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Title:
METHOD AND APPARATUS FOR ZERO DISCHARGE TREATMENT OF INDUSTRIAL WASTEWATER STREAMS
Document Type and Number:
WIPO Patent Application WO/2017/072787
Kind Code:
A1
Abstract:
Disclosed is a method and apparatus for the treatment of industrial wastewater stream leading to zero discharge of waste matter. The method and apparatus is used for treatment of wastewater such as distillery spent wash which may be raw or molasses spent wash or bio-methanated spent wash. The stages include one or more of evaporation, chemical adsorbent treatment, solid-liquid separation, concentration and binder treatment. The method particularly relates to the reduction of viscosity building substances from said wastewater streams and further concentration of such viscosity building substance removed stream so that about 80 to 90% water is recovered from said wastewater streams. The method further provides solid by-products that may be used as fuel and soil conditioner components.

Inventors:
DESHPANDE, Ghansham Baburao (PRAJ Tower, 274-275Bhumkar Chowk -Hinjewadi Road,Hinjewadi, Pune 7, 411057, IN)
KADU, Bharat Ashok (PRAJ Tower, 274-275Bhumkar Chowk -Hinjewadi Road,Hinjewadi, Pune 7, 411057, IN)
KULKARNI, Ravindra Laxman (PRAJ Tower, 274-275Bhumkar Chowk -Hinjewadi Road,Hinjewadi, Pune 7, 411057, IN)
PATIL, Nitin Sudhakar (PRAJ Tower, 274-275Bhumkar Chowk -Hinjewadi Road,Hinjewadi, Pune 7, 411057, IN)
SAWANT, Jayant Shridhar (PRAJ Tower, 274-275Bhumkar Chowk -Hinjewadi Road,Hinjewadi, Pune 7, 411057, IN)
Application Number:
IN2016/050339
Publication Date:
May 04, 2017
Filing Date:
October 07, 2016
Export Citation:
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Assignee:
PRAJ INDUSTRIES LIMITED (PRAJ Tower, 274-275Bhumkar Chowk -Hinjewadi Road,Hinjewadi, Pune 7, 411057, IN)
International Classes:
C05F5/00; C02F9/00; C02F11/00; C05F7/00; F26B7/00
Foreign References:
US4193206A1980-03-18
US4808287A1989-02-28
Attorney, Agent or Firm:
KINGE, Parag (A-104, Royal Twins Near Devideep Society,Nda-Pashan Road, Pune 1, 411021, IN)
Download PDF:
Claims:
CLAIMS

WE CLAIM:

1 . A method for the treatment of a wastewater stream comprising:

(a) subjecting said wastewater stream to evaporation forming a concentrated stream and a condensate stream;

(b) treating said concentrated stream with an insoluble activator leading to the capture of viscosity causing substances forming a treated stream;

(c) subjecting said treated stream to solid-liquid separation forming a liquid stream and a fuel cake;

(d) subjecting said liquid stream to concentration forming a high- solids stream and a second condensate stream; and

(e) treating said high-solids stream with an insoluble binder forming solid stream.

2. The method of claim 1 , wherein said wastewater stream comprises vinasse or raw spent wash or biomethanated spent wash or industrial wastewater or municipal wastewater.

3. The method of claim 1 , wherein said wastewater stream comprises viscosity building substances like dead cellular matters or proteins or lipids or nucleic acids.

4. The method of claim 1 , wherein said wastewater stream comprises total solids up to 15% by weight.

5. The method of claim 1 , wherein said wastewater stream is evaporated using a multiple-effect evaporator or a mechanical vapour recompressor or a reverse osmosis method.

6. The method of claim 1 , wherein said concentrated stream comprises total solids up to 30% by weight.

7. The method of claim 1 , wherein said insoluble activator comprises activated carbon or charcoal or bio-charcoal...

8. The method of claim 1 , wherein said insoluble activator is having a surface area of between about 300 m2/g to about 500 m2/g.

9. The method of claim 1 , wherein said insoluble activator is having adsorption surface area of between about 80 mg to about 120 mg of

285 methylene blue dye per gram of said activator.

10. The method of claim 1 , wherein said solid-liquid separation of said treated stream is achieved by a physical separation technique like filtration or centrifugation.

1 1 . The method of claim 1 , wherein said concentration of said semi-solid 290 stream is achieved by evaporation.

12. The method of claim 1 , wherein said insoluble binder comprises a fibrous biomass-based substance like bagasse or agricultural solid waste or wood waste or a press mud.

13. The method of claim 1 wherein the said insoluble binder is boiler 295 ash.

14. The method of claim 1 , wherein said condensate stream and said second condensate stream are recycled as process water.

15. The method of claim 1 , wherein recovery of water from said wastewater stream is at least 80% by weight.

300 16. The method of claim 1 , wherein said fuel cake comprises ash not more than 20% by weight.

17. The method of claim 1 , wherein said fuel cake having calorific value of at least 2000 kcal/kg.

18. The method of claim 1 , wherein said solid stream is suitable for use 305 as a soil conditioner or a fertilizer component.

19. The method of claim 1 , wherein said solid stream has potassium content of at least 5% by weight.

20. A fuel cake according to claim 1 is used as a fuel substance or a solid fuel additive.

310 21 . A solid stream according to claim 1 comprising organic matters at least 50% by weight, ash at least 15% by weight and potassium as potassium oxide at least 5% by weight.

22. A system for the treatment of wastewater stream comprising:

315 (i) a collection unit for storage of said wastewater stream;

(ii) an evaporation unit to concentrate said wastewater stream forming a concentrated stream and condensate stream;

(iii) an activator treatment unit to treat said concentrated stream with an activator forming a treated stream;

320 (iv) a solid-liquid separation unit to separate said treated stream to a fuel cake and a liquid stream;

(v) a concentration unit to concentrate said liquid stream to a high-solids stream and second condensate stream; and

(vi) a binder treatment unit to treat said high-solids stream 325 with a binder forming a solid stream.

23. The system of claim 22, wherein said evaporation unit is a multiple- effect evaporator or a mechanical vapour recompressor or a reverse osmosis unit.

24. The system of claim 22, wherein said activator treatment unit is a 330 mixer that optimally incorporates said activator.

25. The system of claim 22, wherein said solid-liquid separation unit is a filtration unit or a centrifuge unit.

26. The system of claim 22, wherein said concentrator unit is a filtration unit or a centrifuge unit.

335 27. The system of claim 22, wherein said binder treatment unit is a mixer that optimally incorporates said binder.

28. The system of claim 22, wherein said treatment is a continuous process with said units operating in a series.

Description:
TITLE

METHOD AND APPARATUS FOR ZERO DISCHARGE TREATMENT OF INDUSTRIAL WASTEWATER STREAMS. FIELD OF THE INVENTION

Disclosed is a method and apparatus for the treatment of industrial wastewater stream leading to zero discharge of waste matter. The method and apparatus is used for treatment of wastewater such as distillery spent wash which may be raw or molasses spent wash or bio-methanated spent wash. The stages include one or more of evaporation, chemical adsorbent treatment, solid-liquid separation, concentration and binder treatment. The method particularly relates to the reduction of viscosity building substances from said wastewater streams and further concentration of such viscosity building substance removed stream so that about 80 to 90% water is recovered from said wastewater streams. The method further provides solid by-products that may be used as fuel and soil conditioner components.

BACKGROUND

An ethanol distillery produces about 10 litres of spent wash [SW] for every litre of alcohol produced. The spent wash typically has a high chemical oxygen demand [COD], for example, 80 g/L or more. It further contains toxic pollutants, hardness and suspended impurities causing turbidity. As a result the spent wash cannot be safely discharged into the environment. When molasses is used as a raw material in the distillery; then the raw or molasses spent wash [RSW or MSW] is dark brown in colour, and when disposed off in open fields it is extremely polluting.

In India between 30 - 40 billion litres of spent wash is produced from about 250 to 400 distilleries per year. These distilleries typically use molasses as a raw material. Anaerobic digestion is one treatment method used by distilleries to treat the spent wash since it produces a biogas that may be used to provide heat or power to the distillery. The digester also produces an effluent called bio-methanated spent wash [BSW], which further has the COD, suspended solids and dissolved solids of the effluent still too high and it is highly polluting and cannot be discharged as such.

Raw spend wash [RSW] is made up of matter left unused after distillation process; this matter is mostly in the form of biomass, organic and inorganic complexes having very high BOD and COD demands for its degradation in natural environment thus creating pollution on discharge. The compositional analysis of a typical RSW sample is provided in TABLE 1 .

TABLE 1 : TYPICAL COMPOSITION OF A RSW FEED STREAM.

BSW is made up of matter left unused in bio-methanation [digestion] process and produced during metabolism; this matter is mostly in the form of biomass, organic and inorganic complexes having very high BOD and COD demands for its degradation in natural environment creating pollution everywhere. The compositional analysis of a typical sample of BSW is provided in TABLE 2.

TABLE 2: TYPICAL COMPOSITION OF A BSW FEED STREAM.

Presently, RSW or BSW is left in open fields to decompose and then remains are used as fertilizer, etc. At some large factories it is evaporated to partially recover water that is disposed off in natural streams and the concentrated part is left for composting or is incinerated In recent times there has been a significant pressure on sugar factories to reduce water consumption and recycle the process wastewater generated in plants more effectively. To this end, several technologies have been presented for the treatment of BSW and recovery / recycle of process wastewater. However, these technologies have limitations in terms of the composition of recycled water obtained, which is not suitable for fermentation which is the most water consuming step, during making of alcohol.

