WO2022264164A1

WO2022264164A1 - A system and a process for simultaneous removal of ammoniacal nitrogen and oxidizable carbon (bio-sac) from wastewaters

Info

Publication number: WO2022264164A1
Application number: PCT/IN2022/050529
Authority: WO
Inventors: Anupoju GANGAGNI RAO; Kranti Kuruti; Sameena Begum; Sudharshan JUNTUPALLY; Arelli VIJAYALAKSHMI
Original assignee: Council Of Scientific And Industrial Research An Indian Registered Body Incorporated Under The Regn. Of Soc. Act (Act Xxi Of 1860)
Priority date: 2021-06-19
Filing date: 2022-06-07
Publication date: 2022-12-22

Abstract

Chemical and allied industry is scouting for a cost-effective solution in meeting the standards for ammoniacal nitrogen (AN) of 50 ppm. The present invention provides a sequential biological process (Bio-SAC) for simultaneous removal of COD and AN from industrial wastewaters. In the developed process, initially free ammonia from wastewater is stripped off using counter current air stripper and subsequently wastewater is subjected to a sequence of bioprocesses (aerobic, anoxic and anaerobic) with specially developed microbial consortia at optimized conditions (hydraulic residence time (HRT) of 8.5 hrs, pH of 7.0, recycle ratio of 1:1). Removal efficiency of 60 to 70 % in terms of AN and COD is obtained with the process from the initial levels of 250 to 500 mg/L AN & 40,000 to 45,000 mg/L of COD.

Description

A SYSTEM AND A PROCESS FOR SIMULTANEOUS REMOVAL OF AMMONIACAL

NITROGEN AND OXIDIZABLE CARBON (BIO-SAC) FROM WASTEWATERS

FIELD OF INVENTION

The present invention relates to a system and a process for the simultaneous removal of ammoniacal nitrogen (AN) and chemical oxygen demand (COD) from industrial wastewaters referred to as Bio-SAC process. In particular, the present invention relates to the development of a sequential process of stripping, aerobic and anoxic respiration followed by anaerobic digestion by using specially developed aerobic, anoxic and anaerobic microbial cultures in novel bioreactors. Another highlight of the process is the shorter residence time of 8.5 hrs using the cyclic biological process to achieve the removal efficiencies in the range of 60 - 70 % both in the case of AN and COD from industrial wastewaters. AN and COD can be simultaneously removed through sequential biological processes in the developed system. The process abbreviated as Bio-SAC would be used hence forth. The instant invention is useful for the removal of AN and COD simultaneously from wastewaters and still high treatment efficiency can be obtained with less operating and capital costs compared to the existing systems. The developed system finds immense application in the field of waste water treatment.

BACKGROUND OF THE INVENTION

Removal of COD and AN from industrial and domestic wastewaters is highly essential to meet the disposal concentration limits stipulated by the regulatory bodies for the safe disposal of waste waters. Numerous methods are available for the removal of carbon matter (COD) from domestic and industrial wastewaters. Similarly, there are many physico-chemical and biological methods such as mechanical separation, membrane filtration, ammonia stripping, Ion exchange; breakpoint chlorination, electro dialysis, struvite precipitation, nitrification and denitrification to remove AN from industrial wastewaters. Generally, in the effluent treatment scheme, unit operations for COD and AN removal are in the sequence; COD removal precedes the AN removal. In order to remove AN and COD in wastewater, biological methods are commonly preferred due to lower input energy requirement and the operation and maintenance cost.

Ammonia is widely used in the chemical industry as a cleaning and bleaching agent in the production of chemicals, fertilizers, plastics, explosives etc. As a result, large quantities of wastewater containing AN along with COD are produced. Conventional biological (nitrification & de-nitrification) wastewater treatment systems for nitrogen removal requires a lot of energy to create aerobic conditions for nitrification and also requires organic carbon to remove nitrate by de-nitrification. The sequence of process demands external carbon source in denitrification since the COD of the wastewater gets removed simultaneously in the nitrification step which precedes de-nitrification.

An alternative approach is the use of anoxic anammox process. Anammox, an abbreviation for ANaerobic AMMonium Oxidation, is a globally important microbial process of the nitrogen cycle. The bacteria mediating this process were identified only 20 years ago. It takes place in many natural environments and anammox (Strous et al 1999) is also the trademarked name for an ammonium removal technology that was developed by the Delft University of Technology. Chemo litho autotrophic bacteria belonging to the order planctomycetales perform the Anammox. Anammox bacterium grows extremely slowly, multiplying only once in a week. Thus it is difficult to cultivate this bacterium by conventional microbiological techniques. Further, there is limited information on physiological characteristics of this bacterium. Therefore extensive information is important for practical application. Anammox is a cost effective, robust and sustainable way of removing ammonium from wastewater. Compared to conventional nitrification/de- nitrification process, operational costs, sludge output are reduced by 90% and consequent CO₂ emission levels are also reduced. In the anammox reactor ammonium is converted to nitrogen gas. The reaction is executed by two different bacteria, which coexist in the reactor. Nitrification bacteria oxidize about half of the ammonium to nitrite while the Anammox bacteria convert the ammonium and nitrite into nitrogen gas. Anammox process is applicable to various industrial effluents such as municipal wastewater treatment (reject water from a sludge digester), organic solid waste treatment plants (landfills, composting, digestion), food industry, manure processing industry, fertilizer industry, petrochemical industry, metal and mining industry etc,.

The anammox, though is an emerging method but it is proven to be promising only in a few full-scale installations in Europe. The first full scale reactor intended for the application of anammox bacteria was built in the Netherlands in 2002. Ten years later Paques’ (http//en.paques.nl 2016) installed atotal of 11 full-scale anammox plants. Paques’ experience of over twenty years in the design, construction and operation of biological wastewater treatment plants has resulted in an anammox reactor that combines excellent biomass retention and granule formation with very good mixing. Effective conversion and stable operation are therefore guaranteed. This technology therefore makes sewage water treatment a net energy producer and also ensures that nutrients (such as ammonium and nitrate) are effectively removed. Majority of the energy-saving treatment concepts fail to meet the objective of nutrient removal.

