WO2022146265A1

WO2022146265A1 - Single unit vertical aerobic / anaerobic biological wastewater treatment plant without pre-setllement unit

Info

Publication number: WO2022146265A1
Application number: PCT/TR2020/051499
Authority: WO
Inventors: Olcayto KESKINKAN; Cagatayhan Bekir ERSU
Original assignee: Cukurova Universitesi Rektorlugu
Priority date: 2020-12-28
Filing date: 2020-12-31
Publication date: 2022-07-07
Also published as: TR202021985A2

Abstract

The invention relates to the design of a double layer vertical aerobic / anaerobic downstream biological treatment plant (with cell dividing structure) without primary settling, which is not encountered in previous studies, which includes a new approach in biological treatment of wastewater.

Description

SINGLE UNIT VERTICAL AEROBIC / ANAEROBIC BIOLOGICAL WASTEWATER TREATMENT PLANT WITHOUT PRE-SETLLEMENT UNIT

TECHNICAL AREA

The invention relates to the design of a double layer vertical aerobic I anaerobic (with dividing structure) downstream biological treatment plant without primary settling, which is not encountered in previous studies and includes a new approach in biological treatment of wastewater.

PREVIOUS TECHNIQUE

Activated sludge is the most common biological process in the world. It is used in municipal and industrial wastewater treatment with applications ranging from small package facilities for detached houses to large facilities serving metropolitan areas. The activated sludge process was first announced by Ardern and Lockett (Ardern and Lockett, 1914) on April 3, 1914 to the Chemical Industry Association in the Grand Hotel, Manchester, England, and it originated from research on sewage and purification. The activated sludge process built on these experiments was carried out in the United Kingdom in 1913 by two engineers, Edward Ardern and W.T., who conducted research for the Manchester Corporation Rivers Department at Davyhulme Sewer Works. It was perfected and patented by Lockett (Ardern and Lockett, 1914). They experimented with treating wastewater in a fill-discharge reactor such as a sequencing batch reactor that produces high quality effluent. They believed that the sludge was activated during the process, hence the name activated sludge. They understood that it was microorganisms that mediated the conversion of carbonaceous pollutants into carbon dioxide, water, and energy for regrowth. After that, activated sludge processes has begun to become common (Figure 1 ).

The activated sludge process has 5 basic functions:

1 ) Suspension of microorganisms flocculated by mixing and ventilation

2) Extra microorganism and gas production as a result of oxidation of dissolved and particulate organic matter with oxygen or nitrate I nitrite

3) Liquid-solid separation to obtain purified water with low total suspended solids 4) Returning some of the sludge in the sludge-liquid separation part in the effluent to the aeration tank where the treatment is performed

5) Discarding excess sludge to achieve the desired sludge age

The development of the activated sludge process continued in 1914 with the aim of removing BOD and total TSS for wastewater treatment, removing nitrogen in the 1960s, and removing P in the 1970s. During this time and during the 1980s, as process development continued, efforts were made to overcome settling and foaming problems. In the 1980s, 90s and early 21st century, process improvement was attempted to reduce activated sludge reactor volume and save energy (Jenkins & Wanner, 2014).

The activated sludge process was quickly adopted and implemented. Even before 1914, work was underway to treat the 303 m3 I day of wastewater in Salford (England) (Melling 1914; Jenkins D., Wanner J., (2014). In the United States, advanced tests were being conducted in Illinois (Bartow and Mohlman 1915; Jenkins D., Wanner J., 2014). This study was followed by a study with a continuous flow system including screen, grit removal, separate aeration and settling tank, sludge drying to treat 750 m3 I day wastewater (Barlow, 1917; Jenkins and Wanner, 2014). Later, continuous flow piston flow aerated systems with a flow rate of 7,570 m3 I day and then a flow of 170,325 m3 I day in Milwaukee were tried. A series of 8 tanks and an circular settling tank were tested in this system (Metcalf and Eddy, 1922; Jenkins), and Wanner, 2014). In 1927, very large treatment facilities were established in the USA (Jenkins & Wanner, 2014).