Many processes have been used to treat the distillery effluents. An evaporation approach although widely practised has severe limitations in terms of operating costs especially maintenance due to corrosion and scaling problems. Further, limitation of evaporation is that the SW can only be concentrated up to maximum 60% solids. At this stage it becomes very sticky and highly viscous in nature. This concentrated SW is then difficult to handle and dispose. Other techniques like filtration followed by RO and treatments with fungus or other micro-organisms have also failed. Therefore at present, there is need of a low cost, high recovery, reliable and eco-friendly technology for the treatment of distillery spent wash. The invention disclosed herein relates to wastewater treatment, treatment of 80 effluents from anaerobic/ aerobic digesters and treatment of distillery spent wash, for example molasses/ raw spent wash.

The invention presented herein discloses a method and apparatus for the treatment of industrial wastewater streams having several advantages over 85 known methods. Besides it provides recycled water at the end of treatment that is usable in plant processes like in the fermentation of sugars by yeast. Further the solid by-products obtained are also used as fuel and soil conditioner components.

90 BRIEF DESCRIPTION OF THE DRAWINGS

Particular examples of a method and apparatus in accordance with this invention will now be described with reference to accompanying drawings, in which:

95 FIGURE 1 is a schematic process flow diagram of a wastewater treatment plant as per the method of the invention disclosed.

FIGURE 2 is a schematic apparatus diagram of a wastewater treatment plant as per the invention disclosed.

100 DETAILED DESCRIPTION OF THE INVENTION

In one embodiment of the present invention, as illustrated in FIGURE 1 , the five steps of the said method are: 1 ] evaporation of the feedstock [any of said wastewater streams] to concentrate it, 2] activator treatment of the

105 concentrated stream, 3] solid-liquid separation of treated stream, 4] concentration of liquid stream and 5] binder treatment of high-solids stream. In the first step, the said feedstock [effluent stream], having total solids up to 15% by weight, is evaporated by action of a multiple-effect evaporator or a mechanical vapour recompressor or a reverse osmosis

110 method to concentrate it to total solids up to 30% by weight forming a concentrated stream. In the second step, said concentrated stream is treated with an insoluble activator that substantially removes the viscosity building substances from the stream by adsorption and entrapment of the substances from said stream. In the third step, said insoluble activator with

115 adsorbed and entrapped substances is removed by virtue of solid-liquid separation by means of either centrifugation or filtration. The separated solid cake termed fuel cake is used as a fuel component as it has excellent solid fuel properties. In the forth step, the filtrate liquid stream is subjected to evaporation and concentrated up to 75% solids by weight forming a high-

120 solids stream. In the fifth step, said high-solids stream is treated with a binder forming a solid cake useful as a fertilizer component or a soil conditioner being rich in elements like potassium, nitrogen, etc. The condensate streams obtained in said two evaporation steps are used as recycled process water, without any discharge of liquid effluents from the 125 processing plants. This process affords about 80 to 90% recovery of water from said wastewater streams, while solids present in said wastewater streams form by-products used as solid fuel additive and soil fertilizer applications. There is zero discharge of waste liquid or solids from using the method of the invention disclosed herein.

130

In another embodiment of the present invention, said feedstock is one or more of vinasse or raw spent wash stream or biomethanated spent wash stream or industrial wastewater stream or municipal wastewater stream. It may as well comprise a wastewater stream containing high amounts of 135 biological matter that lead to forming of viscous mass on evaporation with at least 30% water remaining in it at the time of its disposal in landfills.

In yet another embodiment of the present invention, as illustrated in FIGURE 2, the five units of the said apparatus are: 1 ] an evaporator to

140 concentrate said wastewater stream [feedstock], 2] activator mixer for addition and mixing of said activator, 3] a centrifuge or filtration unit for solid-liquid separation of activator treated stream, 4] concentrator for concentrating said liquid stream and 5] binder mixer for treatment of high- solids stream with a binder. These units of said apparatus function in a

145 series causing the desired changes on said feedstock and subsequently generated streams leading to substantial removal of viscosity causing materials or biomolecules from said concentrated stream upon its treatment with said activator forming said a fuel cake and a liquid stream. Next, said liquid stream is then further concentrated in said concentrator forming a 150 high-solids stream, which is mixed with said binder forming a solid cake and a second condensate stream. The condensate streams from said evaporator and said concentrator are further used as recycled process water.

In yet another embodiment of the present invention, the insoluble activator 155 is a powdery carbon substance having adsorption surface area of between about 300 m 2 /g to about 500 m 2 /g on its microsporous structures. The said insoluble activator is made from carbon materials like charcoal or biochar or any other biomass or coal based stocks. Herein, the adsorbent surface area of the insoluble activator is measured using standard method of 160 determining methylene blue dye number known in the art. The activator used in the present invention has methylene blue number between about 80 to 120 mg methylene blue per gram of said activator.

