WO2020152707A1

WO2020152707A1 - Heavy metal removal from industrial effluents by combination of aerobic and anaerobic treatment

Info

Publication number: WO2020152707A1
Application number: PCT/IN2020/050068
Authority: WO
Inventors: Vanita DR. PRASAD
Original assignee: Dr Prasad Vanita
Priority date: 2019-01-21
Filing date: 2020-01-21
Publication date: 2020-07-30

Abstract

: Heavy metal removal from industrial effluents by combination of aerobic and anaerobic treatment is a treatment method for the treating heavy sulphate concentration containing industrial effluent. More particularly, the present invention relates to the treatment of effluent obtained from viscose fibre manufacturing industries, inorganic chemical industries and dye making industries. The present invention relates to treatment of effluent containing heavy concentrations of sulphur and zinc using a combination of anaerobic bacterial consortium and aerobic bioreactors. Moreover, the results show a significantly higher reduction of concentrations of sulphate, zinc and heavy metals. The present invention provides a highly efficient, plant scale method that is an alternative to an expensive physicochemical approach or a less efficient biological approach.

Description

TITLE: HEAVY METAL REMOVAL FROM INDUSTRIAL EFFLUENTS BY COMBINATION OF AEROBIC AND ANAEROBIC TREATMENT

FIELD OF INVENTION

The present invention relates to the treatment of industrial effluent. More particularly, the present invention relates to a process for the treatment of effluent obtained from Viscose manufacturing industries, Inorganic chemical industries and Dye manufacturing industries containing high concentrations of heavy metals as pollutants. The present invention relates to treatment of effluent from above mentioned industries containing a very high amount of Total Dissolved Solids such as sulphates and zinc heavy metals as pollutants. Moreover, the present invention also relates to reducing the concentration of water-soluble sulphates and ionic heavy metal species such as zinc, arsenic, cadmium, chromium, copper, lead and nickel contained in the industrial effluent.

The present invention more particularly relates to a biological process comprising a combination of aerobic and anaerobic treatability with aerobic and anaerobic granulated biomass to treat organic content of effluent having high sulphates and zinc concentration.

BACKGROUND OF THE INVENTION

Each year millions of gallons and more of contaminated wastewater are discharged as industrial wastes. This wastewater may contain a variety of contaminants, including sulphate and heavy metal species, substances which are objectionable from an environmental standpoint. Typical examples of industries which generate and discharge waste solutions containing contaminants such as those enumerated above include the chemical, metal processing and mining industries. Wastewater treatment and heavy metal pollution as a result of industrial activities are significant issues faced by many countries, especially developing ones. When heavy metals, such as arsenic, cadmium, chromium, copper, lead, nickel and zinc, contained in wastewater discharge into rivers and trenches without proper treatment, the result is severe pollution, leading to environmental impacts on aquatic life, plants and ecology.

The presence of sulphur compounds in water is usually an unacceptable factor. In the case of sulphate, sulphite and thiosulphate, the principal drawbacks are attack on the sewer, eutrophication and silting. In addition, heavy metals, which are particularly undesired because of their toxic properties, are frequently also present in water containing a large amount of sulphur compounds.

Industries which produce effluents containing sulphur compounds include the viscose and edible oils industry, tanning, paper, rubber, printing and photo graphic industries, metallurgic industry and mining industry.

Two types of method are available in general for the removal of sulphur- containing compounds, that is to say physicochemical methods and biological methods.

Physicochemical treatment methods include ion exchange and membrane filtration (electro dialysis and reverse osmosis). Disadvantages of such methods are the high costs and the large stream of waste which results. In the case of flue gas treatment, absorption on lime or ammonia is usually employed. In this case large amounts of gypsum or ammonium sulphate are formed; a part of these wastes could be re-used. However, particularly in the case of gypsum the possible uses are becoming ever fewer because the quality demands for gypsum are becoming ever more stringent. In the case of a biological treatment, sulphate, sulphite and other sulphur compounds are reduced by sulphur reducing bacteria in an anaerobic step to give sulphide, which in turn can be oxidized to elementary sulphur. The advantage of such a method is that only small waste streams remain because the sulphur formed can be re-used. However, the disadvantage is that, especially when the effluent contains little organic matter, electron donors have to be added in order to provide sufficient reduction equivalents for the sulphate -reducing bacteria (SRB). The most important electron donors are methanol, ethanol, glucose, hydrogen and carbon monoxide. The use of these or other electron donors has the effect of substantially increasing the cost of this method of removal of sulphur from waste streams.