Other countries started to establish activated sludge process as well. Seven facilities were built in 1924 in Ontario, Canada (Wolman, 1924; Jenkins & Wanner, 2014). The first German full-scale AC treatment facility was established in Esen in 1925 and this facility made the first use of anaerobic digesting gas as fuel (Seeger, 1999; Jenkins and Wanner, 2014). Brush aerators (aerators) were developed by Kessener in Apeldoorn, the Netherlands, were used in 1927 (Cooper, 2001 ). In 1936, Ney started an OP plant with a capacity of 681 ,300 m3/day on Wards Island, New York City. In 1938, there were 203 activated sludge (AS) acilities in the USA and these facilities were spread over the continent (Allema and Prakasam, 1983; Cooper, 2001 ). As the process was understood better and region-specific needs emerged, new designs were developed to restank to varying treatment needs. As it became clear over time how to reduce the need for oxygen, Kessler et al. (1936) developed the first "Tapered Ventilation" system. “Step Aeration” was used by Gould (1942) for the New York City AS facility (Jenkins & Wanner, 2014).

Preventing eutrophication has become the next goal of wastewater treatment when secondary treatment and reduction of carbonaceous contaminants are implemented in most treatment plants. Depending on the receiving waters, many treatment facilities need to remove nitrogen, phosphorus, or both. Studies conducted by Downing (Downing et al., 1964: Jenkins D., Wanner J., 2014) are now included in the design methods of biological nitrification. In 1962, Ludzack and Ettinger advanced, continued, and launched the use of an anoxic zone to achieve biological denitrification in the activated sludge process, an application that is now widely implemented (Lutdzack & Ettinger, 1962; Jenkins D., Wanner J., 2014). Biological removal of nitrogen and phosphorus in a single sludge system was developed and patented by James Barnard (Barnard, 1973, 1974, 1975) (Figure 2).

Basic Operations in Treatment of Domestic Wastewater

The following basic processes are used in the treatment of domestic wastewater:

First Stage (Pre) Treatment

Wastewater first stage treatment processes should be designed to meet the following conditions (TS EN 12255-3, DIN EN 12255-3):

• Providing appropriate conditions for effective and efficient operation of wastewater treatment units,

• Shortening the hydraulic waiting time needed in the facility,

• Ensuring efficient operation of sludge treatment units thanks to fine screen and sieve systems, separating inert materials entering the facility with sand holders,

• Providing the necessary conditions for the safe operation of treatment processes,

• Ensuring the protection of equipment and equipment.

• The first stage treatment units in urban wastewater treatment plants are summarized below. Grids and Screens

With the establishment of grid and screen systems, solid and coarse substances are removed from wastewater. Coarse screens must be installed before pumping stations. Fine screens are installed to remove floating materials that remain in the wastewater after the coarse screens and may damage the mechanical equipment in the following units and thus reduce the clogging in the sludge treatment units (Koyuncu, 2013).

Screen Types

Screens are divided into two as coarse and fine screens based on opening width. Coarse screens are placed at the entrance of the pumping stations to protect pumps against effects such as wear of impellers, clogging, etc. Bar spacing of coarse screens can be 30 ~ 50mm. Collector flow elevations at the entrance of the wastewater treatment plant may be very deep (5.0 - 10.0 m). Therefore, coarse screens installed at the entrance of the plant can also be placed well below the ground surface. Since the length will be long in such deep screens, one revolution of the rake, that is, it can take 2 to 3 minutes from the host place above the water level to return to the first position above the water level, and mean speed is 0.15 - 0.20 m I sec. It is possible to clean the coarse screens manually or automatically. Fine screens are used to reduce the load of structures such as sand traps and primary settling tanks. Bar spacing for fine screens to be used in wastewater can be taken as 10 ~ 30 mm. Fine screens are generally made with mechanical cleaning and rake scraping speed can be 0.10-0.15 m I sec. One revolution of the rake (working cycle) varies between 2 and 5 minutes depending on the size of the screen. Grids are classified as follows in terms of working principle:

Fixed bar screens: These are generally equipped with mechanical equipment. Rotary screens: These are usually cleaned with pressurized water.

Grinders: These do not need to be cleaned as they grind the waste they hold and mix them back into the water.

Pumping Stations

Wastewater pumping stations (pumping stations) raise the wastewater coming from within the sewage system to the ground surface and transfer wastewater from one place to another. Grit and Oil/Grease Removal

Grit/Oil/Grease removal is an important component to reduce the problems caused by grit, sand, and oil/grease in wastewater. Small inorganic particles such as sand cannot be decomposed biologically and damages mechanical equipments and pumps. Sand accumulates in channels, settling tanks, sludge digestion and sludge dewatering units creating serious operational problems. Oil, on the other hand, creates a problem especially in settling and is stripped from the final settling surface (MWA, 1998; Koyuncu, 2013). In grit removal systems, the flow velocity is reduced to precipitate large particles and the sand is then removed from the tank floor. Oil and grease is stripped from the tank surface. The combined system contains a significant amount of grit and sand entering the system from sewer networks, road and pedestrian sidewalks and flood beds. Separated sewer systems contain sand especially from coastal or beach areas. Because of its harmful effects, the grease must be removed before it starts to dissolve or disperse. Where there are domestic and urban wastewater containing discharges from hotels, restaurants and food processing facilities, treatment facilities should have a grease and oil removal stage in the design. As an alternative to grease removal, it may be possible to combine grit and grease I oil retention in a single unit or as a separation stage in the first settling tank. Grease and oil removed from wastewater should be disposed of in accordance with the health and safety conditions specified in DIN EN 12255. The design of the grease separator should facilitate the safe and effective removal of separable solids, grease and oil (Koyuncu, 2013).

Flow Measurement

In wastewater treatment plants, routine measurement of wastewater flow is essential for the design and operational control of the facility. The benefits of knowing average and daily flow rate changes can be summarized as follows:

• Determining the daily amount of chemicals to be added to the system

• Determining the amount of air to be supplied to the system

• Determination of sludge recycling rate

• Establishing existing flow rate records when it comes to enlarging the facility • Significant flow rate increases determined in daily dry weather conditions; obtaining information about industrial wastewater discharge and population growth into the seepage or sewage system

• Estimating the rainwater contribution based on the significant flow rate increase in rainy weather conditions

Flow Equalization

Equalization tanks are used to compensate for fluctuation in flow and pollution load and to reduce the hydraulic load in the initial settling tank. In cases where there are long aerated activated sludge systems with a holding time of more than 18 hours and settling tanks sized according to peak flow, flow equalization is not used. In the equalization tank, mixing is applied to stabilize the concentration and prevent precipitation. Partial oxidation of oxidizable substances and BOD also takes place with mixing and aeration. Mixing methods in balancing tanks are as follows;

• Distribution and screening of the inlet stream,

• Mixing with turbine mixers,

• Aeration with diffusers,

• Aeration with mechanical aerators,

Flow equalization may be required in flow measurements. Flows exceeding the design capacity of later stages should be directed into the flow balancing tank. This should be after screening and grit removal.

