WO2018182435A1

WO2018182435A1 - Biological wastewater treatment plant

Info

Publication number: WO2018182435A1
Application number: PCT/PL2017/050017
Authority: WO
Inventors: Andrzej Golcz
Original assignee: Andrzej Golcz
Priority date: 2017-03-29
Filing date: 2017-03-29
Publication date: 2018-10-04
Also published as: PL431332A1

Abstract

The invention relates to a biological wastewater treatment plant operating in two parallel and independently operating lines in a continuous flow system. The wastewater is subjected to the stages of removing contaminations, and each of the lines has optionally selected equipment, such as the dephosphorisation chamber (7, 7'), the denitrification chamber (8, 8') and the nitrification chamber (9, 9'), as well as a chamber for additional denitrification and removal of the remains of easily accessible carbon connected to a vacuum degassing tower (24'), and a secondary sedimentation tank (1) with an outflow of purified wastewater, which is connected to the inflow of sludges into the dephosphorisation chamber (7, 7') by external recirculation of a sediment sludge. The tank has convergent sidewalls, and on its bottom, in the well (13), sediment sludge accumulates. According to the invention, the elements of each of the two parallel and independently operating lines (3, 3') of the wastewater treatment plant are placed outside of the secondary sedimentation tank (1) and generally adjacent to the mantle (5) of the secondary sedimentation tank (1), and each of these two lines is connected to one shared node, comprising a vacuum degassing tower (24) and an additional denitrification chamber (23). The secondary sedimentation tank (1) is divided by a partition (10), in the form of a vertical wail into two zones (A, B) of secondary sludge sedimentation, each of these zones (A, B) having an independent well (13, 13') for the collection of sludges sedimenting on the bottom (2) of the secondary sedimentation tank (1) and recirculated in the beginning of the wastewater treatment process, in the wastewater treatment plant according to the invention the anaerobic processes are conducted in marked chambers under the bottom of the sedimentation tanks. The facility of the wastewater treatment plant of the invention is highly compact.

Description

BIOLOGICAL WASTEWATER TREATMENT PLANT

The invention relates to a wastewater treatment plant carrying out a processes of the biological treatment of wastewater in two parallel and independently operating lines, operating in a continuous flow system.

Patent specification US 9,499,424 B2, according to WO2014/077711 [PCT/PL2013/000144], granted in the name of the inventor of the present solution, discloses a method and installation for wastewater treatment of in a flow system.

There are well known and generally commonly used wastewater treatment plants carrying out the processes of biological wastewater treatment in two or more lines, operating in parallel and independently, working in a continuous flow system, in which wastewater is subjected to stages of removing various forms of contaminations contained in wastewater. Each of the parallel and independently operating lines has equipment selected optionally from elements such as a dephosphorisation chamber, a denitrification chamber and a nitrification chamber, from which there is a recirculation- return connection with the denitrification chamber, as well as a chamber for additional denitrification and removal of the remains of easily accessible carbon, connected to a vacuum degassing tower, possibly to a suction well, as well as a secondary sedimentation tank with the outflow of purified wastewater and connected to the inflow of a sludge to the dephosphorisation chamber by external recirculation of the sediment sludge. The secondary sedimentation tank has the form of a tank, on its bottom there is a well where the sediment sludge accumulates.

in the process of biological wastewater treatment by means of activated sludge, the purified wastewater, which after the treatment process is a mixture of activated sludge in the already purified wastewater, is subjected to division in a process of gravitational sedimentation into a stream of purified wastewater and a stream of deposited, sedimenting, concentrated sludge, collected from the sedimentation tank bottom, returned back again to the treatment process.

Sedimentation performed in secondary sedimentation tanks having generally cylindrical shapes is a process of the gravitational precipitation of activated sludge on sedimentation tank bottoms, occurring in parallel flow or counter flow, like in vertical sedimentation tanks in relation to the flow of wastewater.

The wastewater treatment process, in which a secondary sedimentation tank is its last technical element, is usually conducted in two or numerous treatment lines operating in parallel, which enables the operational emptying of one of them for repairing or operation maintenance.

A sediment sludge, in relatively small sedimentation tanks 1 with a radial shape, as shown in fig. 1 and fig. 2 presenting the known solutions, slides in accordance with the arrows along the surface of a sludge hopper 11 , surrounded by a mantle 5 and delimited by a conical wall, into the well 13 collecting the sludges sedimenting on the bottom 2 of the sedimentation tank 1. From the well 13, as a return sludge, this sediment sludge is again directed into the treatment process.

In the cases of larger sedimentation tanks, a sludge is scraped into wells from a flat or inclined bottom by scraping or sucking devices, operating in a continuous or periodic rotary motion, scraping the sludges accumulated at the bottom to a centrally positioned well. From the central well the sludges are subsequently directed to be reused in the process.

Realising wastewater treatment plant lines operating in parallel, particularly when using radial or vertical sedimentation tanks, requires a large area and considerable expenditures.

Such wastewater treatment plants, particularly in a cold climate or close to a built-up area or for other reasons, often require placing them below a cover, which considerably increases the costs of realisation and operation.

Practical implementation of this type of wastewater treatment plant, as well as other known wastewater treatment plants, requires a necessary access to areas of large surface. The costs of erecting the individual facilities of the treatment plant are considerable, and the additional costs of realising the fencing of treatment plant facilities and their supervision during operation, due to their size, have a significant impact on the total operating costs incurred over the whole lifetime of the treatment plant. Sedimentation tanks in the form of generally cylindrical tanks with a vertical flow, in which the sedimentation of wastewater occurs, are also known, in these sedimentation tanks the wastewater flows in a counter flow, mostly upwards, which is shown by arrows in fig. 2, into troughs receiving the purified wastewater, and the sludge precipitates along the conical surfaces of the sludge hopper to the bottom, from which it is received for reuse in the treatment process.

