From ultra‑tight drift control to running at the ragged edge of scaling, refiners are stacking tactics that cut millions of gallons from cooling tower makeup. Some are even feeding towers treated sewage effluent and recycled blowdown — safely.
Cooling towers are the refinery’s biggest water story. Historical U.S. data shows towers dominate water use — often greater than 90% of a refinery’s demand (pubs.usgs.gov). Evaporative loss typically runs about 1–4 gpm (gallons per minute) per 100 tons of cooling — roughly 0.2% to 1% of flow — while “drift” (entrained droplets carried out with exhaust air) normally runs much smaller at ≥0.001–0.3% of flow (HPAC Engineering) (HPAC Engineering).
Blowdown (bleed‑off) controls total dissolved solids (TDS) to prevent scale and corrosion. Every percent of higher cycles of concentration — the paper defines it as the ratio of boiler feedwater TDS to blowdown TDS — reduces blowdown and makeup volume, dramatically cutting freshwater use. Cooling towers can truly consume 20–50% of a plant’s total water, making optimization essential (Water Technology). The EPA’s WaterSense guide notes that raising cycles from 3 to 6 can cut makeup water by about 20% (nepis.epa.gov).
Refineries have known the leverage for decades. Older U.S. figures show facilities reusing cooling water up to 50×, dropping median water use to ~468 gallons per barrel refined; once‑through systems used ~24× more water for the same duty (pubs.usgs.gov) (pubs.usgs.gov). Indonesian operators are leaning in: Pertamina has publicly tied corporate strategy to reducing water consumption and improving wastewater quality (pertamina.com).
High‑efficiency drift eliminators
Drift eliminators trap and return spray droplets that would otherwise escape with exhaust air. High‑quality cellular designs remove more than 99.9% of drift, cutting losses from roughly 0.1–0.3% of circulation to about 0.001–0.005% (HPAC Engineering).
Southern Nevada Water Authority retrofits reduced drift from ~0.05–0.2% to ~0.001–0.005%, saving ~70,960 gallons per 100 tons of capacity per year (≈2.6×10^5 L/100‑ton‑year) (HPAC Engineering). Scaled to 1,000 tons, that is roughly 700,000 gallons (2.6×10^6 L) saved annually from drift reduction alone. In large repack projects, maintenance often pairs eliminator upgrades with basin and fill hygiene; some operators bring in a cooling tower cleaning service as part of the retrofit plan.
Beyond water conservation, drift control keeps treatments — scale inhibitors, biocides, salts — in the system, reducing environmental discharge, and limits aerosolized pathogens such as Legionella. The UK HSE’s HSG274 Part 1 requires efficient drift eliminators on all fan‑driven towers (HSE via h2ocooling.com). A 10,000‑ton facility (>4 MW) retrofitting high‑efficiency eliminators would conservatively save ~7×10^6 gallons/year (≈26,500 m³/yr) from drift.
Maximizing cycles of concentration (COC)
Each “cycle of concentration” (COC) means the tower’s circulating water is reused that many times before discharge. The paper defines COC as the ratio of boiler feedwater TDS to blowdown TDS. Higher cycles mean less blowdown and makeup. Water savings scale nonlinearly: WaterSense shows COC 2→3 saves ~17%, 2→4 ~25%, 2→6 ~42% (nepis.epa.gov) (nepis.epa.gov). In Southern Nevada’s W.E.T. program, plants averaged CR 2.22→3.45, cutting blowdown about 45% and saving roughly 675,000 gallons/year per 100 tons (≈2.6×10^6 L/100‑ton‑year) (HPAC Engineering).
The limit is scaling. Calcium carbonate, silica, phosphate, and sulfate saturate as water concentrates. Cooling systems typically add acid or phosphate inhibitors to sequester these, but only to a point. To push further, many programs rely on high‑performance scale inhibitors with tight pH control and accurate feed via a dosing pump. Pre‑softening makeup is another lever; a softener or nano‑filtration stage (hardness removal at lower pressure than RO) is often used to enable higher COC.
Tactics extend to controls: tracer‑based controllers and innovative polymers or sensors that “run at the edge of scaling” can automatically trigger blowdown just before precipitation, with Southern Nevada data showing controllers helping lift COC from ~1.85 to ~3.25 (HPAC Engineering) (HPAC Engineering). As a simple anchor, if a 5,000‑ton system runs 8,000 hours/year, baseline water use at 3× COC is about 10 million gallons/year; raising to 6× COC saves ≈2 million gallons/year (~20%). Even going 5×→6× saves about 9% more makeup (nepis.epa.gov). Aggressive concentration greater than ~8–10× in typical systems often triggers rapid fouling unless offset by advanced treatments (acid feed, acoustic cleaning, etc.).