In yet another embodiment of the present invention, the fuel cake formed 165 has composition as shown in TABLE 3.

TABLE 3: COMPOSITION OF THE FUEL CAKE. c 36.17 % w/w

H 2.14 % w/w

O 19.33 % w/w

N 2.32 % w/w

S 1 .1 % w/w

Ash 18.5 % w/w

170 In yet another embodiment of the present invention, the binder is a fibrous powdery dry biomass material made from bagasse, wood chips or wood waste or agricultural waste or pre mud from a sugar distillery. When mixed with said high-solids stream up to 80% by weight it for said solid cake that may be used as an agricultural adjuvant or a soil conditioner or fertilizer

175 component being rich in minerals as shown in TABLE 4.

TABLE 4: COMPOSITION OF THE SOLID CAKE.

In another embodiment of the present invention, effect of treatment of 180 activator on the viscosity of the concentrated wastewater stream containing about 30% solids by weight is shown in TABLE 5. The activator treatment at about 1 % by weight of solids present reduced the viscosity optimally such that after removal of settled solids after said activator treatment, remaining liquid stream can be concentrated more than 70% solids by 185 weight and it still remains flowable and easy to handle, while the untreated said wastewater stream becomes highly viscous at about 60% solids by weight forming a sticky mass.

TABLE 5: VISCOSITY PROPERTIES OF ACTIVATOR TREATED 190 CONCENTRATED WASTEWATER STREAMS.

EXAMPLE 1 About 870 kg of raw spent wash from a distillery containing about 10.7%

195 solids was evaporated at 70 Q C under reduced pressure of about 100 immHg. Here about 550 kg of condensate stream was recovered. The remaining 320 kg concentrated stream was treated with about 1 .67 kg of activator at 70 Q C under constant stirring for a period of about 30 minutes. After 30 minutes the treated stream was subjected to centrifugal separation

200 to obtain two streams, namely, about 34 kg of sludge called a fuel cake and about 288 kg of centrifuged stream having 19% solids called a liquid stream. The liquid stream was further evaporated to obtain about 90 kg of high -solids stream with about 60% solids by weight with a dynamic viscosity of about 320 cp at 50 Q C and about 198 kg a second condensate

205 stream. Said high solids stream was blended with 15 kg of powdered dry bagasse or biomass to obtain a solid stream called soil conditioner having composition as shown in TABLE 6. The fuel cake obtained was used as a solid fuel additive and its composition is depicted in TABLE 7. This method afforded about 86% water recovery from the feedstock RSW stream

210 without any discharge of solid or liquid waste streams.

TABLE 6: SOIL CONDITIONER - COMPOSITION

c % w/w 40.43

H % w/w 2.03

O % w/w 19.46

N [Total nitrogen] % w/w 2.71

S % w/w 1 .05

Ash % w/w 24.04

TABLE 7: SLUDGE [AS A FUEL CAKE] - COMPOSITION

215

EXAMPLE 2

The raw spent wash containing about 12.16% of solids by weight was treated with about 1 .2 % of activator by weight. The mixture was heated to about 70 Q C and stirred for 30 minutes at that temperature. Then it was

220 subjected to centrifugation to separate out solid sludge. Then the liquid stream was subjected to evaporation to get a concentrated stream with about 60% solids by weight. Then the dynamic viscosity of said concentrated stream was measured at 60 Q C at various shear rates. As a control the raw spent wash containing 12.16% was directly evaporated to

225 about 60% solids by weight without activator treatment. TABLE 8 shows the effect of activator treatment on the dynamic viscosity of treated and untreated raw spend wash. The activator treatment substantially reduced the viscosity of the treated stream affording further concentration of the stream to solid mass. Further about 1000 kg of bio-methanated spent wash

230 containing 5% solids was acidified to pH 4 and was added 10 gm of activator. The mixture was heated to about 70 Q C and stirred for 30 minutes at that temperature. Then the liquid stream was subjected to evaporation to get a concentrated stream with about 60% solids by weight. Then the dynamic viscosity of said concentrated stream was measured at 60 Q C at

235 various shear rates. As a control the bio-methanated spent wash containing 5.0% solids was directly evaporated to about 60% solids by weight without activator treatment. TABLE 3 shows the effect of activator treatment on the dynamic viscosity of treated and untreated bio-methanated spent wash. The activator treatment substantially reduced the viscosity of the treated

240 stream affording further concentration of the stream to solid mass.

TABLE 8: COMPARATIVE VISCOSITY DATA

Embodiments provided above give wider utility of the invention without any limitations as to the variations that may be appreciated by a person skilled in the art. A non-limiting summary of various embodiments is given in the examples and tables, which demonstrate the advantageous and novel aspects of the process disclosed herein.