Sedimentation tanks of this type, due to their practical possibility of use resulting from the construction-related, cost-related and technical-operational problems, as weli as the characteristics of the activated sludge, are used to a depth H of approximately 9 metres and they are found useful for flows through the sedimentation tank of up to approximateiy 1000 m³/day at sludge concentrations in the process of 3.5 kg dry mass/m³. Such sedimentation tanks may have relatively small diameters only, since their operational depth H is limited to 6÷9 m.

It should be also pointed out that there are known sedimentation tanks, called radial tanks, with circular shape, which have a centrifugal flow, in which the sedimentation of sludge occurs in parallel flow with the flow of wastewater.

These sedimentation tanks are considerably shallower and generally do not exceed a depth of H= 5 metres, and distribution of wastewater occurs in streams horizontally and generally radially (from a central intake) in the overflow directions situated on the perimeter of a circle and collecting the purified wastewater.

In these flow streams a sludge falls to the bottom, from where they are mechanically scraped into a sludge well, from where they are recycled to be reused in the process, wherein in some cases sedimentation tanks with scrapers sucking the sludge from the bottom of the sedimentation tank are used.

Sedimentation tanks of this type are used generally in all wastewater treatment plants of any size, in which wastewater treatment processes are realised in numerous treatment lines and numerous secondary sedimentation tanks, for example in the following conditions:

flow rate 400000 m³/ day,

treatment lines - 5 pieces;

depth H =7.5 m;

sludge concentration 3.5 kg/m³,

secondary sedimentation tanks - 20 pieces;

with a diameter of 50 m and depth H = 4.5 m. The purpose of the present invention is to provide a new biological wastewater treatment plant, exhibiting a considerable degree of compactness, which allows a significant reduction in the costs of its construction and operation, and as a consequence it allows locating such a biological wastewater treatment plant closer to the source of wastewater.

The object of the invention is a biological wastewater treatment plant operating in a continuous flow system in two parallel and independent lines, in which wastewater is fed to consecutive stages of removing various forms of contaminations contained therein, and each of the lines has equipment selected optionally from elements such as a dephosphorisation chamber, a denitrification chamber and a nitrification chamber, from which there is a recirculation-return connection to the denitrification chamber, as well as a chamber for additional denitrification and removal of the remains of easily accessible carbon, connected to a vacuum degassing tower, as well as a secondary sedimentation tank with the outflow of the purified wastewater, connected to the inflow of sludges to the dephosphorisation chamber by external recirculation of a sediment sludge, having the form of a tank with sidewalls convergent towards each other and towards the bottom, the accumulating a sediment sludge being collected on the bottom in the well, characterised in that the elements of each of the two wastewater treatment lines (3, 3_ ) operating in parallel and independently, are positioned outside the secondary sedimentation tank (1) and in the space adjacent to the mantle (5) of the secondary sedimentation tank (1), and each of these two lines (3, 3J) is fed to one shared node, comprising a tower (24) for vacuum degassing and an additional denitrification chamber (23).

The vessel of the secondary sedimentation tank (1) is preferably divided by a partition (10) into two zones (A, B) of secondary sludge sedimentation, each zone (A, B) having an independent well (13, 131) collecting a sediment sludge on the bottom (2) of the secondary sedimentation tank (1) and the sludges are subjected to recirculation at the beginning of the wastewater treatment process. The partition (10) preferably has the form of a vertical wall.

The two zones (A, B) of secondary sludge sedimentation are preferably equal.

The wells (13, 13') collecting sediment sludge is preferably placed in direct vicinity to the partition (10), preferably close to the vertical axis of symmetry of the secondary sedimentation tank (1), and the wells (1_3, 13J) are preferably placed each at a distance (14) on each of the two sides of the partition Q0). Preferably, each of the wells (13, 13') collecting the sludges sedimenting on the bottom (2) of the sedimentation tank constitutes the bottom end of conically shaped zones (A, B).

In the perimeter part of the secondary sedimentation tank (1), generally in the plane of the partition (10), there is preferably placed a wastewater inflow collector (21).

The wastewater inflow collector (21) is preferably shared and it delivers wastewater indirectly via the inflow chamber (22) or directly into the dephosphorisation chamber (7), from which a division into two independent treatment lines operating in parallel (3, 3') occurs. Preferably, the wastewater inflow collector (21) delivers wastewater into the space (7) divided into (7, 7'), each of which is assigned to the corresponding treatment line (3 and 3Ί.

The selected elements of the wastewater treatment plant according to the invention of the two biological wastewater treatment parallel and independently operating lines (3, 3 ) are preferably distributed inside the secondary sedimentation tank (1), in spaces (15, 15') delimited outside the conical walls (U, 11 '), delimiting the zones of secondary sludge sedimentation. Under the secondary sedimentation tank (1) and preferably under the bottom (2) of the secondary sedimentation tank (1) there is a space (25) of anaerobic processing for the stage of denitrification or dephosphorisation. The space

(25) of anaerobic processing is preferably divided by a separating wail (26) into denitrification chambers (8, 8_1) for the individual treatment lines. The separating wall

(26) preferably extends in the space (25) of anaerobic processing diametrically, at the same time serving the function of an element supporting and holding the bottom (2) of the secondary sedimentation tank (1), at the same time constituting the ceiling of the space (25) of anaerobic processing. Preferably, each of the denitrification chambers (8, 8_ ) is divided by labyrinth walls (27) delimiting the flows of wastewater and sludges in this chamber, at the same time additionally serving the function of supporting walls for the bottom (2) of the secondary sedimentation tank (1).