There are number of processes used to effect removal of various contaminants. Such processes include gravity sedimentation, flotation, filtration, ion exchange, activated adsorption, reverse osmosis, electro dialysis, distillation and chemical precipitation. However, many of these processes are not ideally suited to treat large volumes of water or are excessively expensive to install and operate in comparison with their overall efficiency and effectiveness.

In addition to the above processes, various biological processes are known for removing contaminants from waste water solutions, including the removal of sulphate and heavy metals. In such processes sulphate reducing bacteria are employed to reduce the sulphate to hydrogen sulphide which in turn reacts with the heavy metals to form water insoluble heavy metal sulphide which precipitate out of solution. Typical examples of such known biological processes for removal of sulphate and heavy metal contaminants from aqueous processing waste streams or solutions include U.S. Pat. No. 4,354,937 and U.S. Pat. No. 4,108,722.

Drawbacks to the use of biological processes mentioned in above patents, include, the production of metabolic wastes which in and of themselves represent real or potential pollution problems and the formation of fine crystalline sulphide precipitates the removal of which, by sedimentation or filtration, is extremely difficult.

Biological process for removal of heavy metals in industrial wastewater involves the use of biological techniques for the elimination of pollutants from wastewater wherein, activated sludge (Aerobic biomass) is the most common option uses microorganisms in the treatment process to break down organic material with aeration and agitation, and then allows solids to settle out. However, the process is costly, energy negative and also generates large amount of secondary sludge whose management and disposal becomes another issue. Moreover, many previously known aerobic and anaerobic methods for the removal of sulphur are not suitable for plant scale removal of sulphur.

SUMMARY OF THE INVENTION

The principle object of the present invention is to resolve the problems and disadvantages of the conventional technologies as described hereinabove and to provide a method that relates to a biological process of bioremediation for the removal of very high concentration of sulphate, sulphide and zinc from industrial effluents obtained from viscose fibre manufacturing, chemical industries and dye making industries.

Another object of the present invention is to provide an efficient method of treatment for contaminated water comprising biological reduction of sulphate and zinc using a combination of anaerobic granulated bacterial consortium and aerobic bioreactors.

Another aspect of the present invention is optimizing standard operating conditions for removal of sulphates, sulphide and zinc from the industrial effluents with the help of bacterial consortium containing higher percent of sulphur reducing bacteria and the method comprising of a) Characterization of the industrial effluent; b) Setting up an scheme for treating effluent by a sustainable economical way of biological treatment using anaerobic granulated biomass and aerobic bioreactors.

Another aspect of the present invention is further directed to bioreactors system for treating sulphate containing effluent or water, comprising of plurality of bioreactor columns connected with each other, each of which comprises of (i) an inlet for introducing nutrients, (ii) an inlet for introducing feed solution comprising the sulphate containing effluent or water, (iii) an outlet for release of discharge effluent, (iv) characterization of the outlet discharge of the effluent.

In one of the aspects of the present invention, the sulphur or sulphate and sulphur- reducing bacteria include, but are not limited to: Acidianus convivator, Caldisphaera draconis, Halogeometricum rufum, Halorubrum cibi, Natronococcus occultus, Pyrococcus yayanosii, Vulcanisaeta moutnovskia, Desulfobulbus, Desulfobacter, Desulfovibrio, Desulfurmusa,

Thermodesulfobacteria, Archaeo globus, Methanobacterium curvum,

Methanobacterium congolense, Methanobacterium kanagiense,

Methanobacterium beijingense, Methanobacterium formicicum,

Methanobacterium uliginosum, Methanobacterium aarhusense,

Methanobacterium bryantii, Methanobacterium subterraneum, Methanobacterium palustre, Methanobacterium oryzae, Methanobrevibacter acididurans, Methanobrevibacter ruminantium, Methanobrevibacter gottschalkii,

Methanobrevibacter curvatus, Methanobrevibacter smithii, Methanocalculus taiwanensis, Methanocella paludicola, Methanococcoides methylutens, Methanoculleus receptaculi, Methanofollis ethanolicus, Methanolobus psychrophilus, Methanomethylovorans thermophila,

Methanomethylovorans hollandica, Methanosaeta concilii, Methanosaeta pelagica, Methanosaeta harundinacea, Methanosaeta thermophila,

Methanosarcina baltica, Methanosarcina barkeri, Methanosarcina siciliae, Methanosarcina vacuolate, Methanosarcina mazei, Methanosarcina acetivorans, Methanosphaera stadtmanae, Methanosphaera cuniculi, Methane spirillum hungatei

The present invention relates to the process of removing sulphates, sulphide, zinc and heavy metals compounds from the industrial effluent, wherein the effluent is subjected to a combination of aerobic and anaerobic treatment with bacteria, which usually comprise sulphate reducing bacteria, sulphate reducing bacteria oxidising compounds having carbon atoms, as well as methane producing bacteria.

