ES2977208B2 - WATER TREATMENT SYSTEM - Google Patents

Description

DESCRIPTION

WATER TREATMENT SYSTEM

TECHNICAL SECTOR

The present invention falls within the field of water treatment, specifically in relation to equipment used for the cultivation of microorganisms for the disinfection and reuse of water. It comprises a collection tank, a bioreaction tank, a filter tank, and a sedimentation tank, where the bioreaction tank comprises a motor for driving the rotation of a paddle wheel, including a frequency inverter.

BACKGROUND OF THE INVENTION

Having quality water is essential for human health and environmental protection. However, human activities inevitably generate wastewater, and therefore, wastewater treatment is an unavoidable necessity for all citizens and public administrations. Treatment refers to measures aimed at reducing the content of pollutants present to levels compatible with discharge into natural bodies of water, such as rivers.

Currently, agglomerations with an equivalent population of more than 2,000 inhabitants have widely known treatment systems. However, those with an equivalent population of less than 2,000 inhabitants are the group of agglomerations that require the greatest level of intervention, since, due to the small size of the municipalities and localities that comprise them, the resources to adequately treat their water are very limited. Conventional treatment plants have high investment costs, and installing these plants on a small scale would not be viable.

The sanitation and water treatment of these population centers presents a series of unique characteristics that differentiate medium- and large-sized towns from small towns. These differences are primarily related to the characteristics of their water flows and/or pollutant loads.

Of particular relevance is the scale factor, which penalizes the possible treatments employed. The smaller the population, the higher the cost per inhabitant, which is sometimes difficult to manage. This fact, combined with the large seasonal fluctuations in generation, even hourly, means that treatment in small towns must be tailored specifically. Furthermore, small towns are generally characterized by generating a small volume of wastewater, but it is highly contaminated.

It is also worth mentioning that the United Nations Summit's objective has always been to "Ensure environmental sustainability," setting the goal of "halving the proportion of the population without sustainable access to drinking water." The World Health Organization (WHO), in its document "WHO Guidelines for the Safe Use of Wastewater, Excreta, and Greywater," links the Millennium Development Goals to water reuse. It considers water reuse a strategic resource of particular value in areas experiencing water stress, as long as public health and environmental protection are ensured. It points out the following advantages: reduced pressure on the resource, reduced health risks for downstream users, and maintenance of ecosystem quality. According to the UN, the world's population is expected to reach 8.5 billion by 2030. This figure means that by then, 60% of the world's population will have difficulty accessing the essential resource of water. Biological contamination resulting from livestock and domestic activities turns waterways into vehicles for pathogens that can cause disease. It is estimated that 840,000 people worldwide died from consuming contaminated water in 2012.

Commercial elimination mechanisms are typically based on complex physical-chemical processes: advanced oxidation with catalysts, photocatalysis, ozonation, nanofiltration, ultraviolet irradiation; or traditional chlorination, which can lead to the formation of organochlorines with significant environmental and human health impacts. In turn, all of these methods have high energy and operational costs. These processes' dependence on non-renewable resources makes them less desirable from an environmental sustainability perspective.

Thus, in light of all the above, there is a growing need to develop a new system for treating water, whether it comes from agricultural or livestock sources, industrial sources, or urban waste, and for reusing it for agricultural and environmental purposes.

EXPLANATION OF THE INVENTION

The present invention relates to a non-conventional alternative system for the purification and elimination of pathogens in domestic and/or agro-industrial wastewater to comply with Royal Decree 1620/2007, which regulates the legal regime for the reuse of treated water.

Previous research has focused on studying the capacity of microalgae to purify wastewater and reduce contaminants, thereby purifying water with pathogen levels suitable for use in irrigation systems. This will achieve water efficiency for drinking water irrigation in areas of water scarcity.

In this context, the search for disinfection methods based on low-cost technologies, such as microalgae disinfection using solar energy as a source for photosynthetic activity, offers an attractive alternative for generating pathogen-free water that can be reused. As a global result, the proposed technology reduces the cost of disinfection processes and their impact on the environment and public health, as well as water demand, allowing the reuse of previously unusable water and reducing resource depletion in primary sectors. Furthermore, microalgae act as a CO2 sink, mitigating the effects of greenhouse gases on climate change.