Primary Settling

Primary settling is the separation of solids that can settle down. With the removal of solids from raw wastewater, certain amounts of suspended solids and BODs are also removed. With the removal of the foam in the raw wastewater, the formation of foam in the aeration and final precipitation tanks is reduced. Another important task of primary settling tanks is balancing the changes in concentration and flow rate of raw wastewater. These tanks are installed at wastewater treatment plants with large capacities (> 3800 m³ I day). In smaller plants, there is no need for a primary settling unit in cases where the capacity of the second stage treatment units is sufficient and there are no operational problems caused by floating residues such as foam and oil. Primary settling tanks should be built before second stage treatment systems such as trickling filters, rotary biodisks, and biofilters. In a well-designed and properly operated primary settling unit, 30-35% BODs, 50-60% suspended solids removal is achieved in typical domestic wastewater. In urban wastewater, where industrial wastewater contribution reaches significant rates, these rates change due to the difference in the amount of dissolved BODs in the wastewater. When chemicals are added to the primary settling tank, treatment efficiency increases significantly. BODs and SS removal may fall below typical values due to extreme conditions such as hydraulic short circuits in the settling tank, excessive oscillations in the wastewater flow, very high or low wastewater temperatures and high recycle rates.

The wastewater flow that will enter a treatment facility with a well-planned first stage treatment should be balanced and the subsequent treatment units should be designed in a way that will not be damaged by flow fluctuations (TS EN 12255-3; Koyuncu, 2013).

SECOND STAGE TREATMENT (BIOLOGICAL TREATMENT)

In this section, activated sludge systems, trickling filters, biodisk systems, and lagoons are discussed.

Activated Sludge Systems

General Introduction of Biological Treatment (Second Stage Treatment)

It is a treatment method in which microorganisms suspended or attached to the surface are used to bring the wastewater to the desired quality. After the wastewater is subjected to biological treatment, microorganisms (biomass) that perform the purification function must be separated from the treated water by various methods (final precipitation, membrane filtration, etc.). The performance of the system depends on the biodegradability of wastewater, the selected process, biological and chemical reactions in activated sludge tanks, and the separation efficiency of biomass from treated water. An activated sludge system can be applied for all wastewater suitable for biological treatment (Koyuncu, 2013).

General requirements in an activated sludge system are given below.

• The design to be carried out must comply with the discharge standards and regional needs.

• Dead zones and accumulation in tanks and hoppers should be prevented. • Ventilation and I or mixing equipment should be checked.

• Surface area, volume and depth of final settling tanks should be checked.

• The sludge scraping and collection system in the final settling tanks should be selected appropriately.

• Sludge return and excess sludge discharge equipment should be selected.

• The sludge formed should be treated and moved to the end point.

• Hydraulic head loss should be minimum.

• The shape of the flow in the reactor depends on the process chosen. In case of feeding from different points (gradual ventilation, etc.), equipment (such as valves, caps) that allows changes to the original flow pattern should be provided.

• Measuring, automation and control should be implemented to allow the facility to adapt to variable conditions and to keep the adaptation process at a minimum.

In activated sludge process design, it is aimed to determine the outlet concentrations of the aeration tank volume, sludge formation amount, oxygen demand and important parameters. For the correct design of an activated sludge process, revealing the wastewater character is the most important step. Biological nutrient (N, P) removal of wastewater characteristics is critical in performance evaluation of processes. Wastewater characterization is similarly taken into account in the performance evaluation and optimization of existing facilities and in determining useful treatment capacity (Metcalf & Eddy, 2003).

Final Settling Tanks

Final settling tanks should be designed to provide sufficient surface area and depth for the settling of activated sludge flocs. In sequencing batch reactor and membrane bioreactor (MBR) design, there is no need to make a final settling tank.

General Principles

• A smooth and symmetrical distribution of the flow rate should be provided in the entrance area of the facility.

• It should be ensured that the water is symmetrically and slowly drawn in the outlet structure, the materials accumulated on the surface are easily collected and the sludge transport to the weirs should be prevented. • Sludge collection and removal should be planned according to the type and size of the final settling tanks.

• In places where sludge reservoirs are constructed, the angle (angle of inclination) of the reservoir sides with the horizontal should not be less than 60 degrees for pyramid-shaped reservoirs and 50 degrees for conical-shaped reservoirs.

