General Approach

Residential reclaimed water reuse treatment follows a full-process strategy of “Collection & Pretreatment → Biological Treatment → Advanced Treatment → Disinfection & Storage → Segregated Supply by Quality.” Domestic wastewater (gray water) generated from residential communities and office buildings is treated and reused for toilet flushing, landscape irrigation, road sweeping, garage washing, and other miscellaneous purposes, achieving water conservation, emission reduction, and water resource circular utilization. Design follows the Building Reclaimed Water Design Standard (GB 50336) or local reclaimed water design specifications.

Core Technical Routes

① Gray Water Collection + Flow Equalization: Bathing drainage, laundry drainage, and kitchen drainage are collected either separately or combined. Equalization basins balance flow and water quality, controlling influent COD at 200 to 400 mg/L and SS at 100 to 200 mg/L. Applicable to influent collection for residential community and public building reclaimed water stations.

② MBR / AAO Biological Treatment: Membrane bioreactors achieve high sludge concentration and retention, with effluent COD ≤50 mg/L and ammonia nitrogen ≤5 mg/L. AAO processes provide simultaneous nitrogen and phosphorus removal. Applicable as the core treatment stage for reclaimed water systems, achieving stable Class 1A compliance.

③ Sand Filtration + Activated Carbon Advanced Treatment: Quartz sand filters retain suspended solids. Granular activated carbon adsorption removes color, odor, and trace organics, reducing effluent COD and UV₂₅₄. Applicable to scenarios with higher reclaimed water quality requirements such as toilet flushing and landscape irrigation.

④ Disinfection Treatment (Sodium Hypochlorite / UV): Sodium hypochlorite solution dosing maintains residual chlorine at 0.1 to 0.5 mg/L to eliminate pathogenic microorganisms. UV lamps provide supplementary disinfection, suitable for reclaimed water used in spray irrigation systems to prevent Legionella proliferation.

⑤ Reclaimed Water Storage & Distribution: Clear water reservoirs store reclaimed water with volume designed at 25% to 35% of maximum daily water demand. Variable frequency constant pressure pumps provide segregated supply for different reuse purposes. PE or PPR piping materials prevent secondary contamination. Applicable to residential community reclaimed water system design.

Key Considerations

The core principles of residential reclaimed water reuse are “Stability, Reliability, and Convenient Operation.” Reclaimed water quality must comply with GB/T 18920 (Water Quality Standard for Urban Miscellaneous Use). The combined process of “MBR + Activated Carbon + Disinfection” is recommended, providing stable effluent that reliably meets compliance standards.