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Removal of E. coli from water
  • 2025-07-22

Removal of E. coli from water

Characteristics and risks of Escherichia coli

Toxigenic strains: Shiga toxin-producing strains such as O157:H7

Infection threshold: ≥100 CFU/100mL (GB 5749 mandatory limit)

Transmission route: surface water/shallow groundwater contaminated by feces

Key technical measures

Multi-stage barrier system

Membrane filtration guarantee

Reverse osmosis device (retention rate>99.99%, membrane pore size≤0.0001μm)

Nanofiltration pretreatment (200-500Da molecular weight cutoff)

Ultraviolet disinfection system

Dose control: 40mJ/cm² (inactivation rate 4-log)

Quartz sleeve transmittance>85%

Chemical enhancement scheme

Chlorine contact disinfection (CT value ≥15mg·min/L)

Chlorine dioxide addition (residual amount 0.1-0.8mg/L)

Key points of project implementation

Water source protection:

Groundwater wells are set with a 50m protection radius

10 upstream of the surface water intake 00m no-discharge zone

System redundancy design:

Ultraviolet or chlorine disinfection secondary protection must be configured after the membrane process

Ultraviolet intensity sensor real-time monitoring (alarm threshold 70%)

Treatment efficiency verification

Microbial detection:

Enzyme substrate method (24-hour rapid quantification)

Daily monitoring of total coliform group & heat-resistant coliform group

Membrane integrity detection:

Pressure decay test (△P <10%/min)

Laser particle counter online monitoring

Operation advantage analysis

Ultraviolet system:

No disinfection by-products (avoid chloroform generation)

Operation cost <0.03 yuan/ton (100m³/h scale)

Combined process guarantee:

Maintain biosafety in sudden pollution events

Membrane system and ultraviolet light synergistically achieve 6-log removal rate


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