The application of anammox bacteria can be further improved by optimizing such reactor systems through the use of genomics-based microarrays to monitor gene expression under various environmental conditions relevant to wastewater practice (shock loads, periods of starvation, oxygen inhibition). Further aspects currently under active discussion are a comparison of reactor configurations and process control options: single-stage vs. two- stage reactors (i.e. with segregated nitrification and anammox stages), suspended growth vs. attached biofilm or granular reactors, selection of sensors required for process control and a detailed strategy for embedding these sensors in automated process control systems are among the topics most actively pursued both in the laboratory and in full-scale operation. Even though great potential exists for this process in India, limited research work was carried out mainly in IIT-Chennai, Anna University-Chennai (PC Sabumon 2007; Suneethi et al.,2011) and NEERI (Shivaraman S. and Geetha S, 2004). Although good amount of work has been carried out and it is understood that due to the complexity of the wastewaters generated from the Indian chemical and allied industries, a comprehensive approach is necessary instead of a single stage anammox process. Reference may be made to US8637304 B1 which recites a process to recover nitrogen from liquid waste using autotrophic organisms with minimal energy inputs and without chemical additives. Solids are separated from anaerobically digested liquid waste. The resultant translucent liquid is introduced to a culture of autotrophic microorganisms in the presence of natural or artificial light, thereby accumulating the biomass and producing a liquid effluent with elevated pH. The liquid effluent at an elevated-pH is heated and stripped of ammonia, thereby producing water vapour and stripped ammonia gas stream. The water vapour, ammonia gas stream is condensed to form a liquid/ ammonia condensate. However, the limitations of this process are that it requires light energy for the conversion of ammonia into vapour and leads to air pollution.

Reference may be made to US 8911628 B2, wherein the wastewater is purified in an aeration tank in which a low oxygen concentration of less than 1.0 mg/1 is set so as to first convert the ammonium contained in the waste water to nitrite using the aerobic oxidizing bacteria while the conversion of ammonium and nitrite to elemental nitrogen is done using the anaerobic oxidizing bacteria. At least a part of surplus sludge formed in the aeration tank is separated into a dense sludge phase and a light sludge phase. The light sludge phase is fed as surplus sludge to a sludge digestion. Sludge water that is separated from the sludge in a sludge dewatering is fed to a de-ammonifying tank. Nitrogen compounds in the sludge water are converted, by de-ammonification in the de-ammonifying tank, to elemental nitrogen. However, the limitations of this process are that it requires higher amount of energy for aeration and sludge separation in each phase is also an issue.

Reference may be made to WO 2014043547 Al, wherein one or more reactor and one or more control methods are used for nitrogen removal in wastewater treatment to achieve measured control of high ammonia oxidizing bacteria (AOB) oxidation rates while achieving nitrite oxidizing bacteria (NOB), using various control strategies, including: I) ammonia and the use of ammonia set points; 2) operational DO and the use of DO set points; 3) bioaugmentation of anammox and lighter flocculant AOB fraction; and 4) implementation of transient anoxia in several reactor configurations and conditions for the removal of oxidized nitrogen using anammox or heterotrophic organisms. Controls described maximize nitrogen removal with minimal aeration, through control of transient anoxia and aerobic SRT, out-selection of NOB, and control of DO concentrations or aeration. However, the above operation containing so many controlling units as well as increasing the unit operation mechanism which leads to the increase of the maintenance costs.

Reference may be made to KR 20040099595 A, wherein extra unit operations such as filtration and sedimentation are required. No process parameters have been mentioned in the said disclosure. It relates to anaerobic followed by aerobic process for the removal of NO₃-N and phosphate release. After the anaerobic reaction of the batch anaerobic tank is finished, it is introduced into the continuous batch reactor to the lower portion of the filter medium. After completion of the aerobic reaction, precipitating MLSS present in the floating region (13) to perform solid-liquid separation. When the sedimentation step is completed, the supernatant is discharged, and a part of the sludge is discarded, and the rest is repeatedly performed three to four times a day as a treatment step which flows into the batch anaerobic tank again.

Reference may be made to CN 203741114U which discloses an anaerobic biological treatment device for high-COD and high-ammonia- nitrogen industrial wastewater. The device comprises of a UASB reaction tank and an Anammox reaction tank, wherein the UASB reaction tank comprises of a first three-phase separator arranged at the top of the UASB reaction tank and a first water distributor arranged at the bottom of the UASB reaction tank, wherein the first water distributor is connected to sewage pipes by a pipeline valve, an overflow outlet is arranged at the top of the UASB reaction tank and is connected to a reservoir by a valve and a pipeline; the Anammox reaction tank comprises a second three-phase separator arranged at the top of the Anammox reaction tank and a second water distributor arranged at the bottom of the Anammox reaction tank, wherein the second water distributor is connected with the reservoir, the second water distributor is connected to the bottom of the reservoir by a valve and the reservoir is provided with a liquid level sensor. However, the model proposed in the above patent is very complex in design and is very difficult to be used in practical applications on-site.

Reference may be made to US 7820047 B2 which recites a system that has two separate but interlinked tanks containing four different zones, namely aerobic, microaerophilic, anoxic and anaerobic, for the biological treatment of the wastewater, as well as two clarification zones and a filtration unit for the separation of solids from liquid. The first tank contains the aerobic, microaerophilic and anoxic zone as well as a clarification zone, while the second tank includes the anaerobic zone, a solid-liquid separation zone and a filtration unit. The aerobic zone is an airlift reactor that contains air diffusers at the bottom of the zone to introduce air into the zone. The air bubbles mix the liquid and its content with microorganisms, and provide oxygen for the aerobic biological processes to take place in this zone. Aeration also produces circulation of liquid between the aerobic zone and its adjacent microaerophilic and anoxic zones that are located at the sides and raider the aerobic zone, respectively. The aerobic zone contains suspended microorganisms of heterotrophic and autotrophic groups that grow inside the circulating liquid, known as mixed liquor. Within the volume of the aerobic zone, loose earlier material or stationary objects are disposed to support the attachment of microbial biomass and the formation of microbial biofilm.

Reference may be made to WO 1995019322 Al, which discloses treatment using anaerobic followed by anoxic and aerobic process. It’s a counter flow process wherein the wastewater flows in one direction and the sludge flows in opposite direction. Application of additional unit operations such as electric current, magnetic field, coagulation-flocculation means, oxidation-reduction means, adsorption means and biostimulators. No process parameters have been mentioned in the said disclosure.

Reference may be made to WO 201200062 Al wherein the removal of carbon and nitrogen contaminants from the wastewater in one step is provided. A mixture of heterotrophic nitrification-aerobic denitrification bacteria and activated sludge at a defined ratio is inoculated in a single biochemical reactor. When aeration is carried out for a defined time, nitrogen and organic matter are removed, simultaneously. The removal of nitrogen and carbon has high efficiency.

Despite all the above, an unmet need still exists to develop an integrated process for the simultaneous removal of around 60 to 70 % ammoniacal nitrogen [AN] and chemical oxygen demand [COD] from industrial wastewaters.

Therefore, keeping in view the drawbacks of the hitherto reported prior art, the inventors of the present invention realized that there exists a dire need to provide a system and a process for simultaneous removal of AN and COD from wastewaters comprising the sequential process of stripping, aerobic and anoxic respiration followed by anaerobic digestion by using specially developed aerobic, anoxic and anaerobic microbial cultures in novel bioreactors, wherein the process has a short residence time of 8.5 hrs using the cyclic biological process to achieve the removal efficiencies in the range of 60 - 70 % both in the case of AN and COD from industrial wastewaters.

OBJECTIVES OF THE INVENTION

The main objective of the present invention is therefore to provide an innovative, robust, competitive, low cost system for the simultaneous removal of ammoniacal nitrogen (AN) and COD from industrial wastewaters which obviates the drawbacks of the hitherto reported prior art.

Another objective of the present invention is to provide a system and process for sequential biological treatment referred as BioSAC process of industrial waste waters having high chemical oxygen demand (COD) in the range of 500 to 40,000 mg/L and ammoniacal nitrogen (AN) in the range of 100 to 500 mg/L. Still another objective of the present invention is to provide a system for safe disposal of wastewaters meeting the environmental disposal standards in a short reaction time of 8.5 hrs.

Yet another objective of the present invention is to provide a system for sequential biological treatment in the presence of aerobic, anoxic and anaerobic microorganisms after stripping process for the oxidation of organic matter and simultaneous removal of ammoniacal nitrogen along with the generation of biogas in the last phase of the process.

Still another objective of the present invention is to provide a process for the simultaneous removal of AN and COD from industrial wastewaters wherein the Hydraulic Residence Time [HRT] is as short as 8.5 hours to achieve the removal efficiencies in the range of 60 - 70 % both in the case of AN and COD.

Yet another objective of the present invention is to provide a system and process which is suitable for the treatment of a wide variety of industrial waste waters.

SUMMARY OF THE INVENTION

The present invention relates to a system for the simultaneous removal of ammoniacal nitrogen and COD from industrial wastewaters. The invention further provides a novel sequential biological process (Bio-SAC) wherein AN and COD are simultaneously degraded to a great extent. Initially, the wastewater is subjected to stripping/aeration for 30 minutes to ensure the removal of free ammonia from the wastewater. Subsequently, the stripped wastewater free of ammonia is subjected to biological treatment under aerobic conditions for 3 hrs. The aerobic treatment of wastewater is required to adjust the AN to nitrite ratio. Later on, the aerobically treated waste water is exposed to anoxic environment for 2 hrs followed by anaerobic environment for 3 hrs.

The sequential biological treatment of wastewater under aerobic, anoxic and anaerobic conditions facilitates the conversion of 60 to 70 % of AN to nitrogen gas depending on the inlet AN concentration. During this sequential biological treatment, a simultaneous reduction in COD is also observed. About 60 to 70 % of the COD can be removed by its conversion to water and CO₂. Hence, the total process is completed in 8.5 hrs which indicates that the Bio-SAC process can be accomplished at a hydraulic residence time (HRT) of 8.5 hrs which makes the process economically attractive since the process could remove COD and AN simultaneously in a very short time.

The industrial wastewaters having COD as high as 40,000 mg/L and AN concentration ranging between 100 mg/L and 500 mg/L were treated using the developed process viz., the BioSAC process with a HRT of 8.5 hrs. The BioSAC process resulted in the reduction efficiencies between 60 and 70% for the simultaneous removal of COD and AN.

The entire BioSAC process is based on energy conservation from anaerobic oxidation of ammonium with nitrite as electron acceptor as well as carbon source (COD) in the wastewater. The instant innovation envisages the microbial conversion of AN to nitrogen under aerobi c/anoxic/ anaerobic conditions sequentially. This process requires less energy, the requirement of external chemicals is nil and the quantitative production of sludge is less as compared to the conventional treatment methods. The developed BioSAC process can be operated at ambient temperature and pressure under aerobic/anoxic/anaerobic conditions. Therefore, no input energy is required except for pumping the wastewater to the reactor. The system of the present invention can handle a variety of industrial wastewaters having high AN and COD of varying concentrations.

