Climate Innovation Compass

Water

Problem Overview: Economical Challenges in ZLD

Industries use ~10-20% of global water demands, but are often responsible for a larger share of pollutants discharged. With increasing regulation and water stewardship, this has changed in the last few years. In India, most regions have now enforced regulations for Zero Liquid Discharge (ZLD) on key industries, whereby the production unit has to reuse all the wastewater produced in their operations. Some of these regulations are considered one of the strictest in the world. ZLD is highly effective in reducing water pollution, but consumes high amounts of energy, driving up costs and carbon footprint. Lack of effective ZLD technologies makes many industrial processes uneconomical.

Core Bottlenecks: Energy Consumption & Sludge Handling

ZLD solutions have been adopted by industries like textiles, pharmaceuticals, tanneries in India, but ZLD has been considered as techno-economically infeasible by most, with challenges due to:

1. Energy Consumption

Traditional thermal processes use high amounts of energy. Advanced systems with RO can recover up to 80% of its liquid waste streams & use less energy but have a limit on salinity. To capture the last 20% of water, adding evaporator and crystallising steps are necessary, which lead to high energy cost ^[1]

2. High Capex

Advanced technologies with low energy have high capex. The systems need to handle high concentration of salt and chemicals, which further increases the cost.

3. Sludge Handling & Disposal

After the final step, current ZLD method leaves a solid waste by-product in the form of dry sludge, often referred to as mixed waste salts that contains high levels of hazardous chemicals and heavy metals.

Existing Approaches and Technology Readiness

Thermal / RO+Crystallization

TRL 9+

Commercial, but high energy penalty and high capex

Electrodialysis

TRL 9+

Issues with energy usage, membrane fouling, limited pollutants

Membrane Distillation / BPMED

TRL 6-7

Low energy, high salinity limits but not commercial yet

Where is the white-space for innovation?

Various approaches have been evaluated by the industry including emerging novel membranes (Forward Osmosis, Membrane Distillation), electrochemical technologies (capacitive deionization), reducing water usage (waterless dyes), but adoption is still a challenge because of the trade-off between energy demands, salinity limits and issues with membrane fouling. Customers need a solution that can convert ZLD from a cost-sink to a profitable value proposition. Most growing startups and incumbents have been working on engineering solutions and already have a head start. The innovation needed for this problem statement will need to be a Science Breakthroughs, that can fundamentally change processes. Some of the pathways include: