Greywater Recycling Tank For Data Center: Treatment And Reuse Loops
Created on 10.29
Greywater Recycling Tank For Data Center: Treatment And Reuse Loops
A greywater recycling tank for a data center captures low-contamination streams from restrooms and supporting facilities, treats them through membrane bioreactor (MBR) or ultrafiltration (UF) trains, and stores the clarified effluent as a dedicated non-potable reserve for cooling-tower makeup and toilet flushing. The tank is the buffer between an intermittent or variable treatment output and a steady reuse demand; it is never cross-connected to potable supply without backflow-protected break-tank separation. Sizing follows the treated-flow balance and reuse demand, not the chilled-water loop, and the internal finish must resist biological growth because the tank can sit partly full between treatment batches.
Data centers consume water mainly through cooling towers, but the occupied support buildings on a campus — offices, workshops, restrooms — also generate a predictable, low-contamination wastewater stream that is routinely sent to municipal sewer. Treating and reusing that greywater on site closes a loop that would otherwise be pure loss. The mistake operators make is assuming "recycled water" needs drinking-water treatment, or sizing the storage to the cooling load instead of to the treatment and reuse balance. Get those two wrong and the tank is either over-built or biologically fouled within a season.
This guide works the greywater recycling tank for a data center from source separation through treatment to reuse, and sets out the material and sizing choices that keep the reserve clean, separated and genuinely useful.
Source Separation: What Counts As Greywater
Greywater is the non-blackwater fraction of building discharge, and only a defined subset is worth capturing on a data-center campus. Blackwater (toilet and medical waste) is excluded; the captured stream is the relatively clean, low-pathogen discharge that can be treated on site without full sewage-plant infrastructure.
1. Restroom hand-basin and shower water. The primary greywater source on a campus with occupied buildings; relatively low in solids and easy to pretreat.
2. Supporting-facility washdown and janitorial water. Predictable flows from workshops and maintenance areas, screened for detergents and grit.
3. Explicitly excluded blackwater. Toilet discharge and any contaminated process water stay on the sanitary sewer; mixing them reclassifies the stream and forces a far higher treatment grade.
The cleaner the separated source, the smaller and cheaper the downstream treatment train, so the building drainage should be split at the point of generation rather than re-sorted after collection.
Treatment: MBR And UF Trains For Reuse-Grade Water
Treating greywater to reuse grade means removing suspended solids, organics and microorganisms to the level the reuse demands — not to drinking standard. Two membrane routes dominate on-site recycling.
· Membrane bioreactor (MBR). An activated-sludge stage coupled to microfiltration or ultrafiltration membranes; produces a low-turbidity effluent suitable for cooling-tower makeup and toilet flushing, with a compact footprint relative to conventional clarification.
· Ultrafiltration (UF). A physical barrier (typical pore rating around 0.01–0.1 µm) that removes suspended solids, colloids and most bacteria after a pretreatment stage; often paired with downstream disinfection for aerosolising reuses.
· Disinfection where required. UV or controlled chlorination is applied before any reuse that can create aerosols (cooling-tower drift, toilet flushing mist) to limit legionella risk.
The treated effluent is what fills the recycling tank, so the tank volume is sized to the treated-flow balance and the reuse demand — not to the storm or chilled-water systems.
Treatment route | Typical removal | Best reuse fit | Footprint note |
MBR | BOD, TSS, bacteria, some nutrients | Cooling-tower makeup, toilet flushing | Compact, integrated biology + membrane |
UF + pretreatment | Suspended solids, colloids, bacteria | Toilet flushing, irrigation | Needs separate biologic or chemical stage |
UF + UV/disinfection | As above + pathogens | Aerosolising reuse (tower, flushing) | Disinfection skid added |
Reuse Loops: Where The Recycled Water Goes
The recycling tank earns its place only when a defined reuse consumes the treated volume faster than it idles. Two reuses dominate a data-center campus.
· Cooling-tower makeup. The largest steady sink; recycled greywater offsets potable makeup provided scaling, conductivity and biological fouling are controlled at the tower through blowdown and dosing.
· Toilet flushing. Steady, building-associated demand in occupied support buildings that offsets potable use directly and locally.
A site with heavy cooling demand but limited occupied floor area will under-use a greywater tank sized only for flushing; conversely a people-heavy campus with modest cooling load needs a tank that absorbs flush and washdown demand without overflowing during low-treatment periods.
Storage: Material, Finish And Biological Control
A greywater recycling tank holds biologically active water that can sit partly full, so the internal finish must resist filming, odour and microbial growth. Bolted steel with a smooth, inert lining is the natural choice.
· GFS (glass-fused-to-steel). Enamel fired at 820–930 °C gives a non-porous internal skin (Ra < 0.8 µm) that stays clean through idle periods and is easy to inspect — well matched to intermittent recycled storage.
· FBE (fusion-bonded epoxy). A documented lining for sites that require a specified coating standard and a defined pH tolerance.
· Biological controls. Sealed roof, inlet distribution that avoids short-circuiting, and access for periodic cleaning keep the reserve usable; NSF/ANSI 61 and WRAS listings confirm the lining is acceptable for contact with water intended for non-potable reuse.
Sizing is by the treated-flow balance and reuse demand, with the tank acting as the buffer that lets a batch-treatment plant feed a continuous reuse without a storage shortfall.
Material | Internal finish | Biological resistance | Coating documentation |
GFS bolted | Enamel, Ra < 0.8 µm | High (smooth, inert) | ISO 28765, spark test 1,500 V DC |
FBE bolted | Epoxy lining | High | AWWA C550-style lining spec |
Stainless (limited) | Passivated steel | High | Material cert only |
Sizing The Tank To The Treatment And Reuse Balance
The recycling tank is sized from the treated-water supply profile and the reuse draft, with a dead band for treatment downtime. Three numbers set the volume.
4. Average treated yield. The daily volume the MBR or UF train delivers, including its own backwash and downtime allowance.
5. Peak reuse draft. The maximum combined cooling-makeup and flushing demand over the design window, which can exceed average yield during hot, high-load periods.
6. Buffer band. The volume that carries the site through treatment maintenance, storm upset or a reuse spike without dropping below the low-level alarm.
The result is a tank that smooths a variable treatment output into a steady reuse supply, sized in cubic metres against that balance rather than against the cooling or fire systems.
Project Case
A dedicated data-center greywater-recycling reference is not yet part of the delivered portfolio, so this article is written as engineering guidance rather than a project citation. The company's capability to supply large bolted non-potable and process-water reservoirs is demonstrated in adjacent sectors: overseas fire-protection programs have delivered GFS tanks up to 12,261 m³ (India, 3 tanks, 2024-06) and 1,666 m³ (Singapore, 2 tanks, 2026-01), built to the same bolted-tank standards a greywater recycling tank is engineered to. Those references evidence large-volume bolted-tank supply and QA; they are fire-protection projects, not data-center greywater installations, and are cited here only as capability context.
Center Enamel Engineering Capability
Center Enamel (Shijiazhuang Zhengzhong Technology Co., Ltd) has designed and fabricated bolted storage tanks since 2008. As the first glass-fused-to-steel (GFS) tank manufacturer in China, the company holds close to 200 enamel-related patents, produces roughly 300,000 enamel-coated steel plates a year, has completed more than 30,000 installed projects and supplies its tanks to over 100 countries. The new 150,000 m² production base was added to raise output capacity, and single tanks are supplied up to 60,000 m³. Manufacturing runs under ISO 9001 and ISO 45001, with product certification including NSF/ANSI 61, WRAS, FDA, LFGB, CE (EN 1090), ISO 28765, FM, BSCI and EUROCODE, and design referenced to AWWA D103-09, AWWA C550, NSF/ANSI 61 and WRAS where the application requires it.
For greywater and non-potable reuse duty the company supplies GFS and FBE bolted tanks with sealed roofs, inlet distribution and access specified for intermittent, biologically active storage, and provides the coating and spark-test documentation needed for water-contact review.
Frequently Asked Questions
Q1: What counts as greywater in a data-center campus?
A1: The non-blackwater fraction — restroom hand-basin and shower water, plus screened washdown and janitorial water from support buildings. Toilet discharge and contaminated process water are excluded as blackwater.
Q2: Does greywater need drinking-water treatment?
A2: No. It is treated only to the level its reuse demands, typically through MBR or UF plus disinfection, not to potable standard. Over-treating is wasted capital and energy.
Q3: How is the recycling tank sized?
A3: By the treated-water supply profile and the reuse draft (cooling-tower makeup plus toilet flushing), with a buffer band for treatment downtime — not by the chilled-water or fire systems.
Q4: Why choose GFS for recycled storage?
A4: The smooth enamel skin (Ra < 0.8 µm, fired at 820–930 °C) resists filming and microbial growth during long idle periods and is easy to inspect, which suits biologically active water that sits partly full.
Q5: Can the tank connect to potable supply?
A5: Only through a backflow-protected break-tank separation, never by direct cross-connection; the non-potable ring must remain distinct, labelled and signposted.
Q6: Which reuse saves the most water?
A6: Cooling-tower makeup is usually the largest steady sink and the best absorber of recycled volume; toilet flushing offsets potable use in occupied buildings and provides a stable local demand.
Q7: What certification confirms the lining is water-contact safe?
A7: NSF/ANSI 61 and WRAS listings confirm the internal lining is acceptable for contact with water intended for non-potable reuse; the coating and spark-test records are supplied for review.
A greywater recycling tank for a data center turns a predictable building discharge into a measured, separated non-potable reserve — but only when source separation, MBR or UF treatment and a defined reuse are designed together. Separate the greywater at the source, treat it to the reuse grade, keep the distribution labelled and backflow-protected, and size the tank to the treatment-and-reuse balance rather than to the cooling loop. Done that way, the reserve offsets potable demand without ever being mistaken for it.
Talk to an Engineer
For a greywater recycling tank for a data center, send us the greywater sources and their daily volumes, the treatment route you plan (MBR or UF), the reuse demands you want to serve (cooling-tower makeup, toilet flushing), and any potable interface points. We will return a treated-flow and reuse balance with tank size, a recommended GFS or FBE tank specification with sealed roof and access, and a backflow-protected distribution layout with coating and spark-test documentation.
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