According to another aspect, the present invention relates to anaerobic test for the biodegradation of the pollutants present in the fibre manufacturing industrial effluent when subjected to an anaerobic wastewater treatment plants (WTP) or effluent treatment plant (ETP). Moreover, in the determination of the biodegradability a distinction is made between the degradability of the effluent and toxicity to the sludge. The ultimate degradation is the complete conversion of the polluting components present in effluent into inorganic substance such as methane, carbon dioxide, hydrogen sulphide and water.

Another object of the present invention is to characterise the samples from various industries including viscose manufacturing industries, chemical industries and dye manufacturing industries. The present invention relates to Sample VI, Sample V2, Sample V3 and Sample V4, wherein, the Sample VI has a pH of 1.75, sulphate concentration of 26,601 mg per litre, sulphide concentration of 70 mg per litre and zinc concentration of about 370 mg per litre. Moreover, Sample V3 has a neutral pH of 7.71, sulphate concentration is 17,363 mg per litre and sulphide concentration 71.2 mg per litre and zinc concentration of about 38 mg per litre. Also, Sample V4 consists of an alkaline pH of 11.28 and sulphate concentration of about 95 mg per litre. According to certain embodiments the sample Cl obtained from the chemical industries wherein the pH of sample Cl is 5.52. Moreover, sample D1 obtained from dye making industries where the pH of sample D1 is 6.0.

According to one of the aspect the present invention provides a process of treatment of industrial effluent comprising of heavy metals as sulphates, arsenic, cadmium, chromium, copper, lead, nickel and zinc using anaerobic granulated biomass comprising the contacting of the wastewater containing water soluble sulphate ions and ionic heavy metal species with the Anaerobic Microorganisms consortia contained on the porous matrix is carried out under anaerobic conditions and in the presence of nutrients and at temperatures capable of providing for continued growth and steady state population densities of the bacteria.

According to another aspect the present invention relates to an Anaerobic treatment in Lab Scale Upflow Anaerobic Sludge Blanket Reactor for a significant reduction of COD, BOD and various heavy metals present in the effluent produced from viscose fibre manufacturing industries.

According to another aspect the present invention relates to a method for the treatment of industrial effluents which includes significant reduction in the amount of sulphur, heavy metals and COD from the sulphur rich viscose fibre manufacturing industrial effluents.

The foregoing aspects of the invention are illustrative of those that can be achieved by the present invention and are not intended to be exhaustive or limiting of the possible advantages which can be realized. Thus, these and other aspects of the invention will be apparent from the description herein or can be learned from practicing the invention, both as embodied herein or as modified in view of any variation which may be apparent to those skilled in the art.

BRIEF DESCRIPTION OF DRAWINGS The accompanying drawings illustrate the preferred embodiments of the invention and together with the following detailed description serves to explain the principles of the invention. Figure 1: Illustrates the combined treatment method for the effluent.

DETAILED DESCRIPTION OF THE INVENTION

To promote an understanding of the principles of the invention, reference will be made to the embodiment and specific language will be used to describe the same.

“Anaerobic Microorganisms” are the organisms that do not require oxygen for growth. They react negatively or even die in the presence of oxygen.

The term“microbial consortium” refers to, two or more microbial groups living symbiotically.

“Chemical oxygen Demand” is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. COD test quantifies the number of organics present in water.

“Total dissolved solids (TDS)” is a measure of the dissolved combined contents of all organic and inorganic substances that are present in a liquid in a molecular, ionized, or micro-granular suspended form. The term“effluent” means liquid waste or the sewage that is disposed into surrounding aquatic bodies.

The term“Bioremediation” is the use of living microorganisms to degrade the environmental contaminants into less toxic forms. It uses naturally occurring bacteria and fungi or plants to degrade or detoxify substances hazardous to human health or the environment. In the present invention“VSF” refers to viscose fibre manufacturing industries in which viscose refers to a type of rayon fibre that is made from natural sources such as wood and agriculture products that are regenerated as cellulose fibres.