According to the invention, the wastewater treatment plant works in a continuous flow system and realises the processes of biological wastewater treatment. It has two parallel and independently operating lines. In each of these lines the wastewater is subjected to the stages of removing various forms of contaminations contained therein. Each of the parallel and independently operating lines has an equipment selected optionally from elements such as the dephosphorisation chamber, the denitrification chamber and the nitrification chamber, from which there is a recirculation-return connection with the denitrification chamber, as well as a chamber for additional denitrification and removal of the remains of easily accessible carbon, connected to a vacuum degassing tower. Additionally, the treatment plant has a secondary sedimentation tank with the outflow of the purified wastewater, connected to the inflow of sludges into the dephosphorisation chamber by external recirculation of a sediment sludge. The sedimentation tank has the form of a tank with sidewalls convergent towards each other and towards the bottom. The sediment sludge accumulates at the bottom of the sedimentation tank. In its bottom part the sedimentation tank has a well, accumulating a sediment sludge.

The essence of the invention is that the elements of each of the two wastewater treatment parallel and independently operating lines are positioned and generally outside the secondary sedimentation tank adjacent to the mantle of the secondary sedimentation tank, and each of these two lines is connected to one shared node, comprising a vacuum degassing tower and an additional denitrification chamber.

The secondary sedimentation tank is divided by a partition, generally having the form of a vertical wall, into two zones of secondary sludge sedimentation, preferably equal, each of these zones having an independent well collecting the sludges sedimenting on the bottom of the secondary sedimentation tank and recirculated to the beginning of the wastewater treatment process.

The wells collecting a sediment sludge is placed in a direct vicinity of the partition, preferably close to the vertical axis of symmetry of the secondary sedimentation tank.

Alternatively, the wells collecting sediment sludge is placed each on each of the two sides of the partition, at a distance from this partition.

Each of the wells collecting the sediment sludge on the bottom of the sedimentation tank constitutes the bottom end of conically shaped zones.

In the perimeter part of the secondary sedimentation tank, generally in the plane of the partition, there is preferably placed a wastewater inflow collector, separable for each of the independently operating lines.

Alternatively, in the perimeter part of the secondary sedimentation tank, generally in the plane of the partition, there is placed a wastewater inflow collector, shared by the independently operating lines. The selected elements of the two biological wastewater treatment parallel and independently operating lines are also distributed inside the secondary sedimentation tank, in the spaces delimited outside of the conical walls, delimiting the zones of secondary sludge sedimentation, meaning under their bottom.

In sedimentation tanks, particularly those with a radial from, and preferably under the bottom, there is placed a space for anaerobic processing, in which the stages of denitrification, possibly also dephosphorisation, are carried out.

The space for anaerobic processing is divided by a separating wall into denitrification chambers assigned to the individual treatment lines.

The separating wall extends in the space for anaerobic processing diametrically, at the same time serving the function of an element supporting and holding the bottom of the secondary sedimentation tank, at the same time constituting the ceiling of the space for anaerobic processing.

Each of the denitrification chambers is divided by labyrinth walls delimiting the flows of wastewater and sludges in this chamber, at the same time additionally serving the function of supporting walls for the bottom of the secondary sedimentation tank.

The facility of the wastewater treatment plant according to invention is highly compact.

Wastewater treatment plants realised in accordance to the invention occupy a smaller area, require less roads around each of the facilities dismembered as elements carrying out the individual stages of the process in the field, divided by roads, footpaths and technological pipelines/conduits.

Therefore, a biological wastewater treatment plant designed in such a manner is preferable, particularly when there is a shortage of area, a necessary limitation of any environmental impact, and additionally, in particular, in climates which due to low temperatures require the protection of facilities by incorporating them into buildings.

Compacting the wastewater treatment plant in accordance with the invention makes it so that it is generally seif-heating, without the necessity to supply heat from some additional heat source. This creates a possibility of easily covering the treatment plant in the conditions of particularly harsh climatic phenomena, ensuring the operation of the treatment plant from technological platforms placed on the construction of the facility and the devices of the wastewater treatment plant.

Furthermore, using the features of a radial sedimentation tank, namely its smaller depth, and associating this with the possibility to construct activated sludge chambers with a great depth, considerably exceeding the depth of the sedimentation tank using vacuum degassing of sludges, realised along with the additional removal of nitrates, which allows the use of very high concentrations of sludge and great depths of sludge chambers, and ensures the elimination of the disadvantageous impact of this high treating concentration of sludges and the depth of chambers connected to deep process chambers aerating the activated sludge on the operation of secondary sedimentation tanks, it has become possible to use a compact treatment plant complex of high efficiency in one complex of buildings, additionally generating space under the secondary sedimentation tank freed from contact with the environment, for conducting inside thereof an environmentally inconvenient anaerobic treatment process under the bottom of the sedimentation tank, connected to the line of the wastewater treatment process, retaining two treatment lines operating in parallel, in this compact arrangement of the treatment plant with a much smaller area and lower cost of realisation.

Therefore, in the solution according to the invention, an additional wastewater treatment space is introduced, placed under the bottom of the radial secondary sedimentation tank, realising the most environmentally disadvantageous activity of the process of anaerobic treatment technique, with full separation from the contact and impact on the environment, being in a flow and flow- return connection of the internal recirculation of the whole treatment process, retaining two independent treatment lines operating in parallel.

As a result, a compact wastewater treatment plant is achieved, in which around the radial sedimentation tank the treatment process is conducted using the vacuum degassing technology, enabling the use of high concentrations of sludge in the treatment process and the use of a great depth of activated sludge chambers amounting to 9 metres and more, in which the considerable difference in depth between the chambers and the sedimentation tank is used, placing in this fragment of the compact installation the most harmful spaces of anaerobic processes.

