Zero liquid discharge has moved from a differentiator to an obligation for a growing list of API and intermediate plants. The mistake we see most often is treating ZLD as a single capital purchase — an evaporator bolted onto the end of an existing ETP — rather than as a water balance problem that starts inside the process.
Readiness is a water balance, not an evaporator
Before any MEE or ATFD is sized, the plant needs an honest water and salt balance: every stream, its volume, its TDS, and whether it can be segregated, reused, or recovered upstream of evaporation. Most plants can cut the load they have to evaporate substantially through segregation and reuse — and evaporation is the most expensive water you will ever treat.
Stage the roadmap to the obligation
A ZLD readiness assessment should produce a staged roadmap, not a single price. Segregation and reuse first, RO recovery next, then thermal evaporation sized to the irreducible stream. Each stage has its own capex, opex, and compliance value, and the plant can sequence them against the regulatory deadline and its own cash.
Opex is where ZLD projects fail
A ZLD train that meets the discharge norm but doubles the plant's steam and power bill is a compliance success and a commercial failure. The opex of the recovery train — steam to the MEE, power to the RO, disposal of the recovered salt — belongs in the decision at design stage, alongside the capex. The cheapest litre to treat is the one you never send to the evaporator.
ZLD readiness is a natural Diagnostic Study: a few weeks of stream characterisation and balance work that tells the plant what it actually needs to spend, and when.