INDUSTRIAL WASTE WATER RECYCLING – A TECHNO-COMMERCIAL PAPER – The Catalysts Group

INDUSTRIAL WASTE WATER RECYCLING – A TECHNO-COMMERCIAL PAPER

ABSTRACT

Environmental norms to achieve zero discharge in distilleries have become stringent, and distilleries have to operate a multi-effect evaporator system (MEE) for spent wash concentration to match incineration boilers and bio-composting norms. Evaporation/concentration of spent wash (vinasse) leads to the generation of clear condensate water. The presence of organic loading, low pH, and volatile acid however restrict the use of condensate for process dilution cooling tower makeup. Many condensate polishing units are installed in the industry, but none offer techno-economical solutions because of high operating costs. Catalysts has developed a new biological solution for treating the volatile acids caused stress during fermentation. The product named “Enzytreat Plus” helps to treat the process condensate by suppressing the broad-spectrum contaminants, which directly or indirectly contribute to the volatile acidity formation. Enzytreat Plus further helps  decrease the volatile acidity stress on yeast during fermentation, which helps to improve yeast growth rate & specific productivity.

INTRODUCTION 

Industrial wastewater treatment is the industrial-scale process that makes water more acceptable for end-use, such as drinking, recycling, irrigation, and/or discharging in natural water bodies. Wastewater treatment should either remove existing organics, heavy metals, and microbial contaminants from water or reduce their concentration so that the water becomes fit for its desired end-use, including safely returning used water to the environment.

The processes involved in water treatment for industrial purposes by self-generated wastewater are to provide a reusable source of water supply. These include solids separation using physical processes such as settling and filtration, microbiological degradation such as aerobic & anaerobic digestion, and chemical processes such as disinfection and coagulation.

In India, wastewater (effluent) management for ethanol production distilleries is a very difficult task due to strict norms that NGT (National Green Tribunal) has imposed on these industries for zero effluent discharge (ZLD). Maintaining this practice is not possible for most ethanol production industries. The waste (effluent) contributors of ethanol manufacturing industries  are spent wash and other streams like water used in washing/cleaning, pantry discharges, etc. Many of the ethanol industries are currently using conventional processes for effluent treatment and disposal, including bio-methanation, ferti-irrigation, reverse osmosis and bio-composting. These conventional treatment methods are not  efficient enough to achieve zero discharge. In efforts to achieve zero liquid discharge (ZLD), most industries are focusing on incineration and/or evaporator technology. This technology evaporates liquid and incinerates solids to achieve ZLD and has very difficult and time-consuming processes.

On the other hand, recycling of treated effluent within the process is also being attempted with use of technology, but due to high salt concentration and toxicity in effluent; it is difficult to recycle the spent wash (effluent) beyond a limit that may vary from none to 10/15 % depending on the nature & characteristics of effluent. This recycling technology will be the future best adaptable technology due to some inherent benefits such as;

  • Minimize the cost of effluent treatment
  • Reduce the cost of capital expenses (CAPEX)
  • Reducing the dependency & input cost for freshwater
  • Reducing effluent generation
  • Achieve ZLD
  • Create a better environment for nature
  • Energy & Manpower saving
  • Using Carbon credit, etc

As discussed earlier, complete recycling of effluent within the process is a difficult task. A maximum of 10 – 15 % recyclable quantity is achieved against the generation of total effluent.

Catalysts Biotechnologies Pvt Ltd. has been working as a pioneer in this direction for increasing the recyclable quantity to help ZLD and minimizing the treatment cost of effluent. It provides the best and environmentally safe solution to increase effluent recycling, which directly supports ZLD and makes lives better. A unique product by Catalysts Biotechnologies Pvt. Ltd., India, “Enzytreat Plus” is an enzyme, having Proteolytic activity, designed for usage in Molasses and Grain-based Distilleries.

On account of freshwater scarcity, industries prefer natural water resources like underground water, canal water, river water, etc., or recycled wastewater streams generated within the Distilleries. Recycling generated streams, i.e., spent lees, RO permeates, process condensate, and spent wash or thin slops, help meet ZLD but significantly reduce process yield due to high TDS and high microbial contamination levels. These streams have a significant level of salts & microflora, which are thriving in such conditions and fastidiously grow in pre-fermenter and fermenters, resulting from some hindrances in process, like; increased foaming during propagation & fermentation, high volatile acids formation, decreased yeast health & productivity, increases competition between yeast & contaminants, slime production, increase antifoam consumption, etc.

To control these micro-organisms to propagate in the process, Catalysts provide a unique solution, formulated as Enzytreat Plus.

