Inside the power industry's quiet water war: why CCGT plants are eyeing zero liquid discharge

A 250 MW power plant in the U.S. West learned the hard way that evaporation ponds can turn into a financial sinkhole. When its groundwater total dissolved solids (TDS, a measure of salts) jumped from 500 to 2,500 mg/L, the site’s three 35‑million‑gallon ponds effectively doubled beyond design. Draining one by truck penciled out at roughly $0.50 per gallon — about $130 per m³ — or $17 million per pond (watertechnologies.com).

Rather than shut down, the operator installed treatment to reclaim the water. Over two years it recovered ~60 million gallons for reuse and “saved over $20 million” in avoided hauling and outage costs (watertechnologies.com).

That case study is a cautionary tale for combined‑cycle gas turbine (CCGT) plants, whose wastewater streams span [cooling‑tower blowdown, boiler blowdown](https://beta.co.id/en/blog/inside-the-quiet-workhorse-of-a-ccgt-how-online-control-and-maintenance-turn-blowdown-into-compliance-heat-and-savings), condensate polishing waste, ion‑exchange regenerants, and chemical cleaning effluents (text-id.123dok.com). On sites that deploy condensate polishing, wastes from a condensate polisher and ion‑exchange resin regenerations are part of the mix.

In water‑stressed regions, even CCGTs equipped with air‑cooled condensers are being pushed toward minimal discharge because freshwater is scarce or costly. Policies are tightening worldwide: new Chinese power plants are required to incorporate zero liquid discharge (ZLD), while in India’s Tamil Nadu ZLD is mandated in industry (powermag.com).

Regional water stress and Indonesian rules

Southeast Asia faces an acute water gap, with a ~40% demand‑supply shortfall projected by 2030; the same source notes investment interest could exceed $27 billion by 2025 (southeastasiainfra.com). Indonesia already suffers water stress in many areas (southeastasiainfra.com), and environmental regulators enforce effluent limits; for example, Ministry Regulation 08/2009 sets discharge standards for cooling and boiler blowdown (text-id.123dok.com).

Critics say standards — particularly for discharges to the sea — remain weak, underscoring regulatory uncertainty (mongabay.co.id). Some provinces may impose stricter limits (text-id.123dok.com). That makes ZLD — which eliminates liquid effluent entirely — a strategic hedge.

ZLD definition and market momentum

Zero liquid discharge (ZLD) means treating wastewater so no liquid effluent leaves the site; all water is recovered or evaporated, with only solid residues remaining. It can dramatically lower freshwater intake by [recycling blowdown — turning wastewater into a resource](https://beta.co.id/en/blog/power-plants-are-turning-cooling-tower-waste-into-a-resource-and-edging-toward-zero-liquid-discharge) (smartwatermagazine.com).

The global ZLD technology market was ≈$1 billion in 2021 and is growing ~12% per year, propelled by scarcity and stricter discharge limits; many industries are moving toward ZLD or near‑ZLD (MLD, minimum‑liquid discharge) solutions (smartwatermagazine.com).

In power, designers are increasingly analyzing MLD options because “removing the last fraction of water… adds much cost and complexity” (power‑eng.com). U.S. studies in the 2000s benchmarked costs for each ZLD stage (pretreatment, brine concentration, crystallization), enabling comparisons with alternatives like deep‑well injection or ponds (powermag.com) (powermag.com).

Evaporation ponds: low energy, high land

Evaporation ponds passively evaporate water in lined basins, leaving brine or a salt crust. They require no external energy and minimal technical complexity, but need large area and favorable climate. In the 250 MW case, hauling a full pond at ~$0.50 per gallon (≈$130/m³) would have cost ~$17 million per pond, making emergency disposal prohibitive (watertechnologies.com).

Ponds risk leakage unless carefully lined, with the potential to contaminate soil or shallow aquifers (power‑eng.com). Biological and fouling issues (algae, bacteria) can degrade water quality (watertechnologies.com). For solids control upstream of ponds or membranes, many plants still rely on a clarifier to remove suspended matter.