• For small units, sludge should be able to be collected by gravity on surfaces with fairly high slopes (eg 50 °-60 °) and as smooth as possible.

• In plants with biological nitrogen removal, excessive waiting of the sludge in the final settling tank should be prevented.

Final settling tanks can be designed to discharge mud from the center or from the edge, depending on the geometry of the tank. For activated sludge systems with wastewater treatment capacity more than 400 m³ 1 day, more than one final settling tank should be planned.

When one of the tanks is disabled, other tanks must be capable of exceeding the maximum hourly flow rate. In systems that do not have more than one settling tank, measures to ensure continuous treatment must be specified. If the inner diameter of the final settling tank exceeds 50 m, measures should be taken to minimize the effect of the wind. Water depth at the edge should be at least 3.7 m for suspended systems. For systems that grow on the surface, the edge water depth will be taken at least 3.0 m. Lower side water depth may be preferred in (package) treatment systems with a treatment capacity of less than 100 m³ 1 day. As for solid matter load, maximum hourly flow rate values for wastewater flow (Q) and the sludge return cycle (QRAS) should be taken into account. The final settling tank air margin should be at least 0.3 m. The side wall top level must be at least 15 cm above the ground level. If the sludge is to be collected from the last settling tank with the scraper system, the bottom slope towards the sludge reservoir should be planned as 1 / 15 (Vertical - Horizontal).

Sludge Stabilization (Sludge Digestion)

Stabilization of sludge is the process of bringing sludge to a stable structure that can be disposed of without causing any harm to the environment and creating a bad odor. Treatment sludges are stabilized to remove pathogens, prevent unpleasant odors, reduce, inhibit or stop potential degradation. The success of achieving these is related to the effect of the stabilization process on the volatile or organic part of the sludge. When designing the stabilization process, the compatibility of the stabilization process with other treatment units is important. For sludge stabilization;

• Lime stabilization

• Thermal treatment

• Airless rotting

• Air digestion

• Composting methods are used (Koyuncu, 2013).

BRIEF DESCRIPTION OF THE INVENTION

Single unit biological wastewater treatment plant without pre-drifting, vertical aerobic I anaerobic sludge, which is the subject of our invention, is a treatment plant that has not been encountered in previous studies. Although various forms of aerobic I anaerobic biological treatment systems have been encountered, no facility has been found that has the advantages of the vertical (vertical) array in this study. Previous or conventional Aerobic-Anaerobic systems require additional equipment as detailed below.

LIST OF FIGURES

Figure 1. Classical (conventional) activated sludge system in the known technique without sludge digestion

Figure 2. Bardenpho process flow chart for nitrogen and phosphorus removal in conventional systems of the known technique

Figure 3. General view of the treatment plant subject to the invention

Giving the names of the part numbers indicated in the figures with the reference number

1. Preliminary Settlement Tank

2. Activated Sludge Aeration Tank

3. Air Blower

4. Final Settlement Tank

5. Airless Tank

6. Anoxic 1 Tank

7. Aeration Tank 8. Anoxic 2 Tank

9. Air Tank

10. Vertical Treatment Boiler

10.1 . Aerobic Section

10.2. Anaerobic I Anoxic Section

DETAILED DESCRIPTION OF THE INVENTION

Our invention relates to a vertical purification vessel (10) comprising at least one aerobic section (10.01 ) and an anaerobic I anoxic section (10.02). Our invention aims to solve the technical problems experienced in conventional horizontal treatment systems in the known technique. First of all, the basic problems in conventional biological treatment plants are

1 ) High initial investment costs due to the need for excess space,

2) The large number of units and the running of the process increase the operating cost of the equipment, materials and methods used to provide flow between units.

The solution is to make new designs that will save space in order to reduce the initial investment cost, reduce the operating costs by reducing the number of units to be used, materials, materials and methods.