It should be noted that generally treatment plants with a depth of H = 5÷6 m are in common use. The use of greater depths resulted in unpreferable operating conditions in the operation of secondary sedimentation tanks, limiting their sedimentation capabilities and causing intense generation of foam on the sedimentation tank surface, as well as difficulties with the sedimentation of sludges. The more this depth was tried to be increased, the greater were the unpreferable results, making the use of such depths more difficult or impossible. The high saturation of liquid with gaseous nitrogen resulting from the process of very deep aeration is reduced by the additional removal of nitrogen in an additional denitrification space connected to the vacuum degassing of sludges. Preferably, this space is realised as a much shallower space and placed by dividing the nitrification space in the final segment of its course. This enables easier elimination of the over- saturation of liquid with nitrogen and improves the operation of vacuum degassing.

Furthermore, due to such solution, the phenomenon of over-saturation of liquid with gaseous nitrogen (dissolved in the liquid), resulting from the aeration of wastewater at a great depth, is eliminated almost entirely. This facilitates the ability to create higher nitrogen deficiency of saturating the liquid flowing into the secondary sedimentation tank in nitrogen by the vacuum tower, eliminating or limiting the flotation phenomena in the sedimentation tanks, in which nitrogen emitted from denitrification occurring in the secondary sedimentation tank, generally in the bottom area of the accumulation of sludge, is not emitted in a gaseous form, but undergoes dissolution in the under- saturation of the liquid in gaseous nitrogen, what eliminates the outflow of sludge and the creation of scum, enabling the use of chambers with depths increased in such manner.

This results in the possibility to use process chambers with great depths and in the lack or a significant limitation of the unpreferable impact on the operation of the secondary sedimentation tanks. At the same time, a dense compact construction has been achieved to realise the wastewater treatment plant with the possibility of using a part of this construction placed under the sedimentation tank for process purposes. In such solution it is possible to practically use a process depth H of 9 m and more.

The object of the invention is shown in drawings, in which

fig. 3 presents the wastewater treatment plant according to the first embodiment, carrying out the processes of biological wastewater treatment in two parallel and independently operating lines , working in a continuous flow system, in a schematic top view,

fig. 4 - the treatment plant of fig. 3 in a schematic vertical cross-section,

fig. 5 - the wastewater treatment plant according to second embodiment, also carrying out the processes of biological wastewater treatment in two parallel and independently operating lines , working in a continuous flow system, in a schematic top view, fig. 6 - the treatment plant of fig. 5 in a schematic vertical cross-section, fig. 7 - the wastewater treatment plant according to third embodiment, also carrying out the processes of biological wastewater treatment in two parallel and independently operating lines , working in a continuous flow system, in a schematic top view, with wells moved away from the wall,

fig. 8 -the treatment plant of fig. 7 in a schematic vertical cross-section,

fig. 9 - the wastewater treatment plant according to fourth embodiment, also carrying out the processes of biological wastewater treatment in two parallel and independently operating lines , working in a continuous flow system, in a schematic vertical cross- section, using a sedimentation tank with radial wastewater flow,

and fig. 10 presents the treatment plant of fig. 9 in a schematic horizontal cross-section along the dashed line, marked in fig. 9.

As shown in fig. 3 and fig. 4, the wastewater treatment plant has a secondary sedimentation tank 1 with a radial shape and the vertical flow of wastewater, limited by a mantle 5, outside of which there are distributed elements of two lines 3, 3' operating in parallel and independently, carrying out wastewater treatment processes in a continuous flow system, closed by a cylindrical outer mantle 6.

Said elements of the lines carrying out wastewater treatment processes may be generally combined arbitrarily, depending on the requirements of the wastewater treatment process.

Typically, in the space delimited by the mantle 5 and the outer mantle 6, there are placed elements such as the dephosphorisation chamber 7, 7', the denitrification chamber 8, 8' and the nitrification chamber 9, 9'.

It is apparent and known in state of the art that nitrification chambers 9, 9' have a recirculation-return connection with the denitrification chamber 8, 8'.

Each of the two lines carrying out wastewater treatment processes is connected to a shared chamber 23 of additional denitrification and removal of the remains of easily accessible carbon, preferably connected to one tower 24 for vacuum degassing shared by both lines.

It is also apparent that the secondary sedimentation tank 1 is provided with an outflow of the purified wastewater Z and it is connected to the inflow of sludges into dephosphorisation chambers 7, 7' by internal recirculation of the sediment sludge V.

The secondary sedimentation tank 1 has a sludge hopper 11 (fig. 4) delimited by a conical wall, ended from the bottom with a weil 13 collecting the sediment sludge on the bottom 2 of the sedimentation tank and recirculated to the beginning of the wastewater treatment process.

It has been assumed that the semi-annu!ar recesses 5 and 15' under the conical walls of the sludge hopper 11 can constitute spaces for conveniently placing in them ail or selected elements of lines 3, 3' carrying out the wastewater treatment processes, if the spaces between the mantle 5 of the sedimentation tank and the outer mantle 6 are not sufficiently capacious. In practice, this means that during both aerobic and anaerobic processing the process is conducted under the skewed conical bottom of the secondary sedimentation tank.

Adjacent to the mantle 5 of the secondary sedimentation tank 1 there are semi-annular troughs 17, 17' placed on the outer side for the internal recirculation of denitrification with a flow directed in accordance with the arrows X. From the inner side of the sedimentation tank mantle 5 the troughs 16 are outflow troughs for purified wastewater or arbitrarily placed conduits.

The arrows Y denote the directions of the flow of wastewater through walls in the space delimited by the mantle 5 and the outer mantle 6, while the arrows Z denote schematically the outflow of the purified wastewater from the semi-annular troughs 16, 16' of the inner sedimentation tank wall.