Moreover, in the present invention“TSS” refers to Total Suspended Solids that is the dry-weight of suspended particles, that are not dissolved, in a sample of water that can be trapped by a filter that is analysed using a filtration apparatus. Also, “VSS” that stands for volatile suspended solids is a water quality measure obtained from the loss on ignition of the mass of measured total suspended solids.

In the present invention,“VFA” stands for volatile fatty acids are important elements in controlling the anaerobic digestion process and assessing the effectiveness of the digestion process within a wastewater treatment plant.

In the present invention the abbreviation“ALK” refers to alkalinity which is the ability of a liquid or substance to resist a change in pH, or the capacity of water to buffer against an acid.

The term,“Hydraulic Retention Time (HRT)” refers to a measure of the average length of time that a soluble compound remains in a constructed bioreactor. HRT affects the contact between substrates and microorganisms which also favours towards higher treatment efficiency.

The present invention relates to the process for the treatment of industrial effluent containing higher amount of Sulphur and heavy metals such as zinc, cobalt, arsenic, cadmium, chromium, copper, lead and nickel using a biological treatment of bioremediation. Anaerobic/ Aerobic digestion using granulated biomass of bacteria reduces the total dissolved solids in effluent and further decreases the amount of heavy metal pollutants such as sulphur and zinc from the effluent obtained from the industries. One of the embodiments of present invention is to reduce or eliminate the limitations in term of application, effectives, dumping of hazardous sludge on the landfill sites and cost of the conventional treatments of the industrial effluents.

One of the embodiments of the present invention is directed to a method of treating heavy concentrations of sulphate and zinc containing industrial effluent or water in a bioreactor comprising the steps of: (a) inoculating the consortium of sulphur-reducing bacteria in the 20L Lab-scale Aeration Tanks; (b) introducing fresh media into the aeration tanks for the survival of the bacteria; (c) introducing the solution comprising the sulphate and zinc pollutants containing effluent or water; (d) reducing the sulphate in the effluent biologically to sulphide;

Wherein the aeration tank was capable for reducing 49-50% of the sulphate concentration from the industrial effluent within 6 hours only.

The present invention is further directed to Anaerobic Treatment in lab scale UASB bioreactor for treating sulphate containing effluent or water, comprising of UASB reactor wherein, no support material is used in with combination of bacterial anaerobes. Industrial effluent in introduced from the bottom portion of the anaerobic reactor, flows upwards and is discharged through the upper portion of the reactor. The industrial effluent is introduced in the reactor and the pollutants sulphate, sulphide, zinc is removed by the means of anaerobic granulated biomass. The Anaerobic Treatment is capable for reducing 93% of sulphur and 99% of zinc content from the effluent.

According to one of the embodiments the present invention provides an apparatus for the treatment of industrial effluent containing high concentrations of sulphur and zinc. Moreover, the industrial effluent also comprises of high concentration of suspended solids. The combined treatment method for the effluent as shown in Figure 1 comprises of the following steps: a) Industrial effluent containing higher concentration of sulphate and Zinc is introduced in the Feed tank (1).

b) From the feed tank (1) the effluent fluid stream is introduced to UASB reactor (3) using first peristaltic pump (2). In the Figure 1 the peristaltic pump is denoted by (2).

c) Once, the effluent reaches the UASB reactor (3), the effluent goes through internal recirculation using second peristaltic pump (4). The second peristaltic pump is denoted (4) in Figure 1. The Anaerobic treatment is carried out in the UASB reactor.

d) Once the recirculation of the effluent starts in the UASB reactor the complete conversion of the polluting components presents in the effluent into inorganic substances such as Methane, Carbon dioxide and Hydrogen sulphide. Also Zinc concentration is significantly reduced in this step. The gas is collected by water displacement method in gas holder on the top of UASB reactor. From the gas collector the gas is displaced out from Biogas Outlet (5).

e) And finally, from the UASB reactor (3) the treated effluent is collected in anaerobically treated water tank denoted as (6) in Figure 1.

f) From the anaerobically treated water tank (6) the effluent water is sent to Aeration unit (7).

g) In this aeration unit (7) further reduction of Sulphate happens by significant percentage and aeration treated water (8) is recovered for its secondary and tertiary treatment and re-use.

According to one of the embodiments of the present invention the combination of Aerobic and Anaerobic treatability causes of about 90-99% significant reduction in the amount sulphur and zinc. To make the objectives, technical solutions and advantages of the present invention it will become more apparent hereinafter in conjunction with embodiments of the present invention will be further described in detail. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention.

EXAMPLES

The following examples are for illustrative purposes only and are not intended to limit the scope of the embodiments disclosed herein.