For this purpose, we have solved the basic problems we have identified in conventional systems (CS) with "Single Unit Biological Wastewater Treatment Plant with Vertical Aerobic I Anaerobic Sludge Digestion without Primary Settling" (VAASDWPS). In order to be well understood, it is explained in conventional systems which units are located on the way of wastewater and how the system works, and how the invention works comparatively.

The general flow chart of conventional systems was given in Figure 1 . Basic units that are usually in conventional systems as described in the Previous Technique section are;

• Grids and Screens

• Pump Stations

• Sand and Oil Retainers

• Balancing

• Pre-settled

• Active Sludge aeration tank (2) • Nitrification tank (No need for C and N removal together)

• Denitrification tank

• Final Settling Tank (4)

• Sludge Stabilization (Sludge Digestion)

Basic units included in the invention (VAASDWPS) are;

• Grids and Screens

• Pump Stations (less number of pumps)

• Sand and Oil Retainers

• Balancing

• Vertical Anaerobic sludge digestion base Activated Sludge aeration tank

• Final Settling Tank (4)

The invention (VAASDWPS) is based on removing suspended solids (SS), carbon (C), and nutrients in the inlet wastewater. When Figures 1 and 2 are examined, the preliminary and intermediate settling tanks as the most basic units of conventional systems take up a significant amount of space. There is no need for primary settling tanks (1 ) in the facility subject to our invention. In the facility subject to our invention, wastewater first passes through a screen followed by grit and oil/grease removal unit, and since there is no primary settling, it comes directly to the treatment plant. Here, in conventional systems, there are factors that increase investment and operating costs such as primary settling tank (1 ), nitrification tank, denitrification tank, sludge digesters and intermediate settling tanks, pumping systems and using external C resources. In the treatment plant subject to our invention, primary settling, nitrification, denitrification, and sludge digestion take place within the same structure and the piping, pumping, space requirement and energy requirement are considerably reduced compared to conventional systems. In conventional systems, wastewater first passes through screens and sieves, and then comes to the sand and oil holding units. In these units, the retentim time of wastewater is short, and easily settled sand/grit particles and oil masses suitable for swimming are removed. In the treatment facility of our invention, there are screens and grid/oil traps. In conventional systems, after the wastewater passes through equalization, it comes to the primary settling tank (1 ). Here, the particles in the form of particles and precipitate for longer periods pass through tanks of various volumes depending on the flow rate of the wastewater in the tanks, generally circular in shape, with a holding time of about 1 to 3 hours. The problem with the settling tank in conventional systems is that the settling tank has a significant operating cost due to the extra space occupation, equipment requirement (scraper traveling bridge, floor scraper, sludge discharge pump) and energy requirement.

In our invention, a double-layered vertical treatment tank (10) is constructed with at least one aerobic section (10.1) on the upper layer and at least one anaerobic I anoxic section (10.2) on the lower layer. In this way, the solids that can settle in the plant break down in the anaerobic substrate. Since the upper layer, which is the aerobic section (10.1 ) where the wastewater enters, is ventilated, it works with the principle of aerobic activated sludge (AS) system. Since the hydraulic retention time in this unit is too much compared to a sedimentation pool, the solids that can settle over time in a fully mixed environment, whose sedimentation rate is higher than the active sludge, will eventually come from the openings (orifice) at the edges of the upper layer, which is sloping downward from the center to the edge, to anaerobic anaerobic I anoxic section (10.2). Solids that can settle in the lower layer, which is the anaerobic I anoxic section (10.2) with a longer holding time and in an airless environment, undergo anaerobic degradation in the lower layer together with the activated sludge (AC) from the upper layer, which is the aerobic section (10.1 ). Therefore, there is no primary settling tank (1 ) in our invention. Since there is no primary settling tank (1), there is no need for sludge scraper, additional pumping and piping. The absence of a primary settling tank (1 ) ensures that the total area of the treatment plant to be established is lower and the initial investment cost is reduced.