MATERIALS & METHODS

Enzytreat Plus usage is recommended to be used at 20 – 25 ppm on process water and/or recycled stream volume when used in the storage tank of these streams. Enzytreat Plus should be used directly in the fermentation tank at 10 – 15 ppm, depending on the contamination level of volatile acidity. Recommendations for Enzytreat Plus, to facilitate increase the amount of recycled stream in fermenter; is to use continual increase of recycle stream addition from minimum to maximum by continuous Enzytreat Plus application within the same setup and with same currently running recycled quantity for 5 – 7 days; it will improve the quality of spent wash and other related streams. Subsequently, increase the amount of recycled steam by 5% of fermenter volume, stabilize for the next 3 – 4 fermentation cycles, and increase 5% by repeating the same exercise until the maximum recycle quantity is achieved without any efficiency loss. The principle behind recycling is;

Toxicity & Volatile acidity in spent wash    ∝        _____________1__________

% recycled stream quantity

 

Improvement in spent wash quality                      ∝           % recycled stream quantity

 

RESULTS AND DISCUSSION

The plant trial of the product Enzytreat Plus was conducted on waste streams recycled at various cane molasses-based ethanol fermentation industries, where Enzytreat Plus was used directly in the fermentation process. The results were analyzed by observing the parameters, i.e., % recycling of waste stream, reduction in volatile acidity, fermentation efficiency, % Alcohol, recovery, etc.

CASE STUDY IN INDIA

Enzytreat Plus was applied in Ambalika Sugar, a newly commissioned distillery, where the total wash generation is 1050 m3/day and spent wash after distillation was around 960 m3/day. Further, it was concentrated in an evaporator to 65 Brix and obtained 200 m3/day concentrated spent wash. It was then processed to be burnt in an incinerator cum boiler and obtained around 50 m3/day of condensate. Characteristics of this condensate were observed pH 2.8-3, VA 3500 – 4000 ppm, COD of 3500 ppm, and BOD of 2000 ppm.

Prior to Enzytreat Plus’s application, the industry was used to treating condensate by CPU (condensate polishing unit) before entering the cooling tower. The chemical treatment cost of operating CPU was around 25-30 Lacs/ month, and CPU could not treat condensate water to meet the treated water norms for process reuse even after incurring a high chemical cost and drained condensate.

Usage of ‘Enzytreat Plus’ enabled them to consume all the condensate in fermentation. They were using spent lees of around 125 m3 to balance the pH and other parameters of condensate in fermenters. Around 200 m3/ day of fresh water was used in Pre-Fermenters where the pH and VA were approximately 4.5 and 3000 respectively in the setup of fermenters. Now, this plant has been running continuously without any stoppage and achieving zero liquid discharge for the last two months with the help of Enzytreat Plus.

After experiencing this success, furthermore another plant trial was conducted @ 120 KLPD (Daund Sugar) with Enzytreat Plus. Thereafter recycling of condensate in fermentation process was started and achieved excellent results and maintained ZLD (Zero Liquid Discharge).

Note– Control; results obtained without application of Enzytreat Plus

Test; results obtained after application of Enzytreat Plus

Both the factories are achieving zero discharge with 100% usage of condensate in fermentation without any problem by using our product Enzytreat Plus. They have stopped using the CPU completely.

CONCLUSION

This application & technology has several benefits, including major benefits to industries. Such benefits are as follows:

  • Principle benefits-
  • improving ethanol fermentation efficiency
  • increasing wastewater recycling directly without affecting fermentation efficiency
  • decreasing the use of fresh water in the process
  • controlling the formation of the volatile acid within the process
  • improving spent wash quality by volatile acidity & microbial contamination
  • improving other fresh/wastewater streams
  • Environmental & Economical benefits-
  • prevent amount of revenue loses using in treatment of waste water
  • preserve fresh water by recycling such streams directly to fermenter
  • preserve wastage of carbon credits in waste water treatment
  • decrease the toxicity discharge amount to environment
  • eco-friendly and clean product with inexpensive and smooth operation

REFERENCES

  1. Apte S. S., Hivarekar S. B.: Distillery Condensate and Spent Leese Treatment for Complete Reuse – An Approach towards Zero Intake; International Journal of Emerging Technology and Advanced Engineering; Volume 4, Issue 9, September 2014, pp.312-317
  2. S. R.: Treatment and Reuse of Distillery Wastewater; International Journal of Environmental Engineering and Management; ISSN 2231-1319, Volume 4, Number 4 (2013), pp. 339-344
  3. Vandana Patyal: Treatment of Distillery Wastewater by Anaerobic Methods; Int. Journal of Engineering Research and Applications; ISSN: 2248-9622, Vol. 5, Issue 12, (Part – 3) December 2015, pp.151-155