Equipment process for acid pickling, degreasing, phosphating wastewater treatment

Equipment process for acid pickling, degreasing, phosphating wastewater treatmentCore processing technology and equipment:

The treatment of phosphorus and fluoride containing wastewater usually adopts "pretreatment+Chemical precipitation (core)+Deep processing (optional)+The process flow of sludge treatment. The following are the key equipment for each stage:

1. Preprocessing unit:

Regulating pool:

Equipment: reinforced concrete tank body or steel tank body, mixer (submersible mixer or side entry mixer), level gaugepHCalculation (optional).

Function: Homogenize water quality and quantity, buffer impact load, and provide stable conditions for subsequent treatment.

grille/Filtering equipment (if required):

Equipment: mechanical grille, basket filter, bag filter, etc.

Function: Remove large suspended particles and impurities, protect subsequent pumps and precision equipment.

pHRegulating pool (initial adjustment):

Equipment: Pool body/Tank body, mixerpHOnline monitoring device, acid-base dosing system (metering pump, storage tank, pipeline mixer).

Function: To remove wastewaterpHAdjust to a range suitable for subsequent chemical precipitation (commonly used for defluorination)pH 6-8Commonly used for phosphorus removalpH 5-6or9-10It needs to be determined based on the specific process.

2. Chemical precipitation unit (core):

Reaction Tank (Series):

Equipment: Multiple pools connected in series/Tank body (usually divided into fast mixing tank and slow flocculation tank), mixer (fast mixing paddle type)/Turbine type high-speed stirring, flocculation frame type/Push type low-speed stirring).

Function: By adding chemical agents, precipitation reactions occur to form calcium fluoride, calcium phosphate (hydroxyapatite), or other metal phosphates/Fluoride precipitation.

Chemical dosing system:

Equipment: Storage tanks (lime milk tank, calcium chloride tankPAC/PFSCanPAMTanks, precision metering pumps (diaphragm pumps, screw pumps), pipeline mixers, flow meters, level gauges, control systems.

Common Medications:

Fluoride removal: generation of calcium salts (lime, calcium chloride)CaF₂ Precipitation (commonly used); Aluminum salt (polyaluminum chloride)PACAluminum sulfate or iron salt (polymeric ferric sulfate)PFSFerric chloride also has a certain fluoride removal effect (generating aluminum fluoride) while removing phosphorus/Iron complex precipitation).

Phosphorus removal: Calcium salts (lime) form hydroxyapatite precipitate; Aluminum salt（PAC）Iron salt（PFS）Generate iron phosphate precipitate.

Flocculant: polyacrylamide（PAMPromote the aggregation of small flocs into large particles of alum flowers, whether anionic or non-ionic.

precipitate/Clarification equipment:

Equipment:

inclined board/Slant tube sedimentation tank: Utilizing the principle of shallow tank to accelerate solid-liquid separation, with a compact structure. A mud scraper is required.

Efficient sedimentation tank (such asDensadeg, ActifloCombined with sludge recirculation, micro sand loading, or high-density sedimentation technology, the efficiency is higher and the footprint is smaller. The core equipment includes mixing zone, flocculation zone, sedimentation separation zone, scraper, sludge circulation pump (and micro sand circulation system).

Clarification tank: such as a mechanical accelerated clarification tank.

Function: Effectively separate the flocs (alum flowers) generated by chemical precipitation reaction from water, and obtain the supernatant (treated water) and bottom sludge

3. Deep processing unit (selected as needed to ensure compliance):

activated alumina/Zeolite adsorption tower (for fluoride):

Equipment: Pressure vessel (adsorption tower), activated alumina/Modified zeolite filter material, water distribution system, backwash system (water pump, storage tank), regeneration system (regeneration liquid storage tank, pump, commonly used)NaOHandH₂SO(₄).

Function: Used when fluoride still exceeds the standard after chemical precipitation. Activated alumina has strong adsorption capacity for fluoride ions and can be regenerated after saturation.

reverse osmosis/Nanofiltration membrane system:

Equipment: security filter, high-pressure pumpRO/NFMembrane components, pressure vessels, cleaning systems（CIP）Control system.

Function: Deeply desalinate and remove residual ions (including fluorine and phosphorus) from chemical precipitation effluent, resulting in good water quality. But the investment and operating costs are high, and the concentrated liquid produced needs further processing.

Ion exchange resin column (rarely used alone for high concentration fluorophosphate, can be used as a deep treatment):

Equipment: ion exchange column, specialized resin (such as defluorination resin), regeneration system.

Function: Remove residual fluoride and phosphate ions.

4. Sludge treatment unit:

sludge thickening tank/Can:

Equipment: Pool body/Tank body, mixer (optional), scraper (gravity concentrator).

Function: Reduce the moisture content of sludge discharged from the sedimentation tank and decrease the volume of subsequent treatment.

Sludge dewatering equipment:

Equipment:

Plate and frame filter press: high dehydration efficiency, low moisture content of mud cake (can reach)60%The following applies to fine sludge (such as chemical sludge) and operates intermittently.

Box filter press: Similar to a plate frame.

Belt filter press: continuous operation, large processing capacity, but relatively high moisture content of mud cake (about)78-85%）.

Centrifugal dewatering machine (horizontal screw centrifuge): continuous operation, high degree of automation, good sealing, but high energy consumption and high requirements for flocculants.

Auxiliary equipment: sludge feed pump, flocculant preparation and dosing system（PAM）Rinse the water pump and air compressor (for pneumatic equipment).

Sludge storage and disposal:

Equipment: sludge silo, transport vehicles.

Function: Store dehydrated sludge and transport it for safe disposal (such as hazardous waste landfill, building materials utilization, etc.). Fluorinated sludge produced by chemical precipitation is usually classified as hazardous waste（HW32?Specific identification is required, and it needs to be managed as hazardous waste.

Equipment process for acid pickling, degreasing, phosphating wastewater treatment