In the system subject to our invention, the aerobic section (10.1) does not have a ventilation diffuser, it must be mixed on the surface. Therefore, it does not include air blowers (3), which are seen in diffuser systems and consume a lot of energy. Therefore, issues such as ventilation pipes, diffusers, head losses, excessive energy requirement in the main unit are not included in the system subject to our invention. This provides ease of operation, energy savings and a reduction in upfront investment cost, and these problems are solved.

Conventional systems can remove nitrogen and phosphorus at certain rates. However, more advanced nitrogen and phosphorus removal is required today to protect the receiving environment. For this reason, required nutrient (N and P) removal efficiencies can be obtained by adding additional anaerobic and / or anoxic units for conventional systems. Among the heterotrophic bacteria removing C in the aeration tank, there should be a certain amount of autotrophic nitrification and in order to provide this amount, the inlet water BODs I TKN ratio should be around 5 in the same tank (C removal and nitrification tank). If nitrification is to be carried out in a separate tank, the BODs I TKN ratio should be around 3 at the inlet of the nitrification tank following the C removal tank.

The problem is that their applications in conventional systems require additional tanks, pumping equipment, piping and space when the above-mentioned processes are desired. In the system subject to our invention, P removal by C and N oxidation occurs in the aerobic section (10.1) in the upper layer, and N denitrification in the lower layer, which is the anaerobic I anoxic section (10.2). Therefore, it does not require additional tanks, pumping equipment, piping and extra space. In the vertical plant subject to our invention, there is no need for an additional sludge digester as the excess sludge passing to the lower layer, which is the anaerobic I anoxic section (10.2), will decompose here. The produced gas (CH4) obtained during sludge digestion will be utilized. Thus, an extra tank is eliminated and additional energy is provided.

In conventional systems, the wastewater passing through the aeration tank and nitrification carries a low C (BODs) but still contains nitrogen (NO3). The problem is that an anaerobic tank (5) or anoxic tanks (6,8) are required after aeration and nitrification to achieve this. Denitrification is required to remove nitrogen from the largely removed wastewater from organic carbon containing plenty of NO3, and for this it is necessary to add a denitrification tank (7). In the system subject to our invention, when the nitrified water, which is aerated in the aerobic section (10.1) and the C u is removed in the upper layer, comes to the lower layer, which is the anaerobic I anoxic section (10.2), where the oxygen-free anaerobic I anoxic section (10.2) is at the bottom, NO3s will turn into N2 gas by denitrification, thus C and nitrogen double layer vertical purification it will be removed from the wastewater in one unit containing the boiler (10). For these reasons, the investment and operating costs of our invention are lower. Thus, problems in the known technique are eliminated.

Another problem in conventional systems is the need to add expensive organic C source (methanol) externally for denitrification. This situation occurs when there is not enough organic carbon source in the environment. The treatment system subject to our invention does not require an external organic carbon source. This is because the low molecular weight components generated during sludge digestion from the internal sludge cycle serve as C sources for denitrifying bacteria. For this reason, there is no need to add methanol externally in the system of our invention.

One of the biggest problems in conventional systems is waste sludge disposal. For this purpose, a sludge digester is built in the last part of every conventional system. Sludge digesters are units that require extra space-consuming pumping, and bring investment and partial operating costs. According to the treatment system of our invention, there is no need for an external digestion tank. Because the excess biomass and recycle sludge produced in the aerobic section (10.1 ) located in the ventilated upper layer of the treatment plant subject to our invention will decompose in the lower layer, which is the anaerobic I anoxic section (10.2), there is no need for an additional sludge digester. Thus, this problem in the known technique is solved. The gas (CF ) obtained during sludge digestion will be used. Thus, an extra tank is eliminated and additional energy is provided. Similarly, sludge dewatering is done in conventional systems and in the treatment systems subject to our invention. In both, the filtrate water from dewatering contains high inorganic phosphorus and is transferred to the entrance of the treatment plant.