In an embodiment, the present invention provides a system for the treatment and simultaneous removal of ammoniacal nitrogen (AN) and chemical oxygen demand (COD) from the industrial waste waters comprising:

• a feed preparation tank (1), a stripping tank (3), an aerobic reactor (6), an anoxic reactor (8), an anaerobic reactor (10), a digestate collection (13);

• an effluent inlet mechanism from feed preparation tank (1) to the stripping tank through the slurry pump (2); • an air compressor (4) to supply clean air for 0.5 hrs at a controlled flow rate to the stripping tank to facilitate the conversion of ionized ammonia to free ammonia and its release to the atmosphere;

• an overflow transport mechanism from stripping tank (3) to the aerobic reactor (6), whereby through pumping (5) the stripped effluent is subjected to the action of aerobic microorganisms for the oxidation of the organic matter and the conversion of ammonium ions and free ammonia to nitrite and nitrates;

• a common air supply mechanism from the air compressor (4) to the aerobic reactor (6) which is open to air for the oxidation of the organic matter;

• a sparger (14) in the aerobic reactor (6) to provide even distribution of air in the aerobic reactor;

• an overflow transport mechanism from the aerobic reactor (6) to the anoxic reactor (8) partially open to atmosphere, whereby through pumping (7) the aerated effluent is passed to anoxic microorganisms for further removal of organic matter;

• an overflow transport mechanism from the anoxic reactor (8) to the anaerobic reactor (10) which is completely closed, whereby through pumping (9) the effluent from anoxic reactor is passed to anaerobic reactor having anaerobic microorganisms for the conversion of organic matter to biogas which is stored in biogas storage tank (12);

• an agitator (15) in the anaerobic reactor to ensure efficient mixing of the reactor contents inside the digester;

• a digestate collection tank (13) to collect final anaerobic digestate for the safe disposal meeting the environmental standards;

• a transport mechanism through digestate recirculation line (11) from the anaerobic digester (10) to recirculate the digestate in the ratio of 1:1 to the feed preparation tank (1) to ensure appropriate buffering and mixing of the influent in the feed preparation tank (1);

• a set of control valves and flow meters at each of the reactor and the pumping mechanism for the controlled flow of air and effluent. In another embodiment, the present invention provides a system, wherein the industrial effluent is sent to the feed preparation tank (1) wherein the effluent is adjusted for pH.

In still another embodiment, the present invention provides a system, wherein the effluent from the feed preparation tank is sent to the stripping tank (3) for the simultaneous conversion of ionized ammonia to free ammonia which is released in the atmosphere, through proper slurry pumping mechanism (2) by controlling the flow using the valves at normal temperature and pressure conditions.

In yet another embodiment, the present invention provides a system, wherein the stripping tank is provided with effluent drawing mechanism through pump (5) to allow the stripped effluent to overflow from stripping tank (3) to aerobic reactor (6).

In still another embodiment, the present invention provides a system, wherein the stripping tank is provided with the controlled air supply using an air compressor (4).

In yet another embodiment, the present invention provides a system, wherein the aerobic reactor is completely open to atmosphere and provided with a sparger (14) for the efficient distribution of controlled air supply from the air compressor (4) in the reactor, wherein further the aerobic reactor is provided with the effluent drawing mechanism through pump (7) to allow the flow of aerated effluent overflow to the anoxic reactor (8) which is partially open to atmosphere to control the oxygen levels inside the reactor.

In still another embodiment, the present invention provides a system, wherein the anoxic reactor is provided with the effluent drawing mechanism through pump (9) to allow the flow of anoxic effluent overflow to the anaerobic reactor (10) which is completely closed to create anaerobic environment, wherein further the anaerobic reactor is equipped with an agitator (15) to facilitate efficient mixing and the final digestate is drawn from the anaerobic reactor and collected in the digestate collection tank. In yet another embodiment, the present invention provides a system, wherein the anaerobic reactor (10) is provided with a recirculation line to the feed preparation tank to recirculate the digestate in 1 : 1 ratio to maintain appropriate buffering and mixing in the stripping tank.

In still another embodiment, the present invention provides a system, wherein the effluent inlet and outlet (withdrawal) mechanism is provided with valve mechanism either to feed or withdraw the effluent from each unit under standard temperature and pressure conditions

In yet another embodiment, the present invention provides a system, wherein the reactors are provided with sample collection ports and pH adjusting mechanism as per the desired pH. In still another embodiment, the present invention provides a system, wherein the aerobic reactor (6) has a provision to measure the dissolved oxygen level and wherein the dissolved oxygen level is maintained in the range of 0.3 - 0.5 mg/L.

In yet another embodiment, the present invention provides a system, wherein the pH adjusting mechanism comprises:

• a pH measuring probe for measuring the pH value of the effluent;

• a means for supplying a source of an acid to the effluent;

• a means for supplying a source of a base to the effluent; and

• a controller operably connected to the pH measuring probe for receiving a signal indicative of the pH value of the effluent and controlling an operation of the means for supplying the source of acid or the means for supplying the source of base so as to maintain the pH value of the slurry at a predetermined value.