Example 1: Characterization of the effluent

Following samples of wastewater were collected from, VSF manufacturing industries:

Sample VI -Sample VI contains high amount of aqueous zinc chloride making Sample VI an acidic solution having significant COD levels.

Sample V2 - Sample V2 contains high amounts of zinc as it receives zinc directly from the outlet of a zinc clarifier.

Sample V3 - Contains a mixture of all streams

Sample V4 - Contains alkali hence has high pH and COD

The details of the Samples from VSF manufacturing industries are depicted in

TABLE la.

The present invention also relates with the sample characterization of wastewater collected from, chemical industry. In certain embodiments the samples obtained from chemical industries are depicted as Sample Cl. The details of the Samples from Chemical industries are depicted in TABLE lb.

Further, the present invention also relates to sample characterization of wastewater collected from, dye industry. In particular embodiments the samples obtained from dye industries are depicted as Sample Dl. The details of the Samples from Dye industries are depicted in TABLE lc. Example la: Effluent Characterization Study

The present invention relates to a kind of sustainable and effective methods for the wastewater generated during the production of viscose fibres, chemical industry and dye manufacturing industries, it also helps in identifying strategic interventions that can be used and applied to define a treatment strategy that addresses the sustainability issues associated with ETP (Effluent treatment Plant) Management.

The present invention relates to the effluent characterization obtained from various industries like viscose fibre manufacturing industries, chemical industries and dye manufacturing industries.

The characterization study was done to obtain controlled parameters, that included the pH, TDS, Conductivity, COD, BOD, TSS, VSS, VFA, ALK, sulphate, sulphide and zinc concentrations results of which are tabulated in Table la. The present invention relates to characterization of the effluent from viscose fibre manufacturing industries, chemical industries and dye making industries.

The characterization results evidently showed that though Sample VI had significant COD levels, still its direct treatment under biological pathway was not feasible and efficient due its very low pH around 1.75 in comparison with other samples. Moreover, the Sample V2 being an outlet from Zn removal clarifier and is an intermediate stream hence its direct treatment was not required. Sample V3 was obtained by mixing lime treated stream and rest of the waste water streams and has neutral pH. Moreover, Sample V4 had high pH of 11.28 making the Sample V4 highly alkaline.

In certain embodiments, first part of the study was focused on establishing an optimal treatment of Sample V3 by using innovative developed biomass. Table la: Sample Characterization Report from Viscose Fibre Manufacturing Industry

Table lb: Sample Characterization Report from Chemical Industry

Table lc: Sample Characterization Report from Dye Manufacturing

Industry

NF- Not Feasible, BDL - Below Detection Limit, NR - Not Required

Further on, the focus of the present invention is on treatment of Sample VI through biological means to significantly reduce amount of chemical sludge generated as a by-product of the wastewater treatment. The Sample VI being acidic and Sample V4 being alkaline waste streams constitute the bulk of the waste water and its pollution load from the viscose fibre manufacturing plant. The present invention relates to experiments that were performed for treating Sample VI after neutralization with Sample V4, maintaining the pH in the neutral range of 7-7.5, resulting in survival of the bacteria in the effluent. Hence it was decided to make composite sample of these two streams and checked its treatment with both aerobic and anaerobic biomass.

Example 2: Preparation of Granulated Biomass

The present invention relates to preparation of Anaerobic Granulated Biomass wherein, the preparation method comprises of:

a) Introducing various feed media into different reactors containing an active biomass sludge with VSS content of 600-700 mg/1.

b) Use of simple sugars in the feed medium and a source of nitrogen, phosphate and trace elements.

c) Providing mixing action to the seed sludge with the media at a pre -determined temperature of 40°C and 80 rotation per min. d) Allowing formed micro anaerobic granules/seed sludge to settle for 9-24-day incubation.

e) Transferring of seed sludge as produced in d) into UASB anaerobic reactor of cylindrical configuration and that operates in an anaerobic state.

f) Pure media or carbohydrate rich industrial effluent is introduced from the bottom portion of the anaerobic reactor; flows upwards through the seed sludge bed and is discharged through the upper portion of the anaerobic reactor.

g) At least a part of discharged of f) is re-circulated at a pre-determined temperature of 22-40°C and an organic loading rate of 2.5 -16.2 kg COD/m3. d; and pH between 4.0 and 9.0; alkalinity of the reactor in the range of 750- 1500mg/l.

h) Organic matter present in the pure media or waste water is removed by means of anaerobic treatment and granules are produced and simultaneously biogas such as methane is also produced.

i) Repeating steps (f), (g), and (h), for 90 - 120 days until the seed sludge develops into large Anaerobic Granules.

