Quick answer: A zero liquid discharge feasibility study is a structured technical and economic assessment that tests whether ZLD is achievable and worthwhile for a specific effluent. It defines objectives, characterises the streams, screens technologies, builds a techno-economic model and delivers a costed recommendation, typically over six to twelve weeks.
Key facts
- A ZLD feasibility study is a decision-support deliverable, not a design package: its job is to confirm whether, how and at what cost ZLD is viable before capital is committed.
- Reliable results depend on good stream characterisation, so representative sampling and a validated water balance are the foundation of the study.
- A typical study runs roughly six to twelve weeks depending on data availability and the number of streams.
- The core output is a techno-economic model comparing viable technology trains on CAPEX, OPEX, cost per m3 and residuals.
- An independent study separates genuine technical fit from vendor sales positioning, protecting a large capital decision.
What is a zero liquid discharge feasibility study?
A zero liquid discharge feasibility study is an advisory assessment that determines whether a plant can eliminate liquid effluent and whether doing so makes technical and economic sense. It answers the question before any equipment is specified or bought.
The study does not design the plant. It de-risks the decision by testing achievability, sizing the likely cost and identifying the constraints that will govern any future design. It is deliberately technology-neutral so that the recommendation follows the data.
Why do industrial sites commission a ZLD feasibility study?
Sites commission a study when discharge is becoming restricted or costly and they need an evidence-based answer before committing capital. The study converts a strategic pressure into a concrete, costed pathway.
Typical drivers include tightening discharge permits, water scarcity and reuse ambitions, corporate sustainability targets, and the need to compare competing vendor proposals on a like-for-like basis. A feasibility study gives management a defensible basis for a go, no-go or staged decision.
What are the objectives and scope of the study?
The objective is to confirm whether ZLD (or a near-ZLD alternative) is achievable for the target streams and to quantify the cost and risk. Scope should be fixed at the outset to keep the study focused.
A clear scope defines which streams are in and out, the recovery target, the boundary conditions and what a “success” answer looks like. It also states explicitly whether minimal liquid discharge (MLD) is an acceptable alternative, because that materially changes the economics.
What data does a ZLD feasibility study need?
The study needs a robust characterisation of every stream: flow, dissolved solids and the specific ions and contaminants present. Weak input data is the most common reason a study gives a weak answer.
The table below lists the core data inputs and why each matters.
| Data input | Why it matters |
|---|---|
| Flow rates (average, peak, seasonal) | Sizes every stage and sets economies of scale |
| TDS and conductivity | Determines membrane recovery limit and thermal duty |
| Major ions (Na, Cl, Ca, Mg, sulphate) | Governs scaling, softening and salt recovery options |
| Silica and hardness | Limits recovery and drives pretreatment design |
| Organics (COD, TOC) | Affects fouling, biological pretreatment and residue quality |
| ZZS / priority substances | Sets discharge limits and residue classification |
| Temperature and pH | Influences equipment selection and materials |
| Existing discharge permit and levies | Anchors the economic baseline |
How is the feasibility study carried out?
The study moves from data gathering through screening to a costed recommendation in a defined sequence. Each step narrows the options using evidence.
- Define objectives, boundary and success criteria with the site team.
- Gather and validate stream data; commission additional sampling where gaps exist.
- Build a water and mass balance for the streams in scope.
- Set the recovery target and test ZLD versus MLD as design cases.
- Screen candidate technologies against the balance and stream chemistry.
- Shortlist one to three viable technology trains.
- Size each train and estimate CAPEX, OPEX and cost per m3.
- Assess residuals: volume, classification and disposal or valorisation routes.
- Review regulatory fit against Water Framework Directive, IED/BAT and Dutch permitting.
- Deliver a ranked recommendation with risks, assumptions and next steps.
How are technologies screened and compared?
Technologies are screened by testing each candidate against the water balance, stream chemistry and recovery target, then comparing survivors on cost and risk. Screening removes options that cannot physically meet the duty before economics are compared.
A typical train is screened in stages: pretreatment, membrane pre-concentration, thermal concentration and crystallisation. The comparison then weighs energy demand, footprint, robustness to fouling, residue quality and total cost per m3, so the recommendation rests on more than headline price.
What are the deliverables of a ZLD feasibility study?
The core deliverable is a written report with a techno-economic model and a clear recommendation. It should give decision-makers everything needed to approve, reject or stage the project.
- A validated water and mass balance for the streams in scope.
- A shortlist of viable technology trains with sizing.