In a further embodiment, the present invention provides a process for the simultaneous removal of ammoniacal nitrogen and chemical oxygen demand (COD) from the industrial waste waters containing high AN and COD within a short period of time using the developed system, wherein the method comprises the following steps: a) sending the industrial waste water to the feed preparation tank (1) which is pumped (2) to stripping tank (3); wherein the wastewater is subjected to air stripping for 0.5 hrs by suppling external air using an air compressor (4); b) stripping the waste water for 0.5 hrs to ensure the removal of ammoniacal nitrogen in the form of ammonia gas during the stripping process; c) pumping the wastewater from the stripping tank using slurry pump (5) to aerobic reactor (6) which is open to atmosphere; d) supplying clean air to the aerobic reactor through the air compressor and subjecting the wastewater to aeration for 3 hrs in the presence of aerobic inoculum to facilitate the removal of ammoniacal nitrogen and oxidation of the COD, wherein most of the free ammoniacal nitrogen in the form of N₂ and volatile organics in the form of CO₂ are released to the atmosphere in the stripping tank and the aeration reactor; e) providing the aerobic reactor with a sparger (14) to ensure proper mixing of the enriched aerobic, anoxic and anaerobic inoculum used in aerobic, anoxic and anaerobic reactors respectively, wherein the aerobic microbial consortia grows in this reactor using the oxygen from the air and organic present in the wastewater, wherein part of the organic matter is utilized for growth and some part is converted to CO₂ using the regular aerobic oxidation path leading to the conversion of some part of the organic matter (COD and BOD) in this reactor in 3 hrs hydraulic residence time (HRT), wherein in this reactor, part of ammoniacal nitrogen is converted to nitrite and nitrate and during this process ammoniacal nitrogen to nitrite ratio is adjusted to the new equilibrium which is optimum for subsequent processes, wherein the wastewater containing ionized ammonia (NH₄ ⁺) and free ammonia (NH₃) is converted to nitrite and nitrate during the aeration process; f) subjecting the wastewater to anoxic (2 hrs) / anaerobic (3 hrs) biological treatment to convert the ammoniacal nitrogen to nitrogen gas so that wastewater is free from ammoniacal nitrogen to the extent of 60 to 70% depending on the inlet ammoniacal nitrogen concentration, wherein during this course of treatment simultaneously chemical oxygen demand (COD) also gets removed to the extent of (60 to 70%) in the form of water and CO₂; g) pumping the aerated wastewater from the aerobic reactor to the anoxic reactor (8) which is partially open to atmosphere and subjecting to anoxic inoculum with an HRT of 2 hrs to further enhance the removal of COD from the wastewater; h) maintaining the required dissolved oxygen (DO) level in the anoxic reactor between 0.3 and 0.5 mg/L by controlled opening of the reactor lid; i) pumping the effluent from anoxic reactor to anaerobic reactor (9) which is equipped with an agitator (15) to allow efficient mixing of reactor contents, where anaerobic digestion of remaining organic matter takes place at an HRT of 3 hrs; j) collecting the digestate from the anaerobic reactor in the digestate collection tank

(13); k) recirculating the digestate to the feed preparation tank to ensure efficient buffering inside the system through the digestate recirculation line (11); l) storing the biogas generated from the anaerobic reactor in the biogas storage tank (12), wherein the digestate from the digestate collection tank at the end is disposed off safely while the biogas is useful for desired purposes.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The design features and the advantages of the present invention can be better understood when the following detailed description is read with reference to the process flow diagram as presented in Figure 1.

Skilled artisans would appreciate that the elements in the drawing are illustrated for simplicity and may not have been necessarily drawn to scale. For example, the dimensions of some of the elements in the drawings may be exaggerated relative to other elements to assist in further understanding of design aspects of the present invention. Furthermore, one or more elements may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skilled in the art having benefit of the description herein.

FIGURE 1 is a view of embodiment of a SEQUENTIAL BIOLOGICAL PROCESS (Bio- SAC) in accordance with the present invention. This embodiment comprises of a feed preparation tank (1), stripping tank (3), aerobic reactor (6), anoxic reactor (8), anaerobic reactor (10, an air compressor (4), slurry pumps (5, 7 and 9), biogas storage tank (12) and the digestate collection tank (13). The aerobic reactor is equipped with a sparger (14) and the anaerobic reactor is equipped with an agitator (15).

The industrial wastewater is sent to the feed preparation tank (1) which is pumped (2) to stripping tank (3) where the wastewater is subjected to air stripping for 0.5 hrs by supplying external air using an air compressor (4). The effluent in the feed preparation tank is adjusted for pH using suitable chemicals before pumping the effluent to the stripping tank. This depends on the initial pH of the wastewater and in many cases, it is required only during the first cycle since in the subsequent phases recycle is mixed with fresh wastewater that makes the pH to neutral which is the requirement. The waste water is stripped for 0.5 hrs to ensure the removal of ammonia nitrogen in the form of ammonia gas during the stripping process. The wastewater from the stripping tank is then pumped using slurry pump (5) to aerobic reactor (6) which is open to atmosphere. The aerobic reactor is also supplied with clean air through the air compressor and the waste water is subjected to aeration for 3 hrs in the presence of aerobic inoculum to facilitate the removal of ammonia nitrogen and oxidation of the COD. The aerobic reactor is provided with a sparger to ensure proper mixing Specially enriched aerobic, anoxic and anaerobic inoculum will be used in aerobic, anoxic and anaerobic reactors respectively. Subsequently, the aerated wastewater from the aerobic reactor is then pumped to the anoxic reactor (8) which is partially open to atmosphere and subjected to anoxic inoculum with reaction time (RT) of 2 hrs to further enhance the removal of COD from the waste water. In the anoxic reactor, redox reactions take place while in the aerobic reactor only oxidation occurs. The required dissolved oxygen (DO) level in the anoxic reactor is between 0.3 and 0.5 mg/L. So, the required DO level in the anoxic reactor would be maintained by controlled opening of the reactor lid and measurement of the DO in the reactor is determined by the mobile DO meter. The effluent from anoxic reactor is then pumped to anaerobic reactor (9) which is equipped with a mixer where anaerobic digestion of remaining organic matter takes place. The RT of the anaerobic reactor is 3 h. The digestate from the anaerobic reactor is collected in the digestate collection tank (13). The digestate is recirculated in the ratio of 1:1 to the feed preparation tank partially to ensure efficient buffering and mixing inside the system through the digestate recirculation line (11). The biogas generation from the anaerobic reactor is stored in the biogas storage tank (12).

