Reclaimed Water Design Standards for Irrigation, Industrial, and Cooling Applications

By: Kate Chen
Email: [email protected]
Date: Feb 05th, 2026

Direct Answer:
Design standards for reclaimed water must align with intended use. Irrigation emphasizes safe nutrients and microbes, industrial water focuses on corrosion and scaling, and cooling systems prioritize biofilm prevention, ammonia control, chloride limits, and Legionella management. Correct treatment, monitoring, and disinfection ensure safety, compliance, and operational efficiency.

Note:
This content is written for engineers, consultants, and decision-makers in environmental engineering. Standards cited reflect best practices in industrial and municipal wastewater reuse, aligned with Chinese GB/T 19923-2005, WHO, and US EPA guidelines.

1. Irrigation (Landscape / Agriculture)

Parameter	Unit	Recommended Range	Purpose / Notes
COD	mg/L	≤ 50–100	Limits organic load affecting soil and plant health
BOD5	mg/L	≤ 10–20	Ensures low biological oxygen demand
SS	mg/L	≤ 10–20	Prevents clogging in drip or sprinkler systems
TN	mg/L	≤ 15–30	Avoids nutrient overload
TP	mg/L	≤ 1–2	Prevents phosphorus accumulation
Chloride	mg/L	≤ 250	Prevents leaf burn and soil salinity issues
Fecal Coliform / E. coli	CFU/100mL	≤ 1000	Ensures human and crop safety
pH	–	6.5–8.5	Compatible with most crops
EC	μS/cm	≤ 2000	Controls soil salinity and osmotic stress

Design Notes:

Secondary biological treatment + filtration + UV/chlorine disinfection is standard.
Monitor flow, SS, nutrients, and microbial counts.

2. Industrial Process Water

Parameter	Unit	Recommended Range	Purpose / Notes
COD	mg/L	≤ 50	Prevents interference with chemical processes
BOD5	mg/L	≤ 20	Limits microbial growth
SS	mg/L	≤ 10	Protects pumps, nozzles, and heat exchangers
Total Hardness	mg/L	≤ 200	Reduces scaling in boilers and pipes
Ammonia-Nitrogen (NH3-N)	mg/L	≤ 1–5	Prevents corrosion in copper and brass equipment
Chloride	mg/L	≤ 250	Prevents stress corrosion in stainless steel
DO	mg/L	0.5–2	Minimizes corrosion and biofilm formation
pH	–	6.5–8.5	Compatible with industrial materials
Total Microbial Count	CFU/mL	≤ 100	Reduces biofouling risk

Design Notes:

Combine MBBR/SBR with tertiary filtration and chemical dosing (antiscalants, pH adjustment).
Optimize SRT and HRT to maintain consistent microbial activity.

3. Cooling / HVAC Systems

Parameter	Unit	Recommended Range	Purpose / Notes
SS	mg/L	≤ 5	Prevents sedimentation and blockages
Microbial Total Count	CFU/mL	≤ 500	Controls biofilm growth
Legionella	CFU/mL	Regular testing	Mandatory in many jurisdictions due to aerosolized bacteria risk
Temperature	°C	≤ 35–40	Limits microbial proliferation
pH	–	7–9	Compatible with metal surfaces
Total Hardness	mg/L	≤ 150	Reduces scaling in cooling towers
COD / TOC	mg/L	≤ 10–20	Minimizes organic deposits
Ammonia-Nitrogen (NH3-N)	mg/L	≤ 1–5	Prevents corrosion in copper alloys
Chloride	mg/L	≤ 250	Avoids stress-corrosion cracking

Design Notes:

Recommended treatment: MBBR/activated sludge + filtration (UF/MF) + UV/chlorine disinfection.
Online monitoring: DO, pH, temperature, microbial load.
Apply biocides and automated dosing to reduce biofilm and Legionella risk.

4. Advanced Technical Considerations

Biofilm Carrier Design: PE, PP, or hybrid plastics; optimized for flow, DO transfer, and longevity.
Hydraulic & Process Design: SRT, HRT, and CFD modeling for carrier motion and aeration.
Sludge Management: Control WAS & RAS; consider anaerobic digestion or dewatering for reuse.
Automation & AI: Sensors + SCADA; predictive maintenance for pumps, media, and filtration.
Disinfection Strategies: UV for chemical-free, chlorine/ClO₂ for large-scale, residual control critical.

5. Visual / Digital Presentation Ideas

Flow Diagrams: Wastewater → MBBR/SBR → Filtration → Disinfection → End-use.
Bar/Line Charts: COD, BOD, SS reductions per stage.
Dashboard Mockups: DO, pH, ammonia, chloride, microbial load monitoring.
Interactive Elements: Hover-over explanations of MBBR media, filtration units, and aerators.