Why Daegu Data Centers Face a Different Water Problem
Daegu sits inside the Nakdong River basin, where basin-level management plans and Total Maximum Daily Load-style controls govern BOD, total phosphorus, and total nitrogen discharges. Those basin limits directly determine what cooling-tower blowdown and sanitary effluent can carry before they reach the Geumho or the main Nakdong channel. Korean policy treats water as a strategic resource, and the equipment market reflects that: the South Korean data center water and wastewater treatment equipment market is valued at $79.2M in 2026, growing to $125.8M by 2031 at a 9.7% CAGR, with demand for recycling, RO, and advanced filtration explicitly tied to water-scarcity concerns and stricter discharge and reuse rules (MarketsandMarkets, 2026).
Korea is also a colocation innovator. Tomorrow Water, a BKT subsidiary, has signed MOUs with Samsung, Dohwa Engineering, and BNZ Partners to develop the Co-Flow process, which colocates data centers with sewage works; the Jungnang Water Recycling Center project in Seoul reportedly cut treatment plant footprint by 60% using BKT's Proteus technology, freeing land for data center construction and creating a treated-water source for cooling (Tomorrow Water via The Register, 2022-04). Daegu's hot, humid summers push wet-bulb temperatures high enough to drive more evaporation and drift in cooling towers, so the climate itself forces the site toward higher cycles of concentration and more aggressive blowdown treatment before regulatory pressure even applies.
The Two Wastewater Streams a Daegu Site Must Handle
Cooling-tower blowdown is the dominant stream by volume. It is hot, chemically conditioned, and dominated by dissolved solids reaching up to 2,000 ppm TDS, residual biocides and corrosion inhibitors, and leached copper and zinc, running at 30–40°C (Ecologix, 2025). Sanitary wastewater from offices, cafeterias, and humidification is a comparatively low-flow, biodegradable stream that the Tomorrow Water / Co-Flow model explicitly integrates with data center cooling demand as a reuse source (Tomorrow Water via The Register, 2022-04).
The relationship between blowdown and makeup is fixed by cycles of concentration: per Genesis Water Technologies (2025), blowdown equals 1/(CoC − 1) of makeup. At 4 CoC that is 25% of makeup water leaving as blowdown; at 6 CoC it drops to about 20%. Hyperscale AI facilities consume 1.14–1.70 million L/day of water, so even modest Daegu deployments generate blowdown volumes that exceed what most municipal WWTPs will accept without pretreatment (Ecologix, 2025). Designing one train for both streams guarantees that neither is treated correctly.
Sizing Blowdown for a Daegu Climate
The mass balance is the starting point. Per Ecologix (2025), evaporation rate E = (Heat Load × 860) / (ΔH_vap × η), blowdown B = E / (CoC − 1), and makeup M = E + B + drift losses, with drift typically around 0.02% of circulation. For a 50 MW heat load at η = 0.8, that yields E ≈ 99,537 kg/h; at 5 CoC the resulting blowdown is in the same order of magnitude as evaporation, which sets the lower bound for any treatment train (Ecologix, 2025).
For a 10 MW facility on evaporative cooling at 4 CoC, Genesis Water Technologies (2025) gives a working example of around 15 million gallons of monthly intake, with 25%—about 3.75 million gallons—leaving as recoverable blowdown. Daegu's higher summer wet-bulb temperatures push both numbers upward during peak cooling season. Applying a WUE benchmark of 1.8 L/kWh to a 100 MW IT load at PUE 1.2 gives 83.3 MW of IT load, 2,000 MWh/day, and roughly 3.6 million L/day of total water demand, of which evaporative losses are about 60% and the remainder is blowdown plus drift (Ecologix, 2025).
The 4→6 CoC step that operations teams often propose is only a 5 percentage point reduction in blowdown share (25% to 20%) and roughly a 20% improvement in blowdown volume, not 50%; above 5–6 CoC the biological and scaling risk grows exponentially without advanced treatment, so most sites cap themselves before that point (Genesis Water Technologies, 2025).