Alternative cooling tower makeup water
Municipal or industrial wastewater is increasingly in play. An eight‑month Saudi Aramco pilot used treated sewage effluent (TSE) with TDS ~1,500 mg/L to replace groundwater. Because the TSE’s Langelier Saturation Index (LSI, an indicator of scaling tendency) was 0–0.5, concentration cycles doubled from ~2 to ~3.5 with no visible scale; blowdown frequency halved and condenser tubes stayed clean (Water Technology). Pathogen monitoring found proper biocides kept Legionella, virus, and coliform counts undetectable in the recirculating loop (Water Technology). The conclusion: “Treated sewage effluent is a viable and sustainable alternative to groundwater as cooling water makeup” (Water Technology).
Blowdown reuse is also rising. A 2024 techno‑economic study found that recycling blowdown delivered higher net water savings (~13%) at lower cost than only increasing cycles via ultra‑purification (Journal of Environmental Management). Pilot trials cleaned blowdown using membrane and activated carbon treatment to about 80 µS/cm conductivity and 60 µg/L TOC, validating reuse (Journal of Environmental Management). In practice, plants deploy membrane systems with activated carbon polishing to meet the target conductivity and organics load.
Within refineries, “stripped sour water” (after H₂S/NH₃ removal) and other process streams are candidates. As an industry overview notes, refineries generate multiple wastewater streams — including sour water and blowdown — that can be recycled in principle (Fluence). Success hinges on contaminant removal (e.g., de‑oiling), corrosion/biofouling control, and regulatory compliance. Typical polishing steps include de‑oiling via oil removal systems and bio‑filtration; some sites choose moving bed bioreactors to manage organics before cooling feed. The Aramco case underscores that strong chlorination can maintain zero‑detect pathogens even with complex makeup (Water Technology). Where stormwater or brackish sources are available, refineries consider desalting using brackish‑water RO, often with ultrafiltration pretreatment to stabilize particulate loads.
The trend is clear: with rising scrutiny on freshwater withdrawals, complexes are piloting high‑reuse towers. A Sinopec site reports more than 60% of cooling makeup from recycled wastewater with more than 99% compliance to targets and fewer exchanger leaks — credited to corrosion/scale inhibitor programs and real‑time monitoring (FM Industry).
Measurement, chemistry, and quantified outcomes
Implementation starts with metering makeup and blowdown TDS to baseline cycles — a step many sites miss but which WaterSense flags as critical (nepis.epa.gov). Chemical programs should be matched to goals: if targeting high COC, many operators upgrade inhibitors and acids, and tune non‑oxidizing/oxidizing corrosion inhibitors and related treatments, with HPAC noting optimized formulations alongside biocides and dispersants (HPAC Engineering). Predictive control using polymer‑tagged sensors has been shown in Southern Nevada to add blowdown reduction while preventing scale (HPAC Engineering).
The savings are tangible. In Nevada’s W.E.T. program, participants averaged about 675,000 gallons saved per 100 tons of cooling per year — about 6.4 million liters (1.7 million gallons) per million‑ton‑hour of cooling — with regional totals over 1 billion gallons saved, mainly via tower improvements (HPAC Engineering). In another context, a Brazilian mall cut potable water use 27% by recycling up to 797 m³/month into cooling towers and toilets (MDPI).
Regulatory momentum matters. Indonesia’s agencies are sharpening focus on reduce‑discharge and efficiency, and Pertamina’s commitments at the World Water Forum align with SDG targets (pertamina.com). Economics support action: avoided freshwater purchases and sewer fees from blowdown cuts often recover capital in a few years, with a 2024 study confirming that improving water quality to raise COC is frequently cost‑effective relative to large water supply costs (Journal of Environmental Management). Indian/OCEAN water prices, or cost of sending blowdown to treatment, further justify these investments.
Combined strategy and operating limits
The biggest wins are stacked. Eliminating drift plus maximizing cycles yields multiplicative savings: drift cuts remove a ~0.2%‑per‑cycle loss pathway, while each extra cycle saves up to 10–20% of blowdown. Achieving CR ~4 instead of 2 (a 40–50% higher cycle rate) and reducing drift from ~0.1% to ~0.005% can halve cooling makeup demand — before considering alternative makeup. Adding recycled process or sewage water — even 30–60% of makeup — can further reduce freshwater needs, as documented by the TSE and Sinopec cases (Water Technology) (FM Industry).
Technically, success depends on quality control when pushing cycles or using alternate feed. That means measuring flows and TDS, and pairing the program with fit‑for‑purpose chemistry and pretreatment — from hardness‑targeted membranes to organics control — so heat exchangers stay clean and efficient. Many refineries standardize around robust pretreatment such as ultrafiltration and selective desalting with brackish-water RO where source water demands it. With water’s rising value and tightening compliance, these strategies deliver measurable savings in both sustainability and operating cost.
