Calculator
Editable inputs
Is the feed / design basis sufficiently characterized?
Is routine liquid discharge or disposal legally available?
Is that liquid route reliable and capacity-sufficient?
Is recovered water valuable or required internally?
Is current liquid disposal cost or logistics materially burdensome?
Does a credible solids / sludge disposal route exist?
Can the site support the energy, operations and uptime burden of advanced or thermal treatment?
Is there a qualified internal user or buyer for a recovered material?
Are non-routine / off-spec storage and fallback routes defined?
Have source reduction, segregation and direct reuse been reviewed first?
Screening result
Save this scenario
The share link stores every input in the URL so you can reopen or send this exact scenario.
Need a project-specific review?
Contact Brine Consulting for an independent review of your data, balances and endpoint options.
About this tool
ZLD is sometimes essential and often oversold. Answer ten questions with Yes, No or Unknown to see whether MLD, ZLD or a managed liquid residual warrants evaluation, and which evidence is still missing.
The logic checks data and upstream options first, then the liquid route and whether solids and off-spec residuals can actually be handled.
Method and equations
Feed basis not characterized → Characterize firstSource reduction, segregation, reuse not reviewed → Review those firstNo liquid route AND credible solids route AND site can support thermal → ZLD warrants evaluationLiquid route available AND (water valuable OR disposal burdensome) → MLD / reuse warrants evaluationLiquid route available AND reliable → Controlled residual / targeted treatment may be sufficientEndpoint unresolvedAssumptions
- Rules are applied in order and the first matching rule sets the direction. There is no weighted score.
- Unknown is treated as "not yet evidenced", never as Yes.
- Valorization is screened as a separate overlay, so product revenue never drives the endpoint.
- Missing fallback storage and missing solids routes are always flagged, whatever the direction.
Limitations
- The output is a direction that warrants evaluation, not a recommendation, requirement or design.
- The screener never states that ZLD is required. That conclusion needs regulatory, technical and economic work on the specific site.
- A numeric readiness score is deliberately avoided because it can hide a fatal evidence gap.
Worked example
A chemical site has characterized its brine (Q1 Yes) and already reviewed source reduction and segregation (Q10 Yes). Its discharge permit is being withdrawn (Q2 No), a licensed landfill will accept mixed salts (Q6 Yes) and the site has steam and operators for thermal plant (Q7 Yes).
- Result: ZLD warrants evaluation.
- If fallback storage for off-spec batches is still Unknown (Q9), the screener adds a critical warning to define upset storage and fallback.
- If no buyer for recovered salt is confirmed (Q8), it reminds you not to bank merchant-product revenue yet.
Change Q2 to Yes and Q5 (disposal cost burdensome) to Yes, and the direction becomes MLD / reuse warrants evaluation, which is usually the lower-risk place to start.
The calculator above opens with these default values. Use Reset to defaults to return to them.
Frequently asked questions
What is the difference between MLD and ZLD?
MLD recovers most of the water and leaves a small, manageable liquid residual. ZLD removes all liquid discharge and ends in solids, which usually requires thermal evaporation and crystallisation, a solids outlet and much more energy.
Why is there no ZLD score?
A weighted score can look acceptable while one fatal gap, such as no outlet for the solids, makes ZLD unworkable. Ordered rules keep those gaps visible.
Why does Unknown block the result?
Unknown means the evidence is not there yet. The screener points you to the missing evidence instead of guessing.
Does "ZLD warrants evaluation" mean I need ZLD?
No. It means ZLD is worth a proper feasibility study for your site. Regulatory, technical and economic work decides whether it is the right endpoint.
Related ZLD guide chapters
More water tools
Brine Consulting screening tool. Results are not a design guarantee, vendor guarantee, regulatory determination or detailed process design, and do not replace project-specific modelling, pilot testing or professional engineering review.