Example 3: Preparation of Composite Sample The present invention relates to preparation of Composite Samples that is the combination of Sample VI and Sample V4. The pH of Sample VI being acidic and had to be neutralized with a base in order to achieve appropriate pH for the survival of the bacteria present in the consortium, by treating Sample VI with Sample V4 of Hemicellulose having highly basic pH and high levels of COD. Treatment of Sample VI and Sample V4 neutralized the sample stream by setting up the pH at 7.0, that resulted in precipitation of pollutants but no settling of it. Hence pH was further increased till pH 7.7 which resulted in settling down of precipitates very fast. After this stage, the supernatant of the composite samples was taken and mixed with grit stream and was then treated aerobically and results obtained are listed in Table 3. Example 4: Biological Treatments The present invention relates to the removal of organic soluble impurities being an important stage. Under controlled conditions the biomass produced in the biodegradation process reduces the concentration of the biodegradable organic pollutants, resulting in reduction in COD, BOD and other pollutants like inorganic constituents (TDS) and heavy metals.

Example 4a: Aerobic Treatability

Aeration experiments were carried out in 20L Lab-scale Aeration Tanks containing Aerobic Biomass.

To test Aerobic Biomass efficiency a very low load of Sample VI was fed to aerobic tanks and 70 - 75% COD reduction was achieved. Also Sample V3 was tested with a low load and 84 - 88% COD reduction was achieved. Further, a full trial was done with Sample V3, the results of which is shown Table 2. It can be seen that along with COD & BOD reduction, there was more than 96% reduction in Zinc concentration as well. Also, it can be seen that innovative biomass was able to reduce Sulphate concentration in the sample.

Table 2: Results of Aeration Batch Process - Sample V3

Similarly, the composite sample prepared by the process mentioned above and was further treated in batch process. Table 3 provides the result for the Aeration Batch Process for the composite mixture.

Table 3: Results of Aeration Batch Process - Composite Sample (Sample VI

+ Sample V4)

Thus, in the present invention Sample V3 and Composite Samples both were treated with aerobic microbial granulated biomass for different retention time. The results obtained showed that although the composite sample had 3 times more COD as that of Sample V3, but then also only 67% and 87% COD reduction was achieved in 6 hours and 24 hours respectively. Also, 94% reduction in zinc concentration was observed after 24 hours. Thus, it can be concluded that higher the retention time will give better results for the treatment of sulphur and zinc.

Example 4b: Secondary/ Biological Treatment of Dye effluent

According to the present invention removal of organic soluble impurities is an important treatment stage, under controlled conditions; the biomass produced in the biodegradation process shall reduce the concentration of the biodegradable organic pollutant, resulting in reduction of BOD & COD values.

Aeration/ Aerobic experiments were carried out using Soil sample as well as with Halophiles from isolates as seed in 500 ml capacity round bottom flask. Air (oxygen) was provided by incubating flasks on shaker at 40°C. Grabbed samples were collected from the flasks after completion of designated HRT (Hydraulic Retention Time) and analysed for COD and pH as control parameter. The results for the Aeration Batch Process of the Soil Sample are given in Table 4.

Table 4: Analysis Results of Aeration Batch Process - Flask I Soil sample

Final Sulphate concentration of the effluent is about 26600 mg per litre.

Table 5: Analysis Results of Aeration Batch Process - Flask 2 Halophiles

Final Sulphate concentration of the effluent is about 17360 mg per litre.

The results of the secondary biological process by aerobic culture had indicated reduction in both COD and TDS for VSF manufacturing as well as Dye making Industries.

According to certain embodiments of the present invention after the Aerobic treatment the effluent was further carried for Anaerobic Biodegradability Test. The following example represents Anaerobic biodegradability Test of D1 Effluent.

Example 5: Anaerobic Biodegradabilitv Test of D1 Effluent The Anaerobic Biodegradability test is performed to confirm biodegradation of the chemicals present in effluent when subjected to an anaerobic wastewater treatment plants (WTP) or effluent treatment Plant (ETP). In the determination of the biodegradability a distinction is made between the degradability of effluent and toxicity to the sludge. The ultimate degradation is the complete conversion of the chemical components present in effluent into inorganic substances such as Methane, Carbon dioxide, H2S and water. According to one of the embodiments of the present invention, during two weeks of incubation, the sludge produced 4.5 ml gas / ml effluent treated, added which was burning hence indicating good concentration of CH₄ (Methane) content while H₂S gas content was only approximately 100 ppm (Parts Per Millions). With effluent used as feed, the sludge showed a COD reduction of 72% and VFA reduction by 85% while alkalinity of the treated effluent increased. The results are shown in Table 4.

