Name：Hangzhou Shangtuo Environmental Technology Co.,LTD.
Address: 11# Haishu Road Future Sci-tech City, Hangzhou, Zhejiang, China
There are 7 types of electroplating process wastewater, in which comprehensive wastewater, nickel-containing wastewater and cyanide-containing wastewater can be treated by membrane treatment for water reuse.
There are many sources and the water quality is more complicated, including multi-stage organic acid, alkaline washing wastewater, degreasing wastewater, running dripping wastewater, etc.
Although cyanide is not a type of pollutant, cyanide-containing wastewater contains CN- in wastewater, and it will be reduced to highly toxic cyanide when it encounters acidic substances, which is very harmful to human body and environment.
Electroless Nickel Plating Wastewater:
The composition is more complex and has the following characteristics:
Nickel complexes exist in electroless nickel plating water, and these complexes are all external rail type and have strong complexing properties to nickel;
There are a large amount of hypophosphite and phosphite which have reducing properties in electroless nickel plating water;
There are a large number of pH buffers in electroless nickel plating water, as well as brighteners and stabilizers.
The electroplating wastewater is derived from various baths and water used for pre-plating treatment, plating rinsing, post-treatment, scouring workshop floor, plating tank leakage or improper operation and management, such as drips and leaks. Among them, plating rinsing wastewater is the main source of electroplating wastewater.
The heavy metals contained in the electroplating wastewater are very harmful to the human body. Due to the difficulty in degradation and destruction of heavy metals, if directly discharged into the environment, heavy metals can be enriched in fish and other aquatic organisms as well as in crops. Through the role of drinking water and the food chain, it has a wider and more serious hazard to humans.
Therefore, to treat the toxic material into non-toxic, transfer harmful material into harmless, recycling of precious metals and water recycling is the primary purpose of electroplating wastewater treatment.
Process Flow Diagram (Featured Process)
（1）Comprehensive Wastewater Treatment Process
（2）Membrane Concentrated Water Treatment Process
（3）Cyanide-containing Wastewater Treatment Process
（4）Nickel-containing Wastewater Treatment Process
（1）Comprehensive Wastewater Treatment Process Description
Regulating Tank: Comprehensive wastewater is collected into the regulating tank, the water quality and the amount of water are uniformly distributed under the action of the aeration system, and then the wastewater is lifted to the reaction tank by the lift pump.
Coagulation Tank: The pH is adjusted to be alkaline (pH = 9) in the reaction tank to form a hydroxide precipitate in the metal ions in the wastewater, and a coagulant is added to precipitate the metal hydroxide into a precipitable floc.
Flocculation Tank: Coagulant is added to form large particles, which accelerates the precipitation and prepares for subsequent precipitation treatment.
Sedimentation Tank: Wastewater enter sedimentation tank, effectively separate and remove suspended flocs, can removes most of the metal ions.
Ultrafiltration (UF): Ultrafiltration Membrane can be used to remove the suspended particles, colloids, microorganisms, etc. in water. The micropores on the ultrafiltration membrane are small, it is possible to effectively remove suspended particles, colloids, bacteria, and macromolecular organic substances in various waters. It is widely used as a production equipment for purifying water and a pretreatment device for nanofiltration and reverse osmosis devices because it has the ability of 99% removal of colloids and 100% removal of bacteria and microorganisms in water. The ultrafiltration membrane module used in the ultrafiltration device is produced using domestic leading technology, internal pressure hollow fiber, and the filtration precision can reach 0.02 μm.
Reverse Osmosis (RO) System: Reverse osmosis is a new membrane separation technology developed in the 1980s. RO method has characteristics of high salt removal rate, high water production rate, stable operation, small footprint area and easy operation. RO is the most advanced water treatment technology in the world. Its core component is imported reverse osmosis membrane (RO membrane, space membrane), which can remove more than 99% of particulate matter, organic matter, inorganic salts and bacteria. Microorganisms such as viruses have excellent comprehensive indicators of effluent.
1. The removal rate of Cu2+