The elimination of biological contamination indicators that may pose a public health risk is a fundamental step in water reuse. The parameters to be monitored are primarily intestinal nematodes, Escherichia coli, suspended solids, and turbidity. The first two are microbiological indicators, and the other two are physical and chemical indicators. Likewise, and depending on the type of application or destination of the reclaimed water, the reuse RD recommends monitoring other parameters, such as Legionella spp., in the event of aerosolization, or total nitrogen and phosphorus in the case of aquifer recharge or filling ponds at risk of eutrophication.

Conventional wastewater treatment in wastewater treatment plants consists of a series of physical, chemical, and biological processes that remove contaminants from the water for its subsequent discharge into the river. Reused water refers to water that, having been used by the source of the water, has undergone the purification process or processes established in the corresponding discharge permit and those necessary to achieve the quality required for a new private use, depending on the intended uses before its return to the public water and maritime land domains.

Microalgae cultivation is a system that can aid in wastewater treatment, as wastewater is a suitable substrate for microalgae development, as it contains all the nutrients necessary for their growth, such as nitrogen, phosphorus, and potassium present in the water. Microalgae reproduce in the culture medium thanks to the photosynthetic activity they carry out through solar radiation. Microalgae are capable of eliminating microorganisms present in the water, as they are able to live in a culture medium with a high pH, around pH 11, where other microorganisms cannot survive. Furthermore, microalgae generate substances that inhibit the growth of other microorganisms in their culture medium.

The present invention aims to promote the economy and sustainable development, resulting in a study of an alternative disinfection technology that is low-cost, low-energy, produces minimal or no waste, and is environmentally friendly. It also seeks to determine the levels of elimination of potentially dangerous organisms and the energy and resource demands of the process.

More specifically, the water treatment system comprises a collection tank, a bioreaction tank connected to the collection tank, a filter tank connected to the bioreaction tank, and a sedimentation tank connected to the filter tank, where the bioreaction tank comprises a motor for driving the rotation of a paddle wheel, where the motor comprises a frequency inverter for regulating its rotation speed. Said motor with the paddle wheel is necessary to circulate the water through the bioreaction tank, and the frequency inverter provides the ability to adapt the rotation speed to the conditions and state of the water, so that, for example, the microalgae are kept in suspension at a certain density, for a good degree of photosynthetic activity.

Thus, compared to other existing solutions, the system of this invention offers lower energy consumption than other treatments. It also absorbs CO2 through microalgae cultivation, thus generating lower greenhouse gas emissions and being more environmentally friendly. Furthermore, it achieves high levels of purification without the use of chlorinated compounds. It entails lower investment and plant operation costs and therefore requires less maintenance than other conventional treatment plants.

It should also be noted that the terms used are equivalent to others also used in the water treatment technology sector. Specifically, the term "capture tank" would be equivalent to "buffer tank," the term "bioreaction tank" would be equivalent to "photobioreactor," and the term "filter tank" would be equivalent to "constructed wetland."

According to another aspect of the invention, the material of the collection tank is dark-colored polyethylene plastic, preferably black, to achieve greater temperature absorption and maintain the internal heat in the substrate to be degraded by the anaerobic bacteria. This results in greater bacterial activity in the anaerobic digestion process, and consequently, greater removal of organic matter.

Preferably, the collection tank is a rectangular Imhoff tank, divided into several chambers with different functions, including at least one each of a sedimentation chamber, a sludge digestion chamber, a ventilation chamber, and a scum accumulation chamber. This type of tank is characterized, in addition to receiving wastewater, by processing this water through anaerobic digestion pretreatment of the settled sludge. This achieves greater wastewater removal when the contaminant concentration is high.

By dividing the tank into chambers with different functions, primary settling is possible prior to biological treatment. This improves the subsequent biological process, as it allows for peak flow rates to be regulated, allowing for digestion of the settleable solids in the tank, and the sludge that settles out, which is recirculated into the Imhoff tank. Additionally, the BOD5 associated with the settleable solids is eliminated, achieving the following performance with this treatment: elimination of 30% of the BOD5 carried by the influent, and elimination of 60% of the suspended solids. BOD5 refers to the amount of oxygen consumed by bacteria and other tiny living organisms over five days at a temperature of 20°C in a water sample.

In a preferred embodiment of the invention, the bioreaction tank is horizontally elongated and comprises at least one curved side end, a horizontal central partition wall, and a plurality of curved baffles, concentric to each other and concentric with respect to the curved side end. The bioreaction tank or photobioreactor is specifically configured for the cultivation of microalgae, with the concentric baffles serving to direct the water flow and facilitate the return of the water flow through the opposite channel.