Valves are provided at suction and discharge of each pump to control the flow as well as to isolate any chamber for maintenance reasons. Feed preparation tank (1) and all the chambers (3, 6, 8 & 10) are provided with suitable drain outlet and sample collection ports for emergency opening or maintenance and sample collection respectively. As shown in the FIGURE 1, All the components of the BioSAC that are in contact with waste and the aerobic, anoxic and anaerobic microorganisms are made of non-corrosive materials, e.g. stainless steel (SS). DETAILS OF BIOLOGICAL RESOURCES USED IN THE INVENTION

The present invention uses both aerobic as well as anaerobic microorganisms individually as well as in consortium. The details thereof are being provided here as under:

Note:

It is further to mention that the entire experimentation is not strain specific of the microbes used. These microbes used are widely available and accessible to public from the appropriate sewage sources including the source and location mentioned in the table above. There is no modification or alteration has been made at their gene level or strain level to restrict public from accessing the same. DETAILED DESCRIPTION OF THE INVENTION

The detailed description of the preferred embodiment is provided herein. It can be understood, that the present invention may be embodied in various forms. Therefore, the specific details disclosed herein are not to be interpreted as limitation, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or manner.

While the invention is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the invention as defined by the appended claims.

The terms "comprise", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that one or more devices or sub-systems or elements or structures proceeded by "comprises... a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or additional devices or additional sub-systems or additional elements or additional structures. Similarly, a method step proceeded by “comprising” or any variation thereof, does not, without more constraints preclude the existence of additional steps or repetitive steps.

FIGURE 1 is a view of embodiment of a SEQUENTIAL BIOLOGICAL PROCESS abbreviated as Bio-SAC in accordance with the present invention.

This embodiment comprises of a feed preparation tank (1), stripping tank (3), aerobic reactor (6), anoxic reactor (8), anaerobic reactor (10), an air compressor (4), slurry pumps (5, 7 and 9), biogas storage tank (12) and the digestate collection tank (13). The aerobic reactor is equipped with a sparger (14) and the anaerobic reactor is equipped with an agitator (15).

Referring to Figure 1, the industrial waste water is sent to the feed preparation tank (1) which is pumped (2) to stripping tank (3) where the wastewater is subjected to air stripping for 0.5 hrs by suppling external air using an air compressor (4). The effluent in the feed preparation tank is adjusted for pH using suitable chemicals before pumping the effluent to the stripping tank. The waste water is stripped for 0.5 hrs to ensure the removal of ammonia nitrogen in the form of ammonia gas during the stripping process as shown in the equation (Eq. (1)).

The wastewater from the stripping tank is then pumped using slurry pump (5) to aerobic reactor (6) which is open to atmosphere. The aerobic reactor is also supplied with clean air through the air compressor and the wastewater is subjected to aeration for 3 hrs in the presence of aerobic inoculum to facilitate the removal of ammoniacal nitrogen and oxidation of the COD. Most of the free ammoniacal nitrogen in the form of N₂ and volatile organics in the form of C0₂ are released to the atmosphere in the stripping tank and the aeration reactor. The aerobic reactor is provided with a sparger (14) to ensure proper mixing. Specially enriched aerobic, anoxic and anaerobic inoculum are used in aerobic, anoxic and anaerobic reactors respectively. The aerobic microbial consortia grows in this reactor using the oxygen from air and organic present in the wastewater. Part of the organic matter is utilized for growth and some part is converted to C0₂ using the regular aerobic oxidation path. As a result, some part of the organic matter (COD and BOD) is converted in this reactor. The hydraulic residence time (HRT) of this reactor is 3 hrs. In this reactor, part of ammoniacal nitrogen is converted to nitrite and nitrate and during this process ammoniacal nitrogen to nitrite ratio is adjusted to the new equilibrium which is optimum for subsequent processes. Waste water contains ionized ammonia (NH₄ ⁺) and the free ammonia (NH₃) which is converted to nitrite and nitrate during the aeration process as per the equations given below (Eq. 2 and 3).

Subsequently, the wastewater is subjected to anoxic (2 hrs) / anaerobic (3 hrs) biological treatment to convert most of the ammoniacal nitrogen via nitrite and nitrate route to nitrogen gas; so that wastewater is free from ammoniacal nitrogen to the extent of 60 to 70% depending on the inlet ammoniacal nitrogen concentration. During this course of treatment, simultaneously chemical oxygen demand (COD) also gets removed to the extent of (60 to 70%) in the form of water and CO₂. Subsequently, the aerated waste water from the aerobic reactor is then pumped to the anoxic reactor (8) which is partially open to atmosphere and subjected to anoxic inoculum with reaction time (RT) of 2 hrs to further enhance the removal of COD from the wastewater. In the anoxic reactor, redox reactions take place, while in the aerobic reactor only oxidation occurs. The required dissolved oxygen (DO) level in the anoxic reactor is between 0.3 and 0.5 mg/L. So, the required DO level in the anoxic reactor is maintained by controlled opening of the reactor lid and measurement of the DO in the reactor is determined by the mobile DO meter.

The effluent from anoxic reactor is then pumped to anaerobic reactor (9) which is equipped with an agitator (15) to allow efficient mixing of reactor contents where anaerobic digestion of remaining organic matter takes place. The RT of the anaerobic reactor is 3 h. Hence, total process is completed in a cycle of 8 and half hours which means the Bio-SAC process can be operated at an HRT of 8.5 hrs only making the process economically attractive.

The digestate from the anaerobic reactor is collected in the digestate collection tank (13). The digestate is recirculated in the ratio of 1 : 1 to the feed preparation tank partially to ensure efficient buffering and mixing inside the system through the digestate recirculation line (11). The biogas generated from the anaerobic reactor is stored in the biogas storage tank (12). The digestate from the digestate collection tank at the end can be disposed off safely while the biogas can be either used for purging or flared off.