Table 6: D1 effluent sample anaerobic biodegradability analysis report

The Final Sulphate concentration was about 23000 mg per litre.

The present invention provides with the anaerobic treatment results, indicating suitability of biological process as part of the treatment scheme. Thus, the present invention relates to a method of treatment of industrial effluent with combination of anaerobic granulated bacterial consortium and aerobic bioreactors.

Moreover, the present invention provides with results that shows under limited period of lab experimentation that results with the provided effluent indicates that effluent is not toxic but sludge needs time to adapt to solubilize complex effluent COD to methane Example 6: Anaerobic Treatment in Lab-Scale UASB reactor

According to one of the embodiments the lab scale UASB reactor study was conducted in 10 L reactor containing Anaerobic Granulated Sludge. As mentioned above, Anaerobic Biodegradability Test of Sample V3 showed COD reduction and formation of methane gas which made it suitable for feeding it to UASB reactor. The results are indicated in Table 7. Anaerobic Treatment in Lab Scale UASB reactor showed gas production of 630 ml/litre of the sample fed. Average COD reduction showed in this particular embodiment was about 91% while BOD reduction of about 77% was achieved. The results also indicated a significant reduction in Zinc, Sulphate and Sulphide concentration.

Table 7: Results of Anaerobic Lab-scale UASB Process - Sample V3

According to the above-mentioned embodiments, Composite Sample which is a mixture of Sample VI and Sample V4 was treated with Anaerobic Treatment in Lab Scale UASB reactor. The results obtained for Composite Sample are illustrated in Table 8. The present results indicated gas production of 702 ml per litre of the sample fed. The results showed a significant reduction of COD by 77% and also significant reduction in the concentrations of Zinc and Sulphur.

Table 8: Results of Anaerobic Lab-scale UASB Process - Composite Sample

The present invention provides an efficient and faster method of reduction of soluble sulphate from the industrial effluent obtained from various industries using a combination of aerobic and anaerobic treatment using granulated biomass. The present invention provides a method of treatment of contaminated water that functions under ambient temperature.

The present invention provides a method of reducing high concentrations of sulphate, zinc and along with reduction of biological oxygen demand and chemical oxygen demand.

The present invention provides a highly efficient, plant scale method that is an alternative to an expensive physicochemical approach or a less efficient biological approach. The present invention relates to use of innovative aerobic and anaerobic granulated biomass can be used to treat organic content of effluent having high sulphate and zinc concentrations.

5 Thus, treatment of effluent having high TDS especially sulphates by combining Anaerobic and Aerobic Technology will be an economical and sustainable way of treatment as compared to the current effluent treatment process based on chemical treatment followed by aeration as treatment plants will generate less amount of sludge as well as less electricity hence operational cost will be reduced by 60- 0 70%.

Table 9: Comparison table for Aerobic treatment, Anaerobic treatment, and a combination of Aerobic and Anaerobic treatment

The above Table 9 shows the results of the present invention, wherein, the combined aerobic and anaerobic treatment shows 98-99% removal of sulphate and sulphide. Moreover, the zinc concentration reduces significantly after the anaerobic treatment.

Claims

CLAIMS: We claim;

[CLAIM 1] A method of removing heavy metal from industrial effluents by combination of aerobic and anaerobic treatment comprising steps off: a) characterization of the effluent for maintaining pH in the range of 6 to 7.5;

b) treating the effluent in aerobic reactors for retention period of 6 to 24 hours;

c) further, treating the effluent with anaerobic granulated biomass at a temperature range of 22-40°C, wherein the biomass comprises of sulphur reducing and methanogenic bacteria.

[CLAIM 2] The method as claimed in claim 1, wherein the effluent is from viscose manufacturing industries, inorganic chemical industries and dye manufacturing industries.

[CLAIM 3] The method as claimed in claim 1, wherein the anaerobic granulated biomass comprises of 32-35% is methanogenic bacteria and 65-68% of sulphur-reducing bacteria.