More specifically, the paddle wheel is located at the exit of the curved side end, in an area with greater depth than the rest of the bioreation tank. This allows the paddle wheel to operate with greater clearance, minimizing the risk of a potential blockage against the bottom due to the accumulation of debris or sludge. It also allows the paddles to be longer, and therefore greater thrust and water circulation capacity, which would have less friction against the sides of the bioreation tank, as it faces a straight section.

Optionally, the blades are made of steel or fiberglass-reinforced plastic, providing high mechanical strength, while, in the latter case, being lighter and less expensive.

Additionally, the filter tank includes a surface waterproofed with polyethylene plastic sheets, thus preventing possible leaks due to its waterproofing qualities, resistance to attack by chemical agents, UV rays, acid impact, and extreme temperatures.

Additionally, the filter tank comprises a soil substrate on the waterproofed surface, intended for growing plants, and on top of said soil substrate it comprises a layer of sand with plant remains, in order to achieve high filtration and moisture retention.

In more detail, these filter tank plants are of the species Scirpus holoschoenus and/or Phragmites australis.

It should also be noted that the sedimentation tank is cylindrical and is topped at its lower base with an inverted cone, so that its own geometric configuration leads to better collection and storage of sediments at one point.

Advantageously, the sedimentation tank comprises a galvanized sheet metal wall, offering increased corrosion resistance.

In addition, the sedimentation tank comprises a wall of opaque fiberglass, thus preventing the entry of light.

Furthermore, the sedimentation tank includes an inlet at the top for water coming from the filter tank, so that the inlet of water does not interfere with the sedimentation process inside the filter tank.

Additionally, the sedimentation tank comprises a first outlet at the top for the generated purified water.

Additionally, the sedimentation tank includes a second outlet at the bottom for the evacuation of sedimented organic matter, with high nutrient content.

The accompanying drawings show, by way of non-limiting example, a water treatment system constructed in accordance with the invention. Other features and advantages of said water treatment system, object of the present invention, will become apparent from the description of a preferred, but not exclusive, embodiment, illustrated by way of non-limiting example in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

To complement the description being made and in order to help better understand the characteristics of the invention, a set of drawings is attached as an integral part of said description, in which the following has been represented for illustrative and non-limiting purposes:

Figure 1 - Side view of the water treatment system, according to the present invention.

Figure 2 - Schematic view of the water treatment system, according to the present invention.

Figure 3A - Plan view of the bioreaction tank of the water treatment system, according to the present invention.

Figure 3B - Side view of the bioreaction tank of the water treatment system, according to the present invention.

PREFERRED EMBODIMENT OF THE INVENTION

In view of the aforementioned figures and, in accordance with the numbering adopted, one can observe in them a preferred embodiment of the invention, comprising the parts and elements indicated and described in detail below.

Figure 1 shows a side view of the water treatment system (1), including a collection tank (2) with a plurality of chambers (21), a bioreation tank (3) with at least one wheel (32) with blades (32a), a filter tank (4), and a sedimentation tank (5), which comprises a lower base (51) with an inverted cone (52), a wall (53) with a lower part (54) and an upper part (55), where an inlet (56) and a first outlet (57) are included. On the contrary, the second outlet (58) is located in the lower part of the inverted cone (52).

Figure 2 shows a schematic view of the water treatment system (1), showing the collection tank (2), the bioreaction tank (3), the filter tank (4), with its waterproofed surface (41), on which a substrate (42) with at least one plant (43) is placed, which will give rise to a layer (44) of plant remains (45). A sedimentation tank (5) can also be seen with its inlet (56), a first outlet (57) and a second outlet (58).

In figure 3A a plan view of the bioreation tank (3) of the water treatment system (1) can be seen, where the bioreation tank (3) includes a motor (31) with its frequency converter (31a), coupled to a wheel (32) with its blades (32a) in a specific area (35), a central partition (33), and at least one lateral end (34) with its deflectors (34a).

In Figure 3B you can see a side view of the bioreaction tank (3) of the water treatment system (1), including at least one wheel (32) with its plurality of blades (32a).

It should be noted that, preferably, the bioreation tank (3) is a raceway-type lagoon, with an oval shape, which is built on the ground with a water surface of 25 to 30 cm high, a large surface area, and a central partition (33) forming two channels through which the water (1) will circulate with the algae. The lagoon is fed by pumping the wastewater (1) to be treated. The algae reproduce and feed on the polluting compounds in the water (1). With retention times ranging from 6 to 12 days, an adequate reduction in the concentration of the pollutants in the effluent water (1) is achieved. The outlet of the bioreation tank (3) is by overflow and is directed, after passing through the filter tank (4), to the sedimentation tank (5) where the algar biomass thickens by decantation and is separated from the effluent, which is the purified water (1).