Raw wastewater intended to undergo treatment is delivered from collector 21 into chamber 22. Sludges, as recirculated materials V from the secondary sedimentation tank 1 , are also delivered into the chamber 22. Furthermore, from chamber 22 a mixture of raw wastewater and recirculating sludges is distributed into the above-mentioned two biological wastewater treatment parallel and independently operating lines 3, 3', which is denoted by arrows Y, Y\

A chamber 23 for the additional removal of nitrates and vacuum degassing of sludges is placed generally opposite, diametrically in relation to the chamber 22, realised jointly for the above-mentioned two treatment lines 3, 3' in a single tower 24 for vacuum degassing. The mixture of purified wastewater from chamber 23 is delivered into the secondary sedimentation tank 1.

The arrow V denotes the direction of externa! recirculation from the secondary sedimentation tank 1 of the sludge collected from the wells 13 collecting the sediment sludge and directed into the chamber 22 at the inflow of wastewater from the collector 21. As shown in fig. 4, the inflow of wastewater into the sludge hopper 11 of the secondary sedimentation tank 1 is realised via conduit 12.

According to fig. 5 and fig. 6, the wastewater treatment plant has a secondary sedimentation tank 1 with a radial shape, with the vertical flow of wastewater, delimited by its mantle 5, outside of which there are distributed elements of two parallel and independently operating lines 3, 3', carrying out the wastewater treatment processes in a continuous flow system, closed by a cylindrical outer mantle 6. Said elements of the lines carrying out wastewater treatment processes may be generally combined arbitrarily, depending on the requirements of the wastewater treatment process.

Typically, in the space delimited by the mantle 5 and the outer mantle 6, there are placed elements such as the dephosphorisation chamber 7, 7\ the denitrification chamber 8, 8' and the nitrification chamber 9, 9'.

It is apparent and known in state of the art that from the nitrification chamber 9, 9' they have a recirculation-return connection with the denitrification chamber 8, 8'.

Each of the two lines carrying out wastewater treatment processes is connected to a shared chamber 23 of additional denitrification and removal of the remains of easily accessible carbon, connected to one tower 24 for vacuum degassing shared by both lines.

It is also apparent that the secondary sedimentation tank 1 is provided with an outflow of the purified wastewater and it is connected to the inflow of wastewater into the dephosphorisation chamber by the externa! recirculation of the sediment sludge . The secondary sedimentation tank 1 is divided by the partition 10 in the form of a vertical wall placed diametrically, into two zones A and B, serving the function of a secondary sedimentation tank for each of the two treatment lines respectively. Each of these zones is limited by conical walls of the sludge hopper 11 and 11', ended from the bottom with independent wells 13 and 13' collecting the sludges sedimenting on the bottom 2 of the sedimentation tank and recirculated in the beginning of the wastewater treatment process.

It has been assumed that the semi-annular recesses 15 and 15' under the conical walls of the sludge hopper 11 and 1 can constitute spaces for conveniently placing on them all or some elements of lines carrying out the wastewater treatment processes, if the spaces between the mantle 5 of the sedimentation tank and the outer mantle 6 are not sufficiently capacious. Adjacent to the mantle 5 of the secondary sedimentation tank 1 there are semi-annular troughs 17, 17' placed on the outer side for the recirculation of denitrification, which can also be realised via conduits with the flow directed in accordance with the arrows X. From the inner side of the mantle 5 of the sedimentation tank said troughs are outflow troughs for purified wastewater.

On the other hand, along the partition 10, on its both sides, there are placed inflow troughs 12, 12' for purified wastewater flowing into the sedimentation tank 1.

The arrows Y denote the directions of the flow of wastewater in the space delimited by the mantle 5 and the outer mantle 6, while the arrows Z denote schematically the outflow of the purified wastewater from the semi-annular interna! troughs 16, 16' of the wall 5, while the inflow of internal recirculation wastewater from the troughs 17, 17' is referred to as X.

Raw wastewater to be purified is delivered to the chamber 22 from the collector 21 ; also, sludges are delivered to it as recirculated materials from zones A and B of the secondary sedimentation tank 1 , which is denoted by arrows V, V. From the chamber 22, a mixture of raw wastewater and recirculating sludges is distributed into the above- mentioned two biological wastewater treatment parallel and independently operating lines 3, 3', which is denoted by arrows Y, Y\

A chamber 23 for the additional removal of nitrates and vacuum degassing of sludges is placed generally opposite, diametrically in relation to the chamber 22, combining and realised jointly for the two above-mentioned treatment lines in a single tower 24 for vacuum degassing. The mixture of purified wastewater from the chamber 23 is delivered into the secondary sedimentation tank, being divided into two streams directed into zones A and B, constituting independently working secondary sedimentation tanks for either of the both treatment lines.

In fig. 6 the arrows V denote the directions of internal recirculation from zones A or B of the secondary sedimentation tank 1 of sludge collected from the welis 13, 13' collecting the sediment sludge and directed into the chamber 22 at the inflow of wastewater, these wells being placed in direct proximity to the partition 10.

As shown in fig. 6, via conduits 12, 12' the inflow of wastewater is realised to both zones A and B of the sedimentation tank 1 respectively.

In accordance with fig. 7 and fig. 8, another embodiment of the wastewater treatment plant is shown with the secondary sedimentation tank 1 , generally similar to the treatment plant shown in fig. 5 and fig. 6, and described below using the same references for its analogical elements and components.

Also in this case, the secondary sedimentation tank 1 is divided by the partition 10 in the form of a vertical wall placed diametrically, into two zones A and B, serving the function of a secondary sedimentation tank for each of the two treatment lines 3, 3' respectively. Each of these zones is limited by conical walls of the sludge hopper 11 and 1 1 ', ended from the bottom with two independent wells 13 and 13' collecting the sludges sedimenting on the bottom 2 of the sedimentation tank 1 and subjected to recirculation in the beginning of the wastewater treatment process. The conical walls of sludge hoppers 11 and 1 1 ' are not the walls of a regular inverted cone, but they are shaped in such a manner that the angles of their inclination, measured along the dashed line of the diameter denoted in fig.7, are different and the angle a measured from the side of the partition 10 is larger than the angle β, measured from the side of the mantle 5 of the sedimentation tank 1.