Valves are provided at suction and discharge of each pump to control the flow as well as to isolate any chamber for maintenance reasons. Feed preparation tank (1) and all the chambers (3, 6, 8 & 10) are provided with suitable drain outlet and sample collection ports for emergency opening or maintenance and sample collection respectively. As shown in Figure 1, all the components of the BioSAC that are in contact with waste and the aerobic, anoxic and anaerobic microorganisms are made of non-corrosive materials, e.g. stainless steel (SS). The industrial wastewaters having 1.0 to as high as 40, 000 mg/L of COD with ammoniacal nitrogen of 100 mg/L to 500 mg/L can be handled by the developed system, wherein the reduction efficiency as high as 60 to 70 % is obtained for COD as well for ammoniacal nitrogen. The process is based on energy conservation from anaerobic oxidation of ammonium with nitrite as electron acceptor as well as carbon source (COD) in the wastewater. The present invention envisages the microbial conversion of ammoniacal nitrogen to nitrogen under sequential aerobic, anoxic and anaerobic conditions. The process requires less energy, no need for added chemicals and produces less sludge compared to the conventional treatment. The technology operates at ambient temperature and pressure under aerobic/ anoxic/anaerobic conditions. Accordingly, no energy consumption in the reactor is anticipated except for pumping the wastewater to the reactor. The system developed in the present invention is capable of handling a wide variety of industrial wastewaters having high ammoniacal nitrogen and COD of varying concentrations.

EXAMPLES

The functioning of the BioSAC system in accordance with the teachings of the present invention is described with reference to the following examples, which are explained by way of illustration only and therefore should not be construed to limit the scope of the present invention in any manner.

EXAMPLE: 1

> Process: Air stripping followed by aerobic, anoxic & anaerobic cyclic process

> Wastewater: Designed Synthetic Wastewater (DSW) > Operation strategy: 30 mints of air stripping followed by 3hrs of aeration, 2hrs of anoxic and 3 hrs of anaerobic process. This completes on cycle of operation. The cycles could be repeated for continuous operation.

> In each cycle fresh feed and recycle (treated wastewater) are mixed in 1: 1 ratio

> Reactor capacity:30 L; working volume - 20 L, pH - 7, Temperature - ambient

EXAMPLE: 2

> Process: Air stripping followed by aerobic, anoxic & anaerobic cyclic process

> Wastewater: Wastewater from M/s Lee Pharma, Bulk Drug Industry

> Operation strategy: 30 mints of air stripping followed by 3hrs of aeration, 2hrs of anoxic and 3 hrs of anaerobic process. This completes on cycle of operation. The cycles could be repeated for continuous operation.

> Reactor capacity:30 L; working volume - 20 L, pH - 7, Temperature - ambient

EXAMPLE: 3

> Process: Air stripping followed by aerobic, anoxic & anaerobic cyclic process > Wastewater: Wastewater from M/s Vizag Steel Plant, Coke oven Battery

Wastewater

> Operation strategy: 30 mints of air stripping followed by 3hrs of aeration, 2hrs of anoxic and 3 hrs of anaerobic process. This completes on cycle of operation. The cycles could be repeated for continuous operation. > In each cycle fresh feed and recycle (treated wastewater) are mixed in 1: 1 ratio

> Reactor capacity:30 L; working volume - 20 L, pH - 7, Temperature - ambient

EXAMPLE: 4

> Performance of air stripping followed by aerobic , anoxic & anaerobic cyclic process with SMS effluent

> Batch reactors: operation strategy: 30 mints of air stripping followed by 3hrs of aeration, 2hrs of anoxic and 3 hrs of anaerobic.

> Cyclic observation

> Before stripping Fresh 50% of effluent added for every cycle.

> Capacity: 30 L ; working volume - 20 L ,pH - 7, Temperature - ambient

ADVANTAGES OF THE INVENTION

• The developed sequential biological treatment referred as BioSAC process of industrial waste waters having high chemical oxygen demand (COD) in the range of 500 to 40,000 mg/L and ammoniacal nitrogen (AN) in the range of 100 to 500 mg/L for safe disposal meeting the environmental disposal standards requires a short reaction time of 8.5 hrs.

• Provision of feed preparation tank to adjust the pH using suitable chemicals or recycle before pumping the effluent to the stripping tank. · The removal of free ammonia from the wastewaters using air stripping process is done within 0.5 hrs of the total process time. • A sequential biological treatment in the presence of specially developed aerobic, anoxic and anaerobic microorganisms followed by stripping process for the oxidation of organic matter and simultaneous removal of ammoniacal nitrogen along with the generation of biogas in the last phase of the process.

• Achievement of COD and AN removal efficiency in the range of 60 - 70 % from the complex effluents and even more in the case of less complex effluents.

• Completion of oxidation process for the conversion of ionized ammonia to nitrite followed by nitrate in the aerobic reactor with a reaction time of 3 hrs.

• Completion of the anoxic process for the partial removal of COD in the anoxic reactor with a reaction time of 2 hrs.

• Completion of anaerobic digestion of the remaining organic matter (COD and other volatile organics) with a reaction time of 3 hrs along with the generation of biogas and digestate.

• Elimination of choking and clogging completely in the aerobic, anoxic and anaerobic reactors.

• The process equipment design is suitable for a wide variety of industrial waste waters.

Claims

We claim:

1. A system for the treatment and simultaneous removal of ammoniacal nitrogen

(AN) and chemical oxygen demand (COD) from the industrial waste waters comprising:

• an effluent inlet mechanism from feed preparation tank ( 1 ) to the stripping tank through the slurry pump (2);

• an air compressor (4) to supply clean air for 0.5 hrs at a controlled flow rate to the stripping tank to facilitate the conversion of ionized ammonia to free ammonia and its release to the atmosphere;

• a set of control valves and flow meters at each of the reactor and the pumping mechanism for the controlled flow of air and effluent.

2. The system as claimed in claim 1, wherein the industrial effluent is sent to the feed preparation tank (1) wherein the effluent is adjusted for pH.

3. The system as claimed in claim 1, wherein the effluent from the feed preparation tank is sent to the stripping tank (3) for the simultaneous conversion of ionized ammonia to free ammonia which is released in the atmosphere, through proper slurry pumping mechanism (2) by controlling the flow using the valves at normal temperature and pressure conditions.

4. The system as claimed in claim 1, wherein the stripping tank is provided with effluent drawing mechanism through pump (5) to allow the stripped effluent to overflow from stripping tank (3) to aerobic reactor (6).

5. The system as claimed in claim 1, wherein the stripping tank is provided with the controlled air supply using an air compressor (4).

6. The system as claimed in claim 1, wherein the aerobic reactor is completely open to atmosphere and provided with a sparger (14) for the efficient distribution of controlled air supply from the air compressor (4) in the reactor, wherein further the aerobic reactor is provided with the effluent drawing mechanism through pump (7) to allow the flow of aerated effluent overflow to the anoxic reactor (8) which is partially open to atmosphere to control the oxygen levels inside the reactor.

7. The system as claimed in claim 1, wherein the anoxic reactor is provided with the effluent drawing mechanism through pump (9) to allow the flow of anoxic effluent overflow to the anaerobic reactor (10) which is completely closed to create anaerobic environment, wherein further the anaerobic reactor is equipped with an agitator (15) to facilitate efficient mixing and the final digestate is drawn from the anaerobic reactor and collected in the digestate collection tank.

8. The system as claimed in claim 1, wherein the anaerobic reactor (10) is provided with a recirculation line to the feed preparation tank to recirculate the digestate in 1 : 1 ratio to maintain appropriate buffering and mixing in the stripping tank.

9. The system as claimed in claim 1, wherein the effluent inlet and outlet (withdrawal) mechanism is provided with valve mechanism either to feed or withdraw the effluent from each unit under standard temperature and pressure conditions.

10. The system as claimed in claim 1, wherein the reactors are provided with sample collection ports and pH adjusting mechanism as per the desired pH.

11. The system as claimed in claim 1, wherein the aerobic reactor (6) has a provision to measure the dissolved oxygen level and wherein the dissolved oxygen level is maintained in the range of 0.3 - 0.5 mg/L. The system as claimed in claim 1 , wherein the pH adjusting mechanism comprises:

• a pH measuring probe for measuring the pH value of the effluent;

• a means for supplying a source of an acid to the effluent;

• a means for supplying a source of a base to the effluent; and

• a controller operably connected to the pH measuring probe for receiving a signal indicative of the pH value of the effluent and controlling an operation of the means for supplying the source of acid or the means for supplying the source of base so as to maintain the pH value of the slurry at a predetermined value. 13. A process for the simultaneous removal of ammoniacal nitrogen and chemical oxygen demand (COD) from the industrial waste waters containing high AN and COD within a short period of time using the system as claimed in claim 1, wherein the method comprises the following steps: a) sending the industrial waste water to the feed preparation tank (1) which is pumped (2) to stripping tank (3); wherein the wastewater is subjected to air stripping for 0.5 hrs by suppling external air using an air compressor (4); b) stripping the waste water for 0.5 hrs to ensure the removal of ammoniacal nitrogen in the form of ammonia gas during the stripping process; c) pumping the wastewater from the stripping tank using slurry pump (5) to aerobic reactor (6) which is open to atmosphere; d) supplying clean air to the aerobic reactor through the air compressor and subjecting the wastewater to aeration for 3 hrs in the presence of aerobic inoculum to facilitate the removal of ammoniacal nitrogen and oxidation of the COD, wherein most of the free ammoniacal nitrogen in the form of N₂ and volatile organics in the form of CO₂ are released to the atmosphere in the stripping tank and the aeration reactor; e) providing the aerobic reactor with a sparger (14) to ensure proper mixing of the enriched aerobic, anoxic and anaerobic inoculum used in aerobic, anoxic and anaerobic reactors respectively, wherein the aerobic microbial consortia grows in this reactor using the oxygen from the air and organic present in the wastewater, wherein part of the organic matter is utilized for growth and some part is converted to CO₂ using the regular aerobic oxidation path leading to the conversion of some part of the organic matter (COD and BOD) in this reactor in 3 hrs hydraulic residence time (HRT), wherein in this reactor, part of ammoniacal nitrogen is converted to nitrite and nitrate and during this process ammoniacal nitrogen to nitrite ratio is adjusted to the new equilibrium which is optimum for subsequent processes, wherein the wastewater containing ionized ammonia (NH₄ ⁺) and free ammonia (NH₃) is converted to nitrite and nitrate during the aeration process; f) subjecting the wastewater to anoxic (2 hrs) / anaerobic (3 hrs) biological treatment to convert the ammoniacal nitrogen to nitrogen gas so that wastewater is free from ammoniacal nitrogen to the extent of 60 to 70% depending on the inlet ammoniacal nitrogen concentration, wherein during this course of treatment simultaneously chemical oxygen demand (COD) also gets removed to the extent of (60 to 70%) in the form of water and CO₂; g) pumping the aerated wastewater from the aerobic reactor to the anoxic reactor (8) which is partially open to atmosphere and subjecting to anoxic inoculum with an HRT of 2 hrs to further enhance the removal of COD from the wastewater; h) maintaining the required dissolved oxygen (DO) level in the anoxic reactor between 0.3 and 0.5 mg/L by controlled opening of the reactor lid; i) pumping the effluent from anoxic reactor to anaerobic reactor (9) which is equipped with an agitator (15) to allow efficient mixing of reactor contents, where anaerobic digestion of remaining organic matter takes place at an HRT of 3 hrs; j) collecting the digestate from the anaerobic reactor in the digestate collection tank (13); k) recirculating the digestate to the feed preparation tank to ensure efficient buffering inside the system through the digestate recirculation line (11); l) storing the biogas generated from the anaerobic reactor in the biogas storage tank (12), wherein the digestate from the digestate collection tank at the end is disposed off safely while the biogas is useful for desired purposes.