Brine concentrators: thermal heavyweights

Brine concentrators actively evaporate water using multi‑effect evaporators (MEE) or mechanical vapor compression (MVC). These units, often installed after membranes, can recover 80–95% of wastewater as condensate (smartwatermagazine.com) (powermag.com). In power projects, streams have been concentrated from ~35,000 mg/L TDS to ~220,000 mg/L (22–25%) with >80% recovery (powermag.com).

Scaling control is critical (common scales include CaSO₄ and CaCO₃). Operators deploy “seeded slurry” MEE designs and membrane trains to smooth operations (powermag.com) (powermag.com). Upstream hardness control can include nano‑filtration or a softener, and antiscalant dosing on RO/NF/UF membrane systems is routine; dosing precision typically relies on a dosing pump and specialized membrane antiscalants.

Capital costs are sizable. One analysis put ZLD (pretreatment + evaporation + crystallization) at about 3× the cost of a simpler train at 200 gpm, although optimized designs (omitting a forced‑circulation crystallizer) could cut the premium to 40–50% (power‑eng.com) (power‑eng.com). Energy is the main driver: pilots report total electrical energy around 10–12 kWh per m³ treated (pmc.ncbi.nlm.nih.gov), which inflates O&M. An Oman study found a levelized cost of ~$7.85/m³ for a conventional evaporator‑crystallizer ZLD system (mdpi.com).

Because concentrators produce high‑quality distillate, most recovered water can be recirculated as boiler feed or cooling makeup — applications where a brackish‑water RO front end often pairs well. The remaining brine (commonly ~30–50 g/L after concentration) is much smaller in volume and can either be disposed or sent to a crystallizer.

Crystallizers: the last mile to solids

Crystallizers drive the final brine to salt precipitation, achieving “true” ZLD (water leaves as solids) at very high cost. At a coal plant (750 MW, 200 gpm flue‑gas desulfurization, FGD, flow), full ZLD generated solids requiring disposal, with operating costs estimated at $32.82 per 1,000 gallons — about $8.7/m³ (power‑eng.com).

By contrast, evaporating only to a thick brine and disposing of it (for example, mixed into fly ash) reduced O&M to $4.37 per 1,000 gallons — roughly $1.2/m³ (power‑eng.com). In effect, forcing crystallization can multiply energy — and cost — by about eight times relative to concentration alone. CAPEX is significant as well: one review found a full evaporator/crystallizer package ~40% more expensive than a simple biological treatment for 200 gpm flow, while an earlier estimate put it at ~3× (power‑eng.com) (power‑eng.com).

There is some byproduct upside: a pilot vacuum crystallizer recovered ~80% pure NaCl at a scrap value of roughly €20 per ton, though mixed salts were not valuable (pmc.ncbi.nlm.nih.gov). Most ZLD projects still focus on water recovery and compliance, with solids co‑disposed under solid‑waste rules.

Comparative performance and trade‑offs

• Land and climate: Ponds demand large areas and dry conditions; otherwise, humidity and rainfall can stall evaporation. They are low‑tech but impractical where space or evaporation are limiting (power‑eng.com). Thermal units have small footprints but high energy needs.
• Water recovery: Thermal/membrane concentrators typically recover ~80–95% of water (smartwatermagazine.com) (powermag.com). Ponds can ultimately reach similar fractions slowly. Crystallizers recover essentially 100% by converting the last liquid to solids.
• Energy use: Ponds use zero external energy. MEE/MVC systems consume on the order of 5–10 kWh/m³ (largely for boiling); one study found the MED+crystallizer step ~86% of total ZLD energy at ≈10 kWh/m³ (pmc.ncbi.nlm.nih.gov).
• Costs: Partial concentrate disposal can be relatively cheap (~$1–2/m³), while full crystallization runs ~$8–9/m³ (power‑eng.com). Emergency hauling can dwarf both: in the pond case, trucking cost about $132/m³ (watertechnologies.com). Pilots in desalination report levelized ZLD water costs of $7–14/m³, compared with municipal supply often under $3/m³ (mdpi.com) (mdpi.com).
• Environmental/risk: Ponds can leak or breach (power‑eng.com). Thermal ZLD eliminates liquid effluent but concentrates contaminants in solids, which must satisfy solid‑waste rules.