In the embodiment presented in fig. 7 and fig. 8, the wells 13, 13' for the collection of the sediment sludge is not placed in direct proximity to the partition 10, but they are at a certain distance 14 from the partition 10. Moving the wells 13, 13' collecting the sediment sludge away, for example by 2 metres from the partition 10, with the proper adjustment of the inclination of the walls of sludge hoppers 1 1 and 1 1 ' with a relatively small increase in the diameter of the circle described by the wall 5 results in achieving almost double increase in the area of the sedimentation tank, which is larger than the area of the sedimentation tank with wells 13, 13' placed directly at the partition 10, like in fig. 5 and fig. 6, or like in known solutions without the partition. This results in the possibility to increase the diameter of the secondary sedimentation tank 1 with the same depth of the water layer, e.g. 9 m.

The sizes of the sedimentation tanks were compared while adjusting the angles of inclination of the walls of sludge hoppers 11 and 1 ' and the same depth of 9 m for performing the treatment process. For the sedimentation tank according to fig. 5 and fig. 6, the diameter of the sedimentation tank will amount to 11 m with its area of F = 95 m². The diameter of the sedimentation tank from fig. 1 and fig. 2 assumed to be 11 m increases twice by 2 m from either side of the wall 10, and thus it amounts to:

1 1 m + 2 x 2 m = 15 m,

therefore, the increase in diameter amounts to:

15 m : 11 = 1 , 36 - meaning an increase by 36%. By moving the welis 13 away by 2 m from the partition 10, like in fig. 7 and fig. 8, we will get the diameter of the sedimentation tank increased twice by two metres, meaning:

11 m + 2 x 2 m = 15 m

Therefore, the area of the sedimentation tank will amount to:

F = 177 m²

meaning that it is possible to use sedimentation tanks with the same depth but with an area larger by 177 m² : 95 m = 1.86, meaning by 86%

and generally by that much increases the efficiency of the whole treatment plant, whose two fines can be realised adjacent to the sedimentation tank mantle.

The efficiency of the sedimentation tank, around which there are mounted the elements of the treatment lines, decides about the size of the wastewater treatment plant, and thus about its efficiency. In the solution according to invention for a specified depth the sedimentation tank is larger by as much as 60%, perfectly increasing the efficiency of the wastewater treatment plant, whose two treatment parallel operating lines 3, 3' encompass the sedimentation tank mantle 5 and in the end of the process connect preferably in a shared node of the additional removal of nitrogen and the remains of easily accessible carbon and they are subjected to the vacuum degassing of sludges, and subsequently they are delivered in recirculation into each of the two zones A and B of the sedimentation tank.

The system according to the invention for the additional removal of nitrogen and the remains of easily accessible carbon in combination with the vacuum degassing of sludge allows conducting the process with sludge concentrations of 7-9 kg dry mass/m³ and easy operation with a water layer of 9 m and more, which additionaily decreases the area required for the realisation of the complete solution of the wastewater treatment plant 2÷2.5 times compared to the known solutions that are dispersed in the field.

Besides that, in special cases, for example for a cold climate or for limiting the environmental impact, which requires a covering or heating, particular saving possibilities are achieved. Comparative embodiment

An embodiment for the solution according to fig. 7 and fig. 8:

for 11700 inhabitants

flow Q = 1400 m³/day

with the following contaminations in the inflow of wastewater into the treatment plant:

COD = 123 kg/ day O2

Nitrogen N = 140 kg/ day

Phosphor P = 26 kg/ day

Suspension = 820 kg/ day.

It is required to achieve a very high degree of wastewater treatment at the outflow:

N = 10 g/m³

T = 12°C, for a process in wastewater temperature of T = 12°C

P = 0.5 g/m³

BOD = 5÷10

Suspension - 10 g/m³

Process parameters during the use of the technology of the additional removal of nitrates in combination with vacuum degassing of sludge MLVD-N:

The used concentration Z of the activated sludge in process chambers:

Z = 7.5 kg dry mass /m³

The load of the secondary sedimentation tank Oos with dry mass of sludge calculated net without recirculation:

Oos = 60 kg dry mass /m² / day.

Therefore, the required size F of this sedimentation tank will amount to:

F = (Q x Z ) : Oos

F = (1400 x 7.5) : 60 = 175 m².

A sedimentation tank with a diameter of 15 m has been assumed.

To fulfil the requirement of good wastewater treatment it has been assumed to use the process with a sludge load of:

0.08 kg/kg.

Therefore, the required amount of sludge G in the process:

G = 702 : 0.08 = 8775 kg dry mass. With a sludge concentration of Z = 7.5 kg/m³ the required cubage V of activated sludge chambers will amount to:

V = 8775 : 7.5 = 1170 m³.

With the depth of the chambers of H=9.0 m the area F of these chambers will amount to:

F - 1170 : 9 = 130 m².

Therefore, the total area of the sedimentation tanks and chambers F' will amount to:

F' = 130 + 177 = 307 m².

A diameter encompassing the whole area of the treatment process delimited by the outer wall will amount to 19.8 m. Assuming 21 m, it will be enough to satisfy the needs of dephosphorisation chambers and additional nitrogen removal chambers connected to the tower for vacuum treatment.

When using the solution shown in fig. 3 and fig. 4, the treatment plant could only take a part of this amount from the previous comparative embodiment of the sizes of sedimentation tanks of approximately

(95 : 177) χ 1400 m³ = 752 m³/ day,

and the diameter of the external wall would amount to approximately 16 m.

Therefore, for this amount of flow, it would be necessary to use almost two treatment plants from fig. 3.