[CLAIM 4] The method as claimed in claim 1, wherein the preparation of anaerobic granulated biomass comprises of:

a) introducing various feed media into different reactors containing an active biomass sludge with VSS content of 600-700 mg/1;

b) use of simple sugars in the feed medium and a source of nitrogen, phosphate and trace elements;

c) providing mixing action to the seed sludge with the media at a pre-determined temperature of 40°C and 80 rotation per min; d) allowing formed micro anaerobic granules/seed sludge to settle for 9-24-day incubation;

e) transferring of seed sludge as produced in d) into UASB anaerobic reactor of cylindrical configuration and that operates in an anaerobic state;

f) pure media or carbohydrate rich industrial effluent is introduced from the bottom portion of the anaerobic reactor; flows upwards through the seed sludge bed and is discharged through the upper portion of the anaerobic reactor;

g) discharged of f) is re -circulated at a pre-determined temperature of 22-40°C and an organic loading rate of 2.5 -16.2 kg COD/m3. d; and pH between 4.0 and 9.0; alkalinity of the reactor in the range of 750-1500mg/l;

h) organic matter present in the pure media or waste water is removed by means of anaerobic treatment and granules are produced and simultaneously biogas such as methane is also produced;

[CLAIM 5] The method of treating sulphate and zinc containing effluent as claimed in claim 1, wherein the effluent is treated aerobically in 20 Litre Aeration Bioreactors.

[CLAIM 6] The Aerobic method of treating sulphate and zinc containing effluent as claimed in claim 3, wherein the aerobic bioreactor reduces 49-50 % of sulphate concentration from the effluent.

[CLAIM 7] The method of treating sulphate and zinc containing effluent as claimed in claim 1, wherein the effluent is treated anaerobically with anaerobic granulated biomass.

[CLAIM 8] The anaerobic method of treating the effluent as claimed in claim

4, reduces 93% of sulphur and zinc from the industrial effluent.

[CLAIM 9] The method of treating sulphate and zinc containing effluent as claimed in claim 1, wherein the combined aerobic and anaerobic treatment reduces 98-99% of sulphate concentration from the effluent.

[CLAIM 10] The method of claim 1, wherein the sulphur reducing bacteria comprises of species of genera Acidianus convivator, Caldisphaera draconis, Halogeometricum rufum, Halorubrum cibi, Natronococcus occultus, Pyrococcus yayanosii, Vulcanisaeta moutnovskia, Desulfobulbus, Desulfobacter, Desulfovibrio, Desulfurmusa, Thermodesulfobacteria, Archaeo globus.

[CLAIM 11] The method of claim 1, wherein the methanogenic bacteria comprises of species of genera Methanobacterium curvum, Methanobacterium congolense, Methanobacterium kanagiense, Methanobacterium beijingense, Methanobacterium formicicum, Methanobacterium uliginosum, Methanobacterium aarhusense, Methanobacterium bryantii, Methanobacterium subterraneum, Methanobacterium palustre, Methanobacterium oryzae, Methanobrevibacter acididurans, Methanobrevibacter ruminantium, Methanobrevibacter gottschalkii,

Methanobrevibacter curvatus, Methanobrevibacter smithii, Methanocalculus taiwanensis, Methanocella paludicola, Methanococcoides methylutens, Methanoculleus receptaculi, Methanofollis ethanolicus, Methanolobus psychrophilus, Methanomethylovorans thermophila, Methanomethylovorans hollandica, Methanosaeta concilii, Methanosaeta pelagica, Methanosaeta harundinacea, Methanosaeta thermophila, Methanosarcina baltica, Methanosarcina barkeri, Methanosarcina siciliae, Methanosarcina vacuolate, Methanosarcina mazei, Methanosarcina acetivorans, Methanosphaera stadtmanae, Methanosphaera cuniculi, Methano spirillum hungatei.

[CLAIM 12] The method of claim 1, wherein the reactor is Upflow Anaerobic

Sludge Blanket reactor that can retain the granulated biomass by virtue of the good settleability of biomass and the design of special separators internal to the reactors that can effectively separate and retain such granular biomass often referred to as granular sludge.

[CLAIM 13] A bioreactor system for treating sulphate and zinc containing industrial effluent comprising following steps:

(a) Industrial effluent containing higher concentration of sulphate is introduced in the Feed tank;

(b) From the feed tank the effluent fluid stream is introduced to Upflow Anaerobic Sludge Blanket reactor;

(c) the effluent that reached the Upflow Anaerobic Sludge Blanket reactor goes through internal recirculation;

(d) the Anaerobic treatment is carried out in the Upflow Anaerobic Sludge Blanket reactor;

(e) the reduction of pollutants cause production of gases such as Methane, Carbon dioxide and Hydrogen sulphide; (f) the treated effluent is collected and stored in treated water tank.