More particularly, as seen in Figures 1 and 2, the water treatment system (1) comprises a collection tank (2), a bioreaction tank (3) connected to the collection tank (2), a filter tank (4) connected to the bioreaction tank (3), and a sedimentation tank (5) connected to the filter tank (4), where the bioreaction tank (3) comprises a motor (31) to drive the rotation of a wheel (32) of blades (32a) where the motor (31) comprises a frequency converter (31a) to regulate its rotation speed.

In an embodiment of the invention, the bioreation tank (3) is provided with a wheel (32) with eight flat blades (32a), which is an effective means of producing water flow (1) in the pond. Said system is located at the exit of the curve at the lateral end (34) of the lagoon, with the wheel (32) located in an area (35) with greater depth than the rest of the lagoon, on the order of 8 to 12 cm, and adjusted to the circular shape of the wheel (32), leaving a safety margin of 2 to 4 cm. In this way, greater efficiency of movement transmission between the blade (32a) and the water (1) is guaranteed. The total height of each blade (32a) is approximately 0.45 to 0.55 m, and the diameter of the wheel (32) is 0.90 to 1.10 m. The blades (32a) must be supported on the shaft in such a way that they do not bend due to the pressure of the water (1) during rotation. The motor (31) has a nominal power of 2.0 to 2.4 kW, and is equipped with a frequency converter (31a) to modulate its speed. This system produces a linear speed of water circulation (1) between 0.15 and 0.5 m/s. As for the sedimentation tank (5) for collecting the algal biomass, it has a cylindrical shape ending in an inverted cone (52) at its lower base (51), with an approximate volume of 5 m3, a diameter of 1.62 m and a height of 3.5 m, allowing the biomass to be settling by gravity.

Optionally, as seen in figures 1 and 2, the material of the collection tank (2) is dark-colored polyethylene plastic.

Additionally, as can be seen in Figure 1, the collection tank (2) is a rectangular Imhoff tank, divided into a plurality of chambers (21) with different functions.

On the other hand, as seen in Figure 3A, the bioreation tank (3) is horizontally elongated and comprises at least one curved side end (34), a horizontal central partition (33), and a plurality of curved baffles (34a), concentric to each other and concentric with respect to the curved side end (34). As mentioned, the bioreation tank (3) is a raceway-type lagoon, in the form of an elongated carousel, whose channels have a depth of 0.5 to 0.7 m, of which between 0.25 and 0.35 m contain recirculating water. The total dimensions are approximately 130 m long and 11 meters wide, resulting in a total surface area of 1500 m2 and an effective volume of 310 to 330 m3. The central partition (33), optionally 1 m thick, divides the lagoon into two channels of identical surface area. The entire lagoon will be constructed from compacted earth.

Preferably, as shown in Figures 3A and 3B, the wheel (32) with blades (32a) is located at the exit of the curved lateral end (34), in an area (35) with greater depth than the rest of the bioreaction tank (3). Preferably, it comprises a single wheel (32) with eight flat blades (32a).

More specifically, as seen in Figures 3A and 3B, the material of the blades (32a) is steel or fiberglass reinforced plastic.

On the other hand, as can be seen in Figure 2, the filter tank (4) comprises a waterproofed surface (41) with insulating polyethylene plastic sheets of 1 to 2 mm thickness. Said filter tank (4) is also horizontally elongated and comprises at least one curved side end (34), that is, in the form of an elongated carousel.

In more detail, as can be seen in Figure 2, the water treatment system (1) comprises on the waterproofed surface (41) a substrate (42) of soil, intended for the cultivation of plants (43), and on said substrate (42) of soil it comprises a layer (44) of sand with plant remains (45), which are preferably wood chips.

It is worth mentioning that, as seen in Figure 2, the plants (43) are of the species Scirpus holoschoenus and/or Phragmites australis.

In a preferred embodiment of the invention, as seen in Figures 1 and 2, the sedimentation tank (5) is cylindrical and is finished at its lower base (51) with an inverted cone (52). It should be noted that the cylindrical shape has a height/diameter ratio of 4 to 5, which favors the separation of the algal biomass from the effluent water (1). Since the microalgae slowly precipitate on the lower base (51), a height is required that favors the separation by gravity of these microalgae with the effluent water (1), where said lower base (51) has an inverted cone shape (52) that favors the collection of the microalgal biomass.

