Unity Dye Chem by Arvind Envisol Limited

Unity Dye Chem employs a ZLD system to transform its factory into an environmental-friendly, operationally efficient unit?

About the client

Unity Dye Chem Pvt. Ltd. is the flagship company of Unity Group of Industries and has specialized in manufacturing pigments for more than 37 years. An ISO-9001:2015 company, Unity Dye Chem has strong credentials in the color business and is one of the of the major pigment suppliers for Indian and multinational companies.

The company manufactures specialized pigments for a variety of products such as plastics, rubber, paints, printing inks, cosmetics, pigments dispersions, leather, and more. It uses organic pigment powders of mono azo and dis azo group in yellow, orange and red series. A technology-focused company with high investments in research and development, Unity Dye Chem offers technical service and customized products to clients in USA, Mexico, Australia, Europe, Africa, Asia, and the Middle East.
The company has a manufacturing unit in Khambat taluka, Anand district, Gujarat, India.

Environmental concerns highlighted by the government

In light of the adverse impact of effluents on marine life, the Regional office of the Gujarat PCB at Anand had issued a direction to all industries in the region to establish ZLD facilities instead of draining the effluent in the Bay of Khambat.
This directive was especially applicable to companies who were looking to expand their existing facilities or set up Greenfield ventures.

Unity Dye Chem starts looking for a zero-liquid discharge (ZLD) solution

The washing of the filter press and the chemical preparations during the manufacture of pigments and intermediate dyes at Unity Dye Chem used to generate as much as 100 kiloliters per day (KLD) of effluents, wherein the level of chemical oxygen demand (COD) was as high as 16000-20000 PPM and that of biological oxygen demand (BOD) was more than 4000 ppm.
When rising demand needed Unity Dye Chem to expand their production facilities, the directive by the government galvanized them into looking for a long-term, future-proof solution that would transform their factory into an eco-friendly facility with a much smaller carbon footprint. Moreover, the solution would recycle effluents and use the recycled water, instead of groundwater (having higher TDS), for the factory’s operations.
However, this involved certain challenges.
The effluent type and chemicals in the feed were such that anaerobic treatment would not work properly. Hence there was a need for an out-of-the-box solution.
Unity Dye Chem hence mandated Envisol to find a sustainable ZLD system that would operate perfectly even in these conditions. For almost two years, they evaluated many options for ZLD systems, including ten of Arvind Envisol Limited’s earlier installations.
After a long techno-commercial evaluation, Unity Dye Chem identified Envisol’s Polymeric Film Evaporation Technology (PFET) – which employed a mechanical vapour recompression evaporator (MVRE) – as a sustainable ZLD solution that satisfied all their expectations. The solution would have three elements: 100 KLD pre-treatment section; a 100 KLD MVRE; and a 30 KLD multi effect evaporator (MEE).

Objectives outlined for Envisol

1. Providing the right solution which could work at extremely high COD/BOD levels adhering to the norms set by Gujarat PCB and Unity Dye Chem’s international buyers
2. Recycle 100% water back into the manufacturing process, hence conserve ground water resources and reduce bore-well water usage
3. Affordable solution, since both capex and opex costs of conventional ZLD is prohibitively high.
4. Ease of operation and maintenance, especially considering low availability of skilled manpower
5. Reduce the quantity of sludge, and manage its handling

Envisol’s Solution

Arvind Envisol Limited received the purchase order for the ZLD System in 2017 and successfully commissioned it to the satisfaction of Unity Dye Chem.
The 100 KLD ZLD plant installed at Unit Dye Chem’s factory has three components:
1. Pre-treatment section
2. MVRE section using patented PFET technology (Polymeric Film Evaporation Technology)
3. MEE (Three-stage Multi-Effect Evaporator) section

Pre-treatment section

The effluent first comes to a feed tank of 2*200 cubic meter from the process plant. From the feed tank, effluent is pumped to a dissolved air flotation (DAF) through pipe flocculation, where oil and grease are removed. The DAF outlet goes to a flash mixer for flocculation and to a clarifier, where hardness is removed with dosing chemicals. The clarifier-treated water goes to a PFET feed tank of 150 cubic meter and the clarifier bottom outlet goes to a sludge sump, where sludge is disposed after dewatering by a filter press.

MVRE section using PFET technology

The effluent is pumped from the PFET feed tank to a PFET vessel, where water evaporation is done at a lower temperature under vacuum by passing steam for sensible heating, and vapour is recompressed by means of a centrifugal fan to utilize flash vapour heat. Condensate water (pure water) is collected separately in a 150 cubic meter condensate storage tank, and concentrate is collected in a 150 cubic meter MEE feed tank.
MEE section
Concentrate effluent is fed from the MEE feed tank to the MEE system, where water is boiled under vacuum by passing steam in a three-stage MEE. A thermo vapour recompressor (TVR) is used to enhance the steam economy. After super-saturation stage, salt is precipitated in the flash vessel, which is removed in the basket centrifuge at 15% moisture, and mother liquor is again recirculated in third effect. Condensate water (pure water) is collected in a 150 cubic meter condensate storage tank.


1. The ZLD system recycles 100% of the water consumed, Unity Dye Chem now has a water-friendly, sustainable solution for its growing needs, without having to deplete groundwater resources.
2. Envisol’s ZLD system incurs ~20% less investment and ~25% less opex compared to setting up a conventional ETP-with-RO plant .
3. The design is simple and automated, enabling the entire plant to be handled by 1 single person. In comparison, conventional systems are prone to many variables and hence need skilled manpower to be able to troubleshoot effectively.
4. Quantity of sludge is 1/ 4th of the quantity generated in conventional scheme owing to very little chemical usage

Inlet/Outlet characteristics:

Sr. No Constituent Unit Inlet Outlet
1 pH 7-7.5 7-7.5
2 BOD ppm 3,375 30
3 COD ppm 16,400 150
4 Total suspended solid ppm 202.00 <1
5 Oil and grease ppm 113.2 NIL
6 Total dissolved solids ppm 30,660 300
7 Total Hardness as CaCO3 ppm 2,266 <15

Talking about Envisol’s work with Unity Dye Chem Mr. Jayanti Patel, CEO, Unity Dye Chem said
“Dyeing has always been associated with the lack of water sustainability. However, we at Unity Dye Chem realized the absolute need to become less water-intensive and also more conscious in the way we managed our water, a task easier said than done. Envisol’s processes were a welcome change which allowed us to recycle most of our water at a much more affordable cost than we anticipated. We are now confident that no matter how challenging it may seem; water sustainability is something we are proudly working towards and accomplishing steadily each day. Envisol has been a strong and effective partner in this initiative”

Ashish Kumar, the CEO of Arvind Envisol says
“Unity Dye Chem was a fantastic partner for us, and together we have achieved something deeply fulfilling. The problem statement posed by Unity to us was a big challenge due to the high COD in chemical effluent and I am happy that our design engineers could come up with a custom solution which has worked perfectly for the client.”