In order to best explain and compare the invention, a VAASDWPS and CS for a settlement with a population of 10,000 were designed and compared:

Dimensions of the facility subject to our invention are:

Top Layer: (Aeration tank / settling layer)

Height (H) = 5 m

Surface area (YA) = 40 m2

Volume (V) = 194 m3 Diameter (D) = 7.1 m

Sub layer: (Anoxic I Anaerobic, Sludge digestion)

Height (H): 4.5 m

Surface area (YA) = 40 m2

Volume (V) = 100 m2

Diameter (D) = 7.1 m Final precipitation:

Height (H) = 3 m

Surface area (YA) = 64 m2

Volume (V) = 192 m3

Diameter (D) = 9 m

Total Area Required = 40 + 64 = 104 m2

Total volume required = 194 + 100 + 192 = 576 m3

System other components (Necessary additional equipment)

Elevation through pumping, sludge recycling, stabilized sludge removal

Processes to be achieved:

Carbon oxidation, nitrification, denitrification, advanced biological P removal

Dimensions of conventional systems are (Primary settling + aeration tank + final settling + Sludge digestion)

Primary settling:

Height (H) = 3 m

Surface area (YA) = 31 m2

Volume (V) = 93 m3

Diameter (D) = 6.3 m

Aeration tank I settling layer:

Height (H) = 5 m

Surface area (YA) = 40 m2

Volume (V) = 194 m3

Final Settling:

Height (H): 3.0m

Surface area (YA) = 64 m2

Volume (V) = 192 m3

Diameter (D) = 9.0 m Sludge digestion:

Height (H) = 4.5 m

Surface area (YA) = 40 m2

Volume (V) = 180 m3

Diameter (D) = 7.1 m

Total Area Required = 40 + 64 = 104 m2

Total volume required = 194 + 100 + 192 = 576 m3

System other components (Necessary additional equipment)

Promotion, sludge recycling, stabilized sludge removal

Processes to be achieved are;

Carbon oxidation, nitrification, denitrification, advanced biological phosphorus removal (without additional unit)

Required Space = 31 + 40 + 64 + 40 = 175 m2

Required volume = 93 + 194 + 192 + 180 = 669 m3

System other components (Necessary additional equipment)

5 pumping required:

Elevation through pumping, sludge recirculation, pre-settling sludge, stabilized sludge removal, sludge digester

Processes to be achieved are :

Carbon oxidation, nitrification

(in case of additional unit: denitrification, advanced biological phosphorus removal)

The need for promotion pumping: It is necessary for CS, but also for VAASDWPS.

The need for sludge recycle pumping is needed in CS, but also in VAASDWPS.

The need for stabilized sludge removal pumping is required in CS, but in VAASDWPS.

The need for primary settling sludge pumping is required in CS, not in VAASDWPS.

The need for sludge digesters pumping is necessary in CS, not in VAASDWPS. Separate C oxidation tank is needed in CS, not in VAASDWPS.

Separate Nitrification Tank need is needed in CS, not in VAASDWPS.

Separate Denitrification tank is needed in CS, not in VAASDWPS.

There is a need for a biological phosphorus removal tank in CS, not in VAASDWPS.

Biogas production needs additional reactor (sludge digestion): CS also needs, not VAASDWPS.

There is a need for pre-precipitation in CS, not in VAASDWPS.

Required space requirement (for the population in the problem): 175 m² in CS, 104 m² in VAASDWPS

Required volume is 669 m³ in CS, 576 m³ in VAASDWPS.

Claims

CLAIMS A single unit biological wastewater treatment plant without primary settling, with vertical aerobic I anaerobic sludge digestion characterized in that it comprises a vertical purification vessel (10) comprising at least one aerobic section (10.01 ) in the upper layer and at least one anaerobic I anoxic section (10.02) in the lower layer.