Additionally, as can be seen in figures 1 and 2, the sedimentation tank (5) comprises a wall (53) of galvanized sheet metal, this being a corrosion-resistant material.

On the other hand, as can be seen in figures 1 and 2, the sedimentation tank (5) comprises a wall (53) of opaque fiberglass.

In more detail, as can be seen in figures 1 and 2, the sedimentation tank (5) comprises an inlet (56) in the upper part (55) for the water (1) coming from the filter tank (4).

Additionally, as seen in figures 1 and 2, the sedimentation tank (5) comprises a first outlet (57) in the upper part (55) for the purified water (1) generated.

Additionally, as can be seen in figures 1 and 2, the sedimentation tank (5) comprises a second outlet (58) in the lower part (54) for the evacuation of the sedimented organic matter.

The details, shapes, dimensions and other accessory elements, as well as the components used in the implementation of the water treatment system (1), may be conveniently replaced by others that are technically equivalent, and do not depart from the essence of the invention or the scope defined by the claims included after the following list.

List numerical references:

1 water

2 collection tank

21 cameras

3 bioreaction tank

31 engine

31 to frequency inverter

32 wheel

32nd blades

33 central partition

34 side end

34a deflectors

35 zone

4 filter tank

41 waterproofed surface

42 substrate

43rd floor

44 layer

45 plant remains

5 sedimentation tank

51 lower base

52 inverted cone

53 wall

54 bottom

55 top

56 entry

57 first exit

58 second exit

Claims (1)

1- Water treatment system (1) comprising a collection tank (2), a bioreation tank (3) connected to the collection tank (2), a filter tank (4) connected to the bioreation tank (3), and a sedimentation tank (5) connected to the filter tank (4), characterized in that the bioreation tank (3) comprises a motor (31) to drive the rotation of a wheel (32) of blades (32a) where the motor (31) comprises a frequency converter (31a) to regulate its rotation speed. 2- Water treatment system (1), according to claim 1, characterized in that the material of the collection tank (2) is dark-colored polyethylene plastic. 3- Water treatment system (1), according to any of the preceding claims, characterized in that the collection tank (2) is a rectangular Imhoff tank, divided into a plurality of chambers (21) with different functions. 4- Water treatment system (1), according to any of the preceding claims, characterized in that the bioreaction tank (3) is horizontally elongated and comprises at least one curved lateral end (34), a horizontal central partition (33) for separation, and a plurality of curved deflectors (34a), concentric with each other and concentric with respect to the curved lateral end (34). 5- Water treatment system (1), according to any of the preceding claims, characterized in that the paddle wheel (32) (32a) is located at the exit of the curved lateral end (34), in an area (35) with greater depth than the rest of the bioreation tank (3). 6- Water treatment system (1), according to any of the preceding claims, characterized in that the material of the blades (32a) is steel or fiberglass reinforced plastic. 7- Water treatment system (1), according to any of the preceding claims, characterized in that the filter tank (4) comprises a waterproofed surface (41) with polyethylene plastic sheets. 8- Water treatment system (1), according to claim 7, characterized in that on the waterproofed surface (41) it comprises a substrate (42) of soil, intended for the cultivation of plants (43), and on said substrate (42) of soil it comprises a layer (44) of sand with plant remains (45). 9- Water treatment system (1), according to claim 8, characterized in that the plants (43) are of the species Scirpus holoschoenus and/or Phragmites australis. 10- Water treatment system (1), according to any of the preceding claims, characterized in that the sedimentation tank (5) is cylindrical and is finished at its lower base (51) with an inverted cone (52). 11- Water treatment system (1), according to claim 10, characterized in that the sedimentation tank (5) comprises a wall (53) of galvanized sheet metal. 12- Water treatment system (1), according to claim 10, characterized in that the sedimentation tank (5) comprises a wall (53) of opaque fiberglass. 13- Water treatment system (1), according to any of the preceding claims, characterized in that the sedimentation tank (5) comprises an inlet (56) in the upper part (55) for the water (1) coming from the filter tank (4). 14- Water treatment system (1), according to claim 13, characterized in that the sedimentation tank (5) comprises a first outlet (57) in the upper part (55) for the purified water (1) generated. 15- Water treatment system (1), according to any of claims 13 or 14, characterized in that the sedimentation tank (5) comprises a second outlet (58) in the lower part (54) for the evacuation of the sedimented organic matter.