Cost–benefit calculus for CCGT

The ZLD business case rests on four pillars: CAPEX for equipment, OPEX (primarily energy and chemicals), savings from water reuse, and avoided disposal or penalties. Upstream of reuse, pretreatment trains often combine ultrafiltration to protect membranes and source conditioning via activated carbon or similar media, especially before membrane systems.

Water value: ZLD returns nearly all water to the plant. In the U.S. pond case, reclaiming ~60 million gallons (~227,000 m³) saved ≈$20 million over two years, implying an effective “value” of about $88 per m³ when avoided pumping and outage costs are considered (watertechnologies.com). Where fresh water is cheap — for instance, municipal water at ~$2.85/m³ in Oman — thermal ZLD at ~$7.85/m³ is harder to justify (mdpi.com) (mdpi.com). In Indonesia, raw water from wells or rivers is often inexpensive or subsidized, which weakens the pure water‑savings argument.

Disposal or penalty avoidance: Where discharges are regulated or hauling is costly, ZLD economics improve quickly. The evaporation‑pond alternative of trucking at ~$132/m³ — with a single pond haul approaching $17 million — underscores the stakes (watertechnologies.com). Avoiding a shutdown (loss of power sales) can intensify savings (watertechnologies.com). In Indonesia, legal uncertainty over sea discharges persists (mongabay.co.id), and any future enforcement shift could add substantial implicit penalties.

Byproducts: Salt recovery brings limited revenue. A pilot reported ~80% pure NaCl at ~€20/ton (pmc.ncbi.nlm.nih.gov).

Capital and payback: ZLD CAPEX has been estimated at ~1.4–3× a simpler system at moderate flows; for high flows (>500–1000 m³/day), absolute costs scale up (power‑eng.com) (power‑eng.com). One analysis put conventional ZLD payback at ~7.7 years under favorable assumptions (mdpi.com). Sensitivity spans grid electricity, chemicals, local water prices, land, and downtime costs. For RO feed preparation, polishing with a carbon filter and upstream softening help control fouling and scale before high‑recovery trains such as brackish RO.

Operations: ZLD adds complexity, from nutrient build‑up to membrane fouling and scale. Hybrid designs — for example, evaporating to a thick brine and then mixing with alkaline ash — can balance practicality. In one design, eliminating forced crystallization cut O&M from ~$8.7/m³ to ~$1.2/m³ (from $32.82 to $4.37 per 1,000 gallons), an 85% cut in steaming needs (power‑eng.com). Where raw water is brackish, a staged train with membranes and thermal concentration can be configured incrementally.

Bottom line for CCGT planners

Thermal/membrane concentrators routinely deliver ~90%+ recovery, effectively decoupling CCGT plants from dwindling freshwater supplies (powermag.com) (smartwatermagazine.com). The penalties are cost and energy: full ZLD with crystallizers typically lands in the several‑dollars‑per‑m³ range (power‑eng.com) (mdpi.com).

Where water must be trucked or discharged at high penalty — or where access threatens generation — ZLD can yield rapid ROI, as in the ~$20 million saved over two years in the U.S. pond case (watertechnologies.com) (watertechnologies.com). Where water is inexpensive and regulations lax, payback is less obvious. Over their lifetimes, ZLD systems have shown payback in under 10 years in many industrial scenarios (mdpi.com), especially when discharge alternatives are constrained.

For Indonesian CCGTs, prudence suggests modeling conventional treatment alongside ZLD, with local water tariffs, waste handling costs, and likely policy shifts in view. With Southeast Asia’s water constraints intensifying and global momentum building for reuse (southeastasiainfra.com) (powermag.com), eliminating liquid effluent can turn a challenging waste stream into a nearly 100% reclaimed resource. On plants with extensive boiler pretreatment, polishing steps such as a demineralizer or mixed‑bed unit help align recovered water quality with turbine and boiler needs.

Sources: industry and academic case studies and reviews (power‑eng.com) (smartwatermagazine.com) (smartwatermagazine.com) (powermag.com) (power‑eng.com) (watertechnologies.com) (watertechnologies.com) (power‑eng.com), Indonesian regulatory documents (text-id.123dok.com) and regional water‑stress reports (southeastasiainfra.com).