Zero Liquid Discharge for Industries and Model Project by Aquamech

What is Zero Liquid Discharge?

Zero Liquid Discharge (ZLD) is a treatment procedure intended to eliminate all liquid waste from the environment. 

ZLD focuses on economically eliminating wastewater and creating clean water suitable for reuse (e.g. irrigation), thereby saving money and improving the environment.

Public and industrial sectors consume a significant amount of freshwater while generating large quantities of wastewater.

The discharge of wastewater into the aquatic environment causes significant contamination that adversely affects aquatic habitats and public health if treated inadequately.

Wastewater recovery and recycling have become a growing trend in the past decade due to the increasing water demand.

Not only does wastewater reuse reduce the volume and environmental risk of discharged wastewater, but it also relieves the burden from freshwater withdrawal on habitats. 

At the end of your manufacturing phase, a ZLD treatment device uses advanced technical water treatment systems to reduce liquid waste to zero, as the name implies. 

• Handle differences in the contamination and flow of waste
• Enabling changes to the necessary chemical volumes
• Recover roughly 95% of the liquid waste for reuse
• Treat and recover precious by-products from your waste
• For disposal, generate a dry, solid cake

Benefits of Zero Liquid Discharge:

• By reducing waste volumes, the cost associated with waste management is minimized.
• On-site recycling can also result in fewer maintenance needs than treatment that meets strict environmental discharge requirements.
• Reduce off-site wastewater-related trucks and their associated effects on greenhouse gases and the possibility of neighborhood road accidents.
• Improved performance of the environment and the regulatory risk profile for future permits.

Why should Zero Liquid Discharge be mandatory for every Industry?

It’s not like every wastewater manufacturing facility needs zero liquid discharge. However, every industry should consider it for the benefit of the environment.

1. Local discharge regulations might require ZLD:

Residents, particularly farmers, have filed numerous petitions over the years in which the courts have interfered in Tamil Nadu and Rajasthan districts.

The National Green Tribunal (NGT) found the water of the river unfit for irrigation on the basis of an inspection report submitted by the monitoring committee of the tribunal.

Due to this, in spite of having no national policy on the enforcement of the ZLD, the Madras High Court in 2006 and the Rajasthan High Court in 2012 prohibited the discharge of treated or untreated effluents in the Noyyal and Luni rivers.

As a result, the units in the districts of Tiruppur (Tamil Nadu) and Barmer (Rajasthan) were forced to adopt ZLD systems. Read the full report here.

It is necessary to obey the rules and regulations set by the government.

However, as a responsible corporate citizen, in order to prevent environmental contamination, which is likely to remain well ahead of mandatory criteria in line with environmental standards, businesses should adopt ZLD.

2. Is your facility located where there is a challenge of water scarcity:

In an area that has strict limitations on water usage, there is a possibility that regulations are applied to how many pollutants are allowed to be discharged into local waterways. 

Regardless of government regulations, achieving zero liquid discharge shows good economics, corporate responsibility, and stewardship of the environment.

3. High-cost discharge rates might not be feasible:

Fees can be extremely high for industries that generate complex and dangerous wastewater streams and are allowed to discharge their wastewater to local waterways or municipalities. 

Disposal costs can be minimized by running an in-house ZLD facility, more water is reused, and fewer greenhouse gases are created by off-site trucking, which minimizes the effect on local habitats and the environment. In the long run, implementing zero liquid discharge would undoubtedly prove cost-effective. 

4. Avoid Contaminating Groundwater:

A key problem associated with groundwater usage is groundwater depletion, a concept often described as long-term water-level declines caused by continuous groundwater pumping and industry waste getting discharged. 

Twelve years ago, the Coca-Cola factory was forced to shut down. It was accused of having drained the water supply, abused and “wilfully polluted” the groundwater of the Scheduled Tribes group called Eravalas, in Plachimada, Palakkad district, Kerala. Read the full report here.

The portion of the ZLD prevents this wastewater stream from discharging and maximizes the reuse of wastewater to the greatest extent possible, thus reducing the need for additional groundwater removal.

Based on the zone, the West Zone dominated India’s zero-liquid discharge market in 2017.

Model ZLD Treatment System:

The ZLD procedure can usually consist of a three-step process with the following: 

1. Pretreatment and conditioning:

Removes simple things that can be drained or precipitated away from the drainage source, conditioning the water, and decreasing the suspended solids and materials that would either scale or foul during treatment phases.

For this, we can also have a High Rate Solid Contact Clarifier (HRSCC) to remove suspended matter. Dosings are done for precipitation of hardness and silica thus reducing TDS and also lowering the scaling potential of downstream RO plants.

2. Phase-one concentration:

Concentration is achieved with membranes such as reverse osmosis (RO), brine concentrates, or electrodialysis. Such techniques take this stream and concentrate it to a high salinity level and remove up to 60-80% of the water.

There can be the use of single RO or 2 Stage RO or even 3 Stage RO to minimize the quantity of water to be taken to the Evaporator / Crystalliser with a Drier or centrifuge. 

3. Evaporation / crystallization:

The next step is to produce a solid by thermal processes or evaporation, where all the water is evaporated, collected, and reused. The remaining waste then goes from an evaporator to a crystallizer. 

A wastewater treatability study or test should be conducted to know which ZLD treatment is best for your facility.

It simplifies the process and makes some guesswork possible, ensuring that your facility is having the best possible solution for your particular situation.

Keynote of Project Executed:

Aquamech installed a complete Zero Liquid Discharge Plant of 900KLD at IG Petrochem Taloja.

The complete system comprised the following equipment:

• Chemical preparation tanks and dosing pumps for lime, soda ash, dolomite, and polymer. This system was provided for the precipitation of hardness and silica present in water.

• The whole process of precipitation and settling takes place in the High Rate Solid Contact Clarifier (HRSCC). At the bottom of the HRSCC, sludge is collected in the tank and fed to the filter press to form cakes for solid disposal.

• The filtered water from HRSCC is taken to the media filtration vessels, ultrafiltration for removal of suspended matter, color, odor, and colloidal.

• The UF-treated water is passed through two-stage Reverse Osmosis (RO) to concentrate the quantity of water and minimize the final rejection of the second RO.

• The complete plant is operated with a Single MCC cum PLC /HMI-based panel.

• Initially, we commissioned one stream of 550 KLD, ETP treated water, and 2nd phase we would be installing a 350 KLD stream. The final rejects from the second RO for phases 1 and 2 go to a 130 KLD evaporator.