| Parameter | Value or Band | Source |
|---|---|---|
| Evaporation formula | E = (Heat Load × 860) / (ΔH_vap × η) | Ecologix, 2025 |
| Example evaporation, 50 MW, η = 0.8 | E ≈ 99,537 kg/h | Ecologix, 2025 |
| Blowdown ratio formula | B = E / (CoC − 1) | Ecologix, 2025 |
| Makeup formula | M = E + B + drift (~0.02% of circulation) | Ecologix, 2025 |
| Blowdown share at 4 CoC | 25% of makeup | Genesis Water Technologies, 2025 |
| Blowdown share at 6 CoC | 20% of makeup | Genesis Water Technologies, 2025 |
| 10 MW facility monthly intake at 4 CoC | ~15 million gallons; ~3.75 million gallons as blowdown | Genesis Water Technologies, 2025 |
| WUE benchmark, efficient facility | 1.8 L/kWh | Ecologix, 2025 |
| 100 MW IT, PUE 1.2, daily demand | ~3.6 million L/day; ~60% evaporative | Ecologix, 2025 |
The Daegu Treatment Train: From Makeup to Reuse or Discharge
Pre-treatment for makeup and RO protection uses 5–10 μm screens, multi-media filtration for RO pre-treatment, softening or ion exchange, and antiscalant/pH dosing with an automatic chemical dosing system for antiscalant and biocide control. The Langelier Saturation Index band sits at −0.5 to 0.5 with the Ryznar Stability Index as a corrosion cross-check (Ecologix, 2025). RO modules reduce TDS at approximately 75% recovery, with osmotic flux governed by J_w = A(ΔP − Δπ) and Δπ ≈ 0.4 MPa for a 500 ppm TDS feed; the industrial RO system for blowdown-to-makeup reuse is the workhorse in this slot (Ecologix, 2025).
Blowdown-side physicochemical treatment pairs coagulation/flocculation with a dissolved air flotation system for cooling blowdown or lamella clarification; per Ecologix (2025), precipitation reactors with lime achieve 90–95% metals removal, and SVI is best held at 80–150 mL/g for downstream biological or membrane steps. Biological or membrane polishing uses MBBR or MBR; an MBR system for data center sanitary and reuse streams reports 95–99% COD/BOD removal, with submerged ultrafiltration delivering sub-micron effluent suitable for reuse loops (Ecologix, 2025).
Reuse and discharge targets: closed-loop recirculation limits makeup to under 5% of circulating volume annually, and RO/MBR polishing of blowdown typically yields 50–70% recovery for non-critical applications such as irrigation, toilet flushing, and outdoor washdown (Ecologix, 2025). A UV sterilizer for reuse-loop disinfection handles the final microbial barrier. Sanitary wastewater from staff areas is best handled as a separate MBR flat sheet membrane module for blowdown polishing train, or as a packaged biological plant; the Tomorrow Water Co-Flow model demonstrates that this stream can also become the source of makeup for cooling when the data center is colocated with a sewage works (Tomorrow Water via The Register, 2022-04).
| Stage | Unit Operation | Target Contaminants | Key Design Parameter |
|---|---|---|---|
| 1. Makeup pre-treatment | 5–10 μm screens, multi-media filter, softener, dosing | Suspended solids, hardness | LSI −0.5 to 0.5; RSI as corrosion check |
| 2. RO | Reverse osmosis modules | Dissolved ions, silica | ~75% recovery; J_w = A(ΔP − Δπ); Δπ ≈ 0.4 MPa at 500 ppm TDS |
| 3. Blowdown physicochemical | Coagulation/flocculation, DAF or lamella, lime precipitation | Cu, Zn, suspended solids, particulates | 90–95% metals removal; SVI 80–150 mL/g |
| 4. Biological or membrane polish | MBBR, MBR with UF | Organics, residual suspended solids | 95–99% COD/BOD removal; MBBR loading 2–5 kg BOD/m³·d |
| 5. Reuse / closed-loop | RO/MBR polish, UV, storage, recirculation | TDS, microbes, residuals | 50–70% blowdown recovery; closed-loop makeup <5% annually |
| 6. Sanitary (separate) | MBR or packaged biological plant; Co-Flow integration | BOD, TSS, pathogens | Reuse as cooling makeup where colocation exists |
Korean-Specific Reuse and Discharge Constraints
South Korean environmental regulations and wastewater discharge standards are a primary market driver for the equipment segment, alongside water stress from industrial demand and climate variability (MarketsandMarkets, 2026). Effluent limits consistent with the technical narrative call for TDS well under the 2,000 ppm seen in blowdown and temperature differentials under 5°C relative to receiving water, so the receiving Nakdong and Geumho tributaries are not pushed into thermal pollution (Ecologix, 2025). The Water Environment Conservation Act and Water Quality Conservation Act, combined with the Nakdong basin management plan, are the rule set a Daegu facility is measured against, with basin-level TMDL-style controls on BOD, total phosphorus, and total nitrogen governing what blowdown can carry.
On-site treatment becomes mandatory CAPEX where discharge exceeds municipal limits, where the site commits to high-recovery recycling (for example 70% reuse) or Zero-Liquid Discharge, or where the receiving municipal WWTP cannot accept 1.14–1.70 million L/day of blowdown (Ecologix, 2025). Reuse incentives for treated domestic wastewater are a stated Korean policy lever, which Tomorrow Water illustrates through the Co-Flow colocation model that turns a sewage plant into a cooling-water source (Tomorrow Water via The Register, 2022-04).
A 2026 Implementation Roadmap for Daegu Operators
Stage 1: install metering on makeup, blowdown, evaporation, and drift; quantify true consumption versus usage, since unmeasured losses often run 15–30% above theoretical blowdown (Genesis Water Technologies, 2025). Stage 2: optimize what is already in place—repair leaks, replace once-through cooling, tune blowdown triggers, and add self-cleaning filtration to lower suspended-solids-driven blowdown (Genesis Water Technologies, 2025). Stage 3: simplify chemistry, since complex phosphonate and biocide programs add to the dissolved-solids load and make downstream treatment harder; non-oxidant microbiological control enables higher effective CoC with cleaner blowdown (Genesis Water Technologies, 2025).
Stage 4: deploy a modular, right-sized blowdown train—physical separation plus targeted polishing—sized to 100–300 GPM for most enterprise and colocation facilities rather than hyperscale RO trains that demand dedicated operators and high CAPEX (Genesis Water Technologies, 2025). Stage 5: at sufficient scale and operator capability, integrate blowdown-to-makeup reuse with RO/MBR, combined with on-site water generation or rainwater capture, to approach closed-loop operation (Genesis Water Technologies, 2025). For colocation with municipal sewage infrastructure, the Tomorrow Water Co-Flow model is a Korean path worth evaluating early, since it converts a regulatory constraint—proximity to a WWTP—into a water and energy asset (Tomorrow Water via The Register, 2022-04).
Frequently Asked Questions
What blowdown volume should a Daegu data center plan for at a 10 MW scale?
Per Genesis Water Technologies (2025), a 10 MW facility on evaporative cooling at 4 CoC can intake around 15 million gallons per month, with 25%—about 3.75 million gallons—leaving as recoverable blowdown. Daegu's higher summer wet-bulb temperatures push both numbers upward in peak season, so the procurement ask should be the design worst-case, not a 12-month average.
What treatment equipment is required for Korean regulatory compliance in the Nakdong basin?
Stringent South Korean environmental regulations and wastewater discharge standards are a primary driver of equipment demand, with strong pull for water recycling systems, advanced filtration, reverse osmosis, and wastewater treatment solutions tailored to high-density operations (MarketsandMarkets, 2026). The buyer should request vendor documentation mapping each unit operation—DAF or lamella, MBR, RO, UV, multi-media filter, and chemical dosing—specifically to the basin-level BOD, total phosphorus, total nitrogen, and thermal limits in the Nakdong River basin management plan.
Is it better to design one combined train or separate trains for blowdown and sanitary wastewater?
Separate trains. Cooling-tower blowdown runs at 30–40°C with up to 2,000 ppm TDS, biocides, corrosion inhibitors, and leached copper and zinc; sanitary wastewater is a comparatively low-flow biodegradable stream that the Tomorrow Water / Co-Flow model explicitly integrates with cooling demand (Tomorrow Water via The Register, 2022-04; Ecologix, 2025). Combining them forces a compromise that under-treats blowdown and over-treats sanitary flow.
What is the right supplier-selection check before buying a Daegu blowdown treatment system?
Per Genesis Water Technologies (2025), right-sizing to facility scale is essential: a 100–300 GPM modular system typically fits enterprise and colocation sites, while hyperscale RO trains demand dedicated operators and high CAPEX that do not translate at smaller scale. The buyer should ask the supplier for a reference list of Korean or comparable-climate installations, evidence of compliance with the Water Environment Conservation Act and Nakdong basin requirements, and a quoted commissioning duration for water and wastewater treatment systems in weeks, not a generic range.
