Metal processing cleaning sewage treatment

There is no fixed standard for the influent turbidity of the container flotation machine, which needs to be determined according to the treatment scenario and subsequent process requirements. The conventional range coversdozens to thousands of NTU. The core is to ensure the stable operation of the flotation unit through pretreatment or parameter adjustment.

1. Typical influent turbidity for different application scenarios

The difference in turbidity of influent water is mainly due to the treatment object. The range of common scenarios is as follows:

• Municipal sewage treatment: mainly domestic sewage treatment, influent turbidity is usually100-300 NTU, SS (suspended solids) concentration corresponds to 50-150 mg/L.
• Industrial wastewater treatment:
  • Low turbidity industrial water (such as electronic and food processing wastewater): The turbidity of influent water is about50-200 NTU.
  • High turbidity industrial water (such as papermaking, printing and dyeing, mineral processing wastewater): The turbidity of influent water can be as high as500-5000 NTU, and it is necessary to reduce the load through pretreatment such as grid and grit tank.
• Drinking water pretreatment: treatment of rivers, rivers, lakes and other source water, influent turbidity is greatly affected by the season, rainy season can rise to200-1000 NTU, dry season may be as low as20-50 NTU.

2. Influence of high turbidity of influent water and its countermeasures

If the influent turbidity exceeds the equipment adaptation range, it will directly affect the treatment effect, and targeted treatment is required:

1. Impact:
   • Excessive floc generation leads to thick scum layer in flotation tank, and slag scraping is not timely, which is easy to cause scum backflow and pollute effluent water.
   • Dissolved gas release device is easy to be blocked by fine suspended matter, which reduces the efficiency of dissolved gas and further weakens the solid-liquid separation ability.
2. Response measures:
   • Add pretreatment links, such as adding sedimentation tank and filter tank, to pretreat the turbidity of influent water tobelow 500 NTU.
   • Adjust the flotation process parameters, such as increasing the reflux ratio of dissolved air and water (to 30%-40%), increasing the dosage of flocculant, and enhancing the pollutant capture capacity.

3. Suggestions on the Control of Turbidity of Inflow Water

In order to ensure the stable operation of the air flotation machine, it is necessary to control the turbidity of influent water from the source:

• Install online monitor: real-time monitoring of influent turbidity, when the value exceeds a preset threshold (such as 500 NTU), trigger an alarm and automatically adjust the pretreatment or dosing system.
• Quality separation treatment: separate collection of high turbidity wastewater (such as workshop washing water), pretreatment (such as coagulation precipitation) to reduce turbidity, and then into the main treatment system.
• Regular troubleshooting: check the operation status of front-end pretreatment equipment (such as grid, grit chamber) to avoid suspended solids entering the air flotation unit due to equipment failure.

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Metal processing sewage treatment equipment Air flotation machineequipment commonly used in metal processing sewage treatment, is through the passage of air into the sewage, generating tiny bubbles, so that suspended particles, grease and other impurities attached to the bubbles, with the bubbles rise to the water surface, so as to achieve solid-liquid separation equipment. The following are related introductions:

operating principle

First of all, under certain pressure (0.35-0.45Mpa), a proper amount of air is sucked through a jet device to form a saturated dissolved air carrier with reflux water in a dissolved air tank. The saturated dissolved air carrier is suddenly released by a release device under reduced pressure to generate a large number of fine bubbles with diameters of about 30-50um. These bubbles quickly adhere to particles, emulsified oil, fibers and other impurities in water and flocs formed by coagulation reaction. Since the overall density of flocs attached with bubbles is lower than that of water, will be forced to float rapidly on the water surface to realize solid-liquid separation, scum will be scraped away, and separated water will enter the clean water tank through the perforated pipe at the bottom.

types and characteristics

• Dissolved air flotation machine: using pressurized jet, high dissolved air efficiency (80%-90%), large dissolved air volume, fine particle size of released microbubbles (10- 20m), good scum separation effect, high degree of automation, easy to operate.
   
• Cavitation air flotation machine: no circulating pump, air compressor, pressure vessel, saving operating costs and floor space, simple configuration, high cost performance, especially suitable for oily sewage treatment.
   
• Ultra-efficient shallow flotation machine: using shallow pool theory and zero-speed principle design, set coagulation, flotation, skimming, precipitation, scraping mud in one, hydraulic retention time is short (5-10min), purification capacity is large, surface load is high, suspended matter removal rate can reach 90%-99.5% or more.

range of application

Widely used in metal processing sewage treatment, can effectively remove suspended solids, grease, glue substances and other non-dissolved substances in sewage, oily wastewater, emulsion wastewater and wastewater containing fine suspended particles treatment effect is remarkable.