthetic organisms

(d) adding light and at least a fraction of the carbon dioxide 14 obtained by the bacterial treatment, such as aerobic bacterial treatment, and obtaining a biomass of photosynthetic organisms 15

oxygen 16

wherein at least a fraction of the oxygen obtained by the photosynthetic organisms is supplied to the bacterial treatment, such as aerobic bacterial treatment. In a preferred embodiment the invention pertains to a process for treating non- treated wastewater, the process comprising the steps of

(a) subjecting wastewater to an bacterial treatment, such as aerobic bacterial treatment and obtaining

- pre-treated wastewater 13

carbon dioxide 14

(c) subsequently to said bacterial treatment, such as aerobic bacterial treatment, and seperation

feeding the first fraction obtained above to photosynthetic organisms (d) adding light and at least a fraction of the carbon dioxide 14 obtained by the bacterial treatment, such as aerobic bacterial treatment, to the

photosynthetic organisms and obtaining

a biomass of photosynthetic organisms 15

oxygen 16

wherein

at least a fraction of the oxygen obtained by the phosynthtis organisms is supplied to the bacterial treatment, such as aerobic bacterial treatment.

The device according to the present invention and as disclosed above may when in use perform the process of the present invention. Therefore, the embodiments and features disclosed in relation to the device as such and when in use clearly also apply to the process of the present invention.

The separation treatment in step (b) is preferably selected from the group consisting of a membrane filtering, settling, cycloning, a lamella separating, lamella clarification, flotating, a device adapted to provide a chemical separation by use of e.g. inorganic salt, metallic salt or a polymer or a combination thereof.

It may be contemplated that the first fraction obtained in step (b) comprises a content of suspended matter of less than 1 vol. %, such as less than 0.5 vol. %, preferably less than 1 vol. %, such as less than 0.1 vol. % whereas it may be contemplated that the second fraction obtained in step (b) comprises a content of suspended matter more than 1 vol. %, such as more than 5 vol. %.

The biomass obtained in step (d) may be subjected to a separation treatment and obtaining at least two fractions preferably, the content of biomass in the first fraction is less than 1 vol. %, such as less than 0.5 vol. %, such as less than 0.1 vol. %. The separation treatment may be selected from the group consisting of membrane filter, a settler, a cyclone, a lamella separator, lamella clarifier, a flotator, a device adapted to provide a chemical separation by use of e.g.

inorganic salt, metallic salt or a polymer or a combination thereof.

In order to further decrease the content of ammonium and nitrate, the

the first fraction may be subjected to an ammonium/nitrate removal, preferably with microbial nitrification and denitrification, and obtaining an outlet effluent. Whether this step of ammonium/nitrate removal is fact is necessary depends on the composition of the wastewater and the uptake of nutrients by the

photosynthetic organisms in the biomass tank, however applying photosynthetic organisms as a separate step as possible by the present process and by applying the device of the present invention, may make this step of ammonium/nitrate removal superfluous.

Governmental regulations rule the maximum of nutrients allowable in the outlet effluent. It may however be contemplated that the outlet effluent comprises less than than 1 vol. %, such as less than 0.5 vol. %, preferably less than 1 vol. %, such as less than 0.1 vol. % of ammonium/nitrate.

The light source according to the present invention may comprise a plurality of LEDs, halogen bulbs, sun light or a combination thereof. When other light sources than sun light is used, the composition of the light is preferably selected so as to obtain optimal growth condition for the photosynthetic organisms. While it is envisaged that light with a pre-dominant wave length in the red and blue spectra can assure optimal growth conditions, a selection of wave length composition may be selected according to experiments. It may be contemplated to remove as much suspended matter as possible by the separation in step (b) - it may however be difficult to remove all bacteria thus, it is envisaged that UV light may be applied before applying the light sources above, simultaneously with the light sources above or after applying the light sources above to reduce the amount of bacteria and in a preferred embodiment reduce the amount of bacteria completely.

The bacteria performing the bacterial treatment is typically selected based on the wastewater to be treated. The actual selection of bacteria or a group of bacteria may vary based on the composition of the wastewater and also e.g. with the season. While it is contemplated that the selection of bacteria is within the reach of a skilled person, experiments can be carried out to select the bacteria.

Typically, such experiment - or in general the selection - aims at selecting bacteria which pre-treat the wastewater according to pre-defined criteria as to speed of treatment and conversion rate.

The photosynthetic organisms (such as algae and/or water plants) to which the first fraction is feed may similarly be selected so as to optimally grow and generate biomass based on the composition of the first fraction.

The wastewater may be selected from the group consisting of municipal wastewater, water from a dairy industry, process water in general, surface water and combinations thereof. In a preferred embodiment the wastewater is not biologically or chemically treated. In a further embodiment the wastewater is mechanically treated. Thus, the term non-treated wastewater essentially covers (i) wastewater which has not been subjected to biological or chemical treatment and/or (ii) waterwater which has been subjected to mechanical treatment. The biological treatment may cover nitrification and denitrification whereas the chemical treatment may cover addition of chemicals to enhance sedimentation. It is contemplated that the process of present invention will be able to be applied on most kinds of liquid containing biological material as long the biological material is susceptible to degradation by bacterial and algae treatment during which two processes CO2 and O2 is produced and "inter recycled" as disclosed herein. Thus, the wastewater treated/processed by the present invention comprises biological material susceptible to degradation by bacteria, photosynthetic organisms (e.g. algae and/or water plants) and certain limits as to salinitet, salt concentration, pH, temperature may be enforced onto the liquids in a system according to the invention. Without being bound by theory, it is contemplated that the pH will be within the range of 6-9 such as approximately 8, and the

temperature will be within the range of 5-50°C, such as 10-45 °C, e.g. 15-40°C, 20-35°C, such as 25-30 °C. The salinity may preferably be within 0-3,5 %, such as 0-2 %, e.g. 0-1 %. In the present context the term salinity and salt concentration are used herein interchangeably.

In an embodiment of the present invention the photosynthetic organisms (e.g. algae and/or water plants) is grown in a plurality of serially fluidic connected biomass tanks (6a-6d) and obtaining photosynthetic organisms (e.g. algae and/or water plants) in various growth stages or photosynthetic organisms (e.g. algae and/or water plants) of various species.

It may be preferred that the algae is grown for at least 1 hours, such as for at least 6 hours, such as for at least 12 hours, preferably for at least 24 hours or even longer.

From this "second fraction" is taken surplus sludge, which is dewatered to a dry solids content of 15 - 25%. On the WWTP digester, this dewatered sludge converted to methane gas. Is the WWTP without digester, the dewatered sludge is spread on agricultural land, sent to an incinerator.

A biomass and use of the biomass

The above process may be applied for production of biomass of photosynthetic organisms, water plant biomass, fertilizers (Ν,Ρ,Κ), a carbon source, lipids, carbohydrates, proteins, bioactive compounds and combinations thereof.

Thus, the invention also pertains to a biomass of photosynthetic organisms obtained by the process of the present invention. The biomass produced from wastewater treatment herein (i.e. the biomass of photosynthetic organisms) described may be further converted to any kind og products within the sectors of energy (e.g. bioethanol, butanol, biogas, syn-gas), biomaterials (e.g. composite materials, fertilizer, textiles, fibers and minerals), chemicals (commodity chemicals, fine chemicals, emulsifiers, detergents, fracking agents, fatty acids, esters and fatty acids, and chemical building blocks), cosmetics and pharmaceuticals (e.g. bioactive counds of sugarpolymers, antioxidants, vitamins, proteins and minerals) and/or food and feed ingredients (e.g. polysaccharides, proteins, vitamins, minerals, antioxidants. Prior to the conversion the biomass, e.g. algae, cyano bacteria, plants or water plants need precondition by dewatering, drying, ensiling, milling etc. and combinations hereof to enabled handling, fractionation and conversion to above mentioned products. It should be noted that embodiments and features described in the context of one of the aspects of the present invention also apply to the other aspects of the invention.

Accordingly, the present invention pertains to the use of the process disclosed above for the production of a biomass comprising photosynthetic organisms, water plants, cyanobacteria or any other plant, fertilizers, a carbon source, carbohydrates, proteins, lipids, bioactive compounds and/or combinations thereof.

All patent and non-patent references cited in the present application, are hereby incorporated by reference in their entirety.

Itemized list of preferred features, embodiments and aspects according to the present invention :

Item 1. A device for treatment of wastewater, the device comprising :

- a bacterial treatment tank (5) having an inlet (10) for receiving wastewater for pre-treating the wastewater by bacterial treatment;

a biomass tank (6) with a light source (4) adapted to expose the content in the biomass tank (6) to light for producing a biomass of photosynthetic organisms and having an outlet (11) for outletting a biomass of

photosynthetic organisms; a first fluid connection (8) and a second fluid connection (7) each connection extend between the bacterial treatment tank (5) and the biomass tank (6);

wherein

- the first fluid connection (8) is adapted to transport C0₂ produced in the bacterial treatment tank (5) from the bacterial treatment tank (5) to the biomass tank (6);

the second fluid connection (7) is adapted to transport oxygen, or oxygen containing gas, produced in the biomass tank (6) from the biomass tank (6) to the bacterial treatment tank (5); and

the bacterial treatment tank (5) is in fluid connection (9) with the biomass tank (6) for receiving at least a fraction of the pre-treated wastewater from the bacterial treatment tank (5). Item 2. A device for treatment of wastewater according to item 1, wherein the fluid connection (9) between the bacterial treatment tank (5) and the biomass tank (6) comprises a bacterial separation element (12) being adapted to receive pre-treated wastewater from the bacterial treatment tank (5), separate the received pre-treated wastewater into at least two fractions, the first fraction comprising a smaller content of suspended matter, compared to the second fraction, the first fraction preferably contains less than 1 vol. %, such as less than 0.5 vol. %, preferably less than 0.2 vol. %, such as less than 0.1 vol. % of suspended matter and adapted to feed the first fraction to the biomass tank (6). Item 3. The device according to item 2, wherein the bacterial separation element (12) comprises an outlet (17) for outletting the second fraction.

Item 4. The device according to item 3, wherein the outlet (17) is connected to the bacterial treatment tank for inletting the second fraction, or at least a part thereof, to the bacterial treatment tank.

Item 5. A device according to items 1-3 where the salinity is adjusted to optimal growth for the photosynthetic organisms grown in the biomass tank during use. Item 6. The device according to any one of the preceding items, wherein the device further comprises an biomass separation element (18) connected to the outlet (11) of the biomass tank (6) for receiving the biomass of photosynthetic organisms.

Item 7. The device according to item 4, wherein the biomass separation element separates the biomass into at least two fractions, the first fraction comprising comprising a smaller content of biomass compared to the second fraction, preferably, the content of biomass in the first fraction is less than 1 vol. %, such as less than 0.5 vol. %, such as less than 0.1 vol. %.

Item 8. A device according to any one of the preceding items, wherein the biomass tank comprises a plurality of serially fluidic connected tanks (6a-6d). Item 9. A plant comprising a plurality of the devices according to any of the preceding items.

Item 10. A process for treating wastewater, the process comprising the steps of

(a) subjecting wastewater to an aerobic bacterial treatment and obtaining

- pre-treated wastewater (13)

carbon dioxide (14)

(c) subsequently to said aerobic bacterial treatment and separation

feeding the first fraction obtained above to photosynthetic organisms (d) adding light and at least a fraction of the carbon dioxide (14) obtained by the aerobic bacterial treatment and obtaining

biomass of photosynthetic organisms (15)

- oxygen (16)

wherein at least a fraction of the oxygen obtained by the photosynthetic organisms is supplied to the aerobic bacterial treatment.

Item 11. The process according to item 10, wherein the biomass of photosynthetic organisms obtained in step (d) is subjected to a separation treatment and obtaining at least two fractions preferably, the content of algae in the first fraction is less than 1 vol. %, such as less than 0.5 vol. %, such as less than 0.1 vol. %.

Item 12. The process according to item 11, wherein the first fraction is subjected to an ammonium/nitrate removal with a microbial nitrification/denitrification process and obtaining an outlet effluent.

Item 14. The process according to any one of items 10-13, wherein the algae and/or water plants is grown in a plurality of serially or parallel fluidic connected biomass tanks (6a-6d) and obtaining photosynthetic organisms in various growth stages.

Item 15. A biomass obtained by the process according to any of the items 10-12. Item 16. Use of the process according to any one of items 10-14 for the production of a biomass of photosynthetic organisms, water plant biomass, cyanobacterial biomass or any other plant derived biomass, fertilizers, a carbon source, carbohydrates, proteins, lipids, bioactive compounds and combinations thereof.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous. List of reference symbols used

1 Stream of wastewater

2 Treated wastewater

3 Treatment facility

4 Light source

5 Bacterial treatment tank

6 Biomass tank

6a-6d Biomass tanks or chambers

7 First fluid connection

8 Second fluid connection

9 Third fluid connection

10 Inlet of bacterial treatment tank

11 Outlet of the biomass tank 6

12 Bacterial separation element

13 Pre-treated wastewater

14 Carbon dioxide

15 Biomass (i.e. biomass of photosynthetic organisms)

16 Oxygen

17 Outlet of separation element

18 Biomass separation element

19 Ammonium/nitrate removal element (bacterial removal)

20 Outlet for outletting effluent

21 Outlet for outletting ammonium/nitrate (bacterial nitrogen removal nitrification and denitrification).

22 Outlet for outletting biomass

Claims

1. A device for treatment of wastewater, the device comprising :

a bacterial treatment tank (5) having an inlet (10) for receiving wastewater such as non-treated wastewater for pre-treating the wastewater by bacterial treatment;

a biomass tank (6) in fluid connection (9) with the bacterial treatment tank

(5) for receiving at least a fraction of the pre-treated wastewater from the bacterial treatment tank (6) and comprising a light source (4) adapted to expose the content in the biomass tank (6) to light for producing a biomass of photosynthetic organisms and an outlet (11) for outletting a biomass of photosynthetic organisms;

wherein

the first fluid connection (8) is adapted to transport C0₂ produced in the bacterial treatment tank (5) from the bacterial treatment tank (5) to the biomass tank (6) so as to feed photosynthetic organisms contained in the biomass tank (6) with CO2 produced by the bacteria;

the second fluid connection (7) is adapted to transport oxygen or oxygen containing gas, produced in the biomass tank (6) from the biomass tank

(6) to the bacterial treatment tank (5) so as to feed bacteria contained in the bacterial treatment tank (5) with oxygen produced by the

photosynthetic organisms.

2. A device for treatment of wastewater according to claim 1, wherein the fluid connection (9) between the bacterial treatment tank (5) and the biomass tank (6) comprises a bacterial separation element (12) being adapted to receive pre- treated wastewater from the bacterial treatment tank (5), separate the received pre-treated wastewater into at least two fractions, the first fraction comprising a smaller content of suspended matter compared to the second fraction, the first fraction preferably contains less than 1 vol. %, such as less than 0.5 vol. %, preferably less than 0.2 vol. %, such as less than 0.1 vol. % of suspended matter and adapted to feed the first fraction to the biomass tank (6), and wherein the bacterial content in the first fraction is substantially smaller than the bacterial content in the second fraction.

3. The device according to claim 2, wherein the bacterial separation element (12) comprises an outlet (17) for outletting the second fraction.

4. The device according to claim 3, wherein the outlet (17) is connected to the bacterial treatment tank for inletting the second fraction, or at least a part thereof to the bacterial treatment tank.

5. A devise according to claim 1-3 where the salinity is adjusted to ensure optimal growth of the photosynthetic organisms grown in the biomass tank during use.

6. The device according to any one of the preceding claims, wherein the device further comprises an biomass separation element (18) connected to the outlet

(11) of the biomass tank (6) for receiving the biomass of photosynthetic organisms.

7. The device according to claim 4, wherein the biomass separation element (18) separates the biomass into at least two fractions, the first fraction comprising comprising a smaller content of biomass compared to the second fraction, preferably, the content of biomass in the first fraction is less than 1 vol. %, such as less than 0.5 vol. %, such as less than 0.1 vol. %.

8. A device according to any one of the preceding claims, wherein the biomass tank comprises a plurality of serially fluidic connected tanks (6a-6d).

9. A plant comprising a plurality of the devices according to any of the preceding claims.

10. A process for treating waste water, such as non-treated wastewater, the process comprising the steps of

- pre-treated wastewater (13) carbon dioxide (14)

photosynthetic organisms and obtaining

a biomass of photosynthetic organisms (15)

oxygen (16)

wherein

at least a fraction of the oxygen obtained by the photosynthetic organisms is supplied to the bacterial treatment, such as aerobic bacterial treatment.

11. The process according to claim 10, wherein the biomass of photosynthetic organisms obtained in step (d) is subjected to a separation treatment and obtaining at least two fractions preferably, the content of photosynthetic organisms in the first fraction is less than 1 vol. %, such as less than 0.5 vol. %, such as less than 0.1 vol. %.

12. The process according to claim 11, wherein the first fraction is subjected to an ammonium/nitrate removal with a microbial nitrification/denitrification process and obtaining an outlet effluent.

13. The process according to any one of claims 10-12, wherein the photosynthetic organisms are grown in a plurality of serially or parallel fluidic connected biomass tanks (6a-6d) and obtaining photosynthetic organisms in various growth stages.

14. A biomass obtained by the process according to any of the claims 10-13

15. Use of the process according to any one of claims 10- 14 for the production of a biomass comprising photosynthetic organisms, water plants, cyanobacteria or any other plant, fertilizers, a carbon source, carbohydrates, proteins, lipids, bioactive compounds and/or combinations thereof.