- A techno-economic comparison: CAPEX, OPEX, cost per m3 and sensitivity to energy price.
- A residuals assessment with classification and disposal or valorisation routes.
- A regulatory and permitting review for the Netherlands and EU context.
- A risk register with assumptions and data gaps flagged.
- A ranked recommendation and a proposed next-stage scope (pilot or FEED).
How long does a feasibility study take?
A ZLD feasibility study typically takes six to twelve weeks, driven mostly by how quickly representative stream data can be gathered. Where additional sampling or a pilot is needed, the timeline extends.
Study depth should match the decision. A rapid scoping assessment can screen viability in a few weeks; a full techno-economic study that will underpin a multi-million-euro investment warrants more sampling and modelling.
Netherlands and EU regulatory context
The study must test any ZLD pathway against the regulatory framework that will govern discharge. In the Netherlands and EU this centres on the Water Framework Directive and the Industrial Emissions Directive with its BAT-BREF reference documents.
Discharge permits are issued through the Waterschappen for indirect discharge or Rijkswaterstaat for direct discharge. The ZZS framework for substances of very high concern can tighten limits and shape residue handling. A credible study reads the regulatory trajectory, not just today’s permit, because that trajectory often decides whether ZLD is needed at all.
Common mistakes in ZLD feasibility studies
The most common mistake is basing the study on unrepresentative or incomplete stream data, which undermines every downstream conclusion. A study is only as good as its inputs.
- Relying on a single grab sample instead of representative, time-weighted sampling.
- Fixing on full ZLD without testing MLD as a cheaper alternative.
- Underestimating residuals disposal cost and classification.
- Letting a single vendor’s technology frame the scope.
- Ignoring seasonal and peak flow variation.
- Treating the study as a design package rather than a decision tool.
When to bring in an independent advisor
An independent advisor is the natural choice for a feasibility study because the study’s whole value is an unbiased answer. A study run by an equipment vendor tends to recommend that vendor’s equipment.
Brine Consulting is independent and vendor-neutral. We do not sell equipment, so our screening, modelling and recommendation are built to give you the right answer, not to steer a purchase. That independence is exactly what a feasibility study exists to provide.
Frequently asked questions
What is included in a ZLD feasibility study?
A ZLD feasibility study includes stream characterisation, a water and mass balance, technology screening, a techno-economic comparison of viable trains, a residuals assessment and a regulatory review. It ends with a ranked recommendation, a risk register and a proposed next-stage scope, giving decision-makers a defensible basis to proceed or not.
How much does a ZLD feasibility study cost?
Cost depends on the number of streams, data quality and study depth, so it is quoted per engagement rather than as a fixed figure. A rapid scoping assessment is far cheaper than a full techno-economic study with sampling and modelling. The cost is small relative to the capital decision it de-risks.
How long does a ZLD feasibility study take?
Most studies take six to twelve weeks, driven mainly by how quickly representative stream data can be collected. If additional sampling or a pilot is required, the timeline extends. A rapid viability screen can be completed faster where good data already exists on the effluent streams.
Do I need a pilot before committing to ZLD?
Not always. A feasibility study may conclude that established data and modelling are sufficient, or it may recommend a pilot where stream chemistry is unusual or fouling risk is high. The study is the step that tells you whether a pilot is warranted before capital is committed.
What is the difference between a feasibility study and detailed design?
A feasibility study tests whether ZLD is achievable and worthwhile and produces a costed recommendation. Detailed design comes later and specifies the actual plant for construction. The study de-risks the decision; the design delivers the plant. Commissioning design before feasibility risks building the wrong solution.
Sources and further reading
- European Commission, Water Framework Directive (2000/60/EC)
- European Commission, Industrial Emissions Directive (2010/75/EU) and BAT reference documents (BREF)
- Rijkswaterstaat and Unie van Waterschappen, guidance on industrial discharge permitting (Netherlands)
- Netherlands ZZS (Zeer Zorgwekkende Stoffen) framework, RIVM
- ISO 14046, Water footprint principles and guidelines
- Peer-reviewed literature on ZLD techno-economic assessment (e.g. Desalination, Journal of Cleaner Production)
Talk to Brine Consulting for an independent, vendor-neutral ZLD feasibility study that tests viability and cost before you commit capital.
Written by the Brine Consulting advisory team. The Brine Consulting advisory practice includes Prof. Basel Abusharkh, a specialist in brine valorization, ZLD and high-recovery desalination, and Edwin Muller, a senior industrial water expert with over 25 years across refineries, petrochemicals and power generation. Meet our experts.