As shown in fig. 9 and fig. 10, the wastewater treatment plant has a secondary sedimentation tank 1 with a radial shape, delimited by its mantle 5, outside of which there are distributed selected elements of two parallel and independently operating lines 3, 3', carrying out wastewater treatment processes in a continuous flow system, enclosed by an external housing 6 with the shape of a roller. The selected elements of the lines carrying out wastewater treatment processes may be generally combined arbitrarily, depending on the requirements of the wastewater treatment process.

The space delimited by the mantle 5 and housing 6 is intended for the placement of dephosphorisation chambers 7 and 7' and nitrification chambers 9, 9', belonging to both treatment lines 3, 3'. On the other hand, the anaerobic stages of denitrification and/or dephosphorisation in both treatment lines 3, 3' are carried out in denitrification chambers 8, 8' under the sedimentation tank bottom in the space 25 for anaerobic processing, divided by the separating wall 26, for example, into denitrification chambers 8, 8^!. From the nitrification chambers 9, 9' there is a recirculation-return connection with the denitrification chambers 8, 8' via inflows referred to as P.

The inflow from dephosphorisation chambers 7, 7' into each denitrification chamber 8, 8' of the two treatment lines 3, 3' occurs via the space created between the wall 5 and the wali 5\ moved away towards the wali 6, delimiting a part of the space to the height of walls 5 and 6. This space constitutes a part of the denitrification chamber 8, 8' placed under the bottom of the sedimentation tank. Inside it there are placed circulation movement devices of each of the two denitrification chambers 8, 8', where each of them constitutes a line with the associated lines 3, 3'. The inflow from the dephosphorisation chambers is denoted by arrows P, P'; further outflow from the denitrification chambers to the nitrification chambers is denoted by arrows Y, while the inner recirculation is denoted by the arrow X.

Circulation of the denitrification area is shown by arrows R.

Each of the two lines 3, 3' carrying out wastewater treatment processes is provided with a chamber 23 for additional denitrification and removal of the remains of easily accessible carbon, connected to one tower 24 for vacuum degassing shared by both lines, similar to the treatment plants described above.

It is apparent that the secondary sedimentation tank 1 is provided with an outflow of the purified wastewater and it is connected to the inflow of wastewater into the dephosphorisation chamber by the external recirculation of the sediment sludge from the well 13 into the shared 7 or bipartite space 7, T for each 3, 3'.

The secondary sedimentation tank 1 has a bottom 2 with a slope denoted by arrows towards its geometrical centre, provided in its geometrical centre with a well 13 collecting the sediment sludge.

The arrows M' in fig. 10 denote schematically the inflows of wastewater into the secondary sedimentation tank 1 , and in fig. 9 the arrows P denote schematically the denitrifying recirculation.

The wastewater subjected to treatment is delivered by the collector 21 into the dephosphorisation chambers 7, 7' or a shared chamber separating the flow into two treatment parallel operating lines .

The separating wall 26 extends generally diametrically in the space 25 for anaerobic processing, dividing this space into two denitrification chambers 8, 8', one for each of the lines 3, 3', and also serves the function of a wall supporting and holding the bottom 2 of the secondary sedimentation tank 1 , at the same time constituting the ceiling of the chambers 8, 8' for denitrification, meaning anaerobic processing.

Furthermore, each of the denitrification chambers 8, 8' is divided by labyrinth walls 27, delimiting the flows of wastewater and sludges in this chamber, in accordance with the arrows R. independently of the function of organising the flows of wastewater and sludges subjected to denitrification, the labyrinth walls 27 additionally also serve the function of support walls for the bottom 2 of the secondary sedimentation tank 1 , which is subjected to considerable loads.

The embodiment presented in fig. 9 and fig. 10.

Wastewater flow rate Q = 20000 m³/ day.

The concentration of wastewater after sedimentation tanks:

BOD = 250 g/m³

Contamination load L:

L = 20000 0.25 = 50000 kg/ day O2.

Equivalent number of inhabitants RIM = 83300.

The assumed necessity to obtain good results of treatment for sludge load O:

O = 0.08 kg load/kg sludge.

The concentration of sludge in a process with the additional removal of nitrogen in combination with the vacuum degassing of sludge:

Z = 7.5 kg/m³

- depth of aeration chambers H:

H = 9.0 m

- the net load of the secondary sedimentation tank without recirculation:

Oos. = 60 kg dry mass /m²/ day.

The area of the sedimentation tank will amount to:

F = (Q x Z) : Oos = (2000 ^χ 7.5) : 60 = 2500 m²

diameter D = 56 m.

The amount of sludge necessary for the treatment process:

G = L : O = 5000 : 0.08 = 62500 kg

The required cubage of chambers V with a sludge concentration of 7.5 kg/m³

V = 62500 : 7.5 = 8333 m³

with the depth of the activated sludge chambers of H = 9.0 m

the areas of the activated sludge chambers F will amount to: F = 8333 : 9.0 m = 926 m².

Reducing this value by the denitrification space extending under the bottom of the sedimentation tank amounting to 30% and adding approximately 15% for the space of dephosphorisation and the additional removal of nitrogen with the vacuum degassing tower, this area will amount to:

F = 926 m² x 0.85 = 787 m².

The total area of the whole compact treatment plant F' will amount to:

F' = 2500 m² + 787 m² = 3287 m².

Therefore, the external diameter of the treatment plant wall will amount to:

D = 65 m.

Therefore, the zone of the biological line will have a width of:

S = 4.5 m.

The compact biological wastewater treatment plant constructed in such a manner is capable of serving approximately 83000 inhabitants.

In the case of using additional preliminary sedimentation tanks, the number of served inhabitants RIM will increase to approximately:

RiM = 120000 people.

It is apparent that connecting such modules in parallel will create a treatment plant of any size.

Such a completed block also includes all ancillary facilities, like pumping stations for recirculated materials, conduits connecting flow processes, etc.

Treatment plants for the needs of this number of inhabitants can also be organised using two smaller facilities compacted in such way. The diameter of each such facility would amount to 46 m.

Smaller wastewater treatment plants can also be organised in a similar way.

List of references

1 secondary sedimentation tank

2 sedimentation tank bottom

3 and 3' treatment lines

4 partitions dividing the processes of treatment lines in the case of preliminary sedimentation tanks preceding a biological wastewater treatment plant

5 sedimentation tank mantle

6 external mantle 7 and 7' dephosphorisation chambers

8 denitrification chamber

9 nitrification chamber

0 sedimentation tank partition

11 sludge hopper, sludge piling wails

12 conduit, trough for inflow into the sedimentation tank

13 and 13' wells

14 distance of the we!ls from the partition

15 and 5' recesses

16 purified wastewater troughs

17 and 17' internal recirculation troughs

18 the outflow of purified wastewater, arrow Z

19 internal recirculation

20

21 wastewater inflow collector

22 inflow chamber

23 additional denitrification chamber

24 vacuum degassing tower

25 anaerobic processing space

26 separating wall

for fig. 9,10

M inflows into the secondary sedimentation tank P inflow into the denitrification chamber

R directions of circulation of liquids

BOD biological oxygen demand - L

COD chemical oxygen demand

Claims

29871/17 Claims

1. A biological wastewater treatment plant operating in a continuous flow system in two parallel and independent lines, in which wastewater is subjected to the consecutive stages of removing various forms of contaminations contained therein, and each of the lines is equipped for selected optionally from elements such as a dephosphorisation chamber, a denitrification chamber and a nitrification chamber, from which there is a recirculation-return connection with a denitrification chamber, as well as a chamber for additional denitrification and removal of the remains of easily accessible carbon, connected to a vacuum degassing tower, as well as a secondary sedimentation tank with the outflow of the purified wastewater, connected to an inflow of sludge to the dephosphorisation chamber by external recirculation of the sediment sludge, having a form of a tank with sidewalis convergent towards each other and towards the bottom, accumulating sediment sludge being collected on the bottom in a well, characterised in that the elements of each of the two wastewater treatment parallel and independently operating lines (3, 3J_.) are positioned outside the secondary sedimentation tank (1) and in a space adjacent to the mantle (5) of the secondary sedimentation tank (1), and each of these two lines (3, 3_ ) is delivered to one common node, comprising a tower (24) for vacuum degassing and an additional denitrification chamber (23).

2. The wastewater treatment plant according to claim 1 , characterised in that the tank of the secondary sedimentation tank (1) is divided by a partition (10) into two zones (A, B) of secondary sludge sedimentation, each zone (A, B) having an independent well (13, 13') collecting the sludges sedimenting on the bottom (2) of the secondary sedimentation tank (1) and the sludges are subjected to recirculation to the beginning of the wastewater treatment process.

3. The wastewater treatment plant according to claim 2, characterised in that a partition (10) has a form of a vertical wall.

4. The wastewater treatment plant according to claim 2, characterised in that the two zones (A, B) of secondary sludge sedimentation are equal.

5. The wastewater treatment plant according to claim 2, characterised in that the wells (13, 13') collecting the sediment sludge is placed in a direct vicinity of the partition (10), preferably close to a vertical axis of symmetry of the secondary sedimentation tank (1).

6. The wastewater treatment plant according to claim 5, characterised in that the wells (1_3, 13') collecting the sediment sludge are placed each at a distance (14) on each of the two sides of the partition (10).

7. The wastewater treatment plant according to claim 5 or 6, characterised in that each of the wells (13, 13') collecting the sludges sedimenting on the bottom (2) of the sedimentation tank constitutes a bottom end of conically shaped zones (A, B).

8. The wastewater treatment plant according to claim 1 , characterised in that in the perimeter part of the secondary sedimentation tank (1), generally in the plane of the partition (10), there is placed a wastewater inflow collector (21).

9. The wastewater treatment plant according to claim 8, characterised in that the wastewater inflow collector (21) is shared and it delivers wastewater indirectly via the inflow chamber (22) or directly into the dephosphorisation chamber (7), from which a division into two independent treatment parallel operating lines (3, 3_1) occurs.

10. The wastewater treatment plant according to claim 8, characterised in that the wastewater inflow collector (21) delivers wastewater into the space (7) divided into (Z, Zl), each of which is assigned to the corresponding treatment line (3 and 31).

1 . The wastewater treatment plant according to claim 1 , characterised in that the selected elements of the two biological wastewater treatment parallel and independently operating lines (3, 3_1) are distributed inside the secondary sedimentation tank (1), in the spaces (15, 15') delimited outside the conical wails (H, 1 Γ), delimiting the zones of secondary sludge sedimentation.

12. The wastewater treatment plant according to claim 1 , characterised in that under the secondary sedimentation tank (1) and preferably under the bottom (2) of the secondary sedimentation tank (1) there is a space (25) for anaerobic processing, for the stages of denitrification and/or dephosphorisation.

13. The wastewater treatment plant according to claim 12, characterised in that the space (25) for anaerobic processing is divided by a separating wall (26) into denitrification chambers (8, 81) for the individual treatment lines.

14. The wastewater treatment plant according to claim 13, characterised in that the separating wall (26) extends in the space (25) for anaerobic processing diametrically, at the same time serving the function of an element supporting and holding the bottom (2) of the secondary sedimentation tank (1), at the same time constituting a ceiling of the space (25) for anaerobic processing.

15. The wastewater treatment plant according to claim 13, characterised in that each of the denitrification chambers (8, 8_ ) is divided by labyrinth walls (27) delimiting the flows of wastewater and sludges in this chamber, at the same time additionally serving the function of supporting walls of the bottom (2) of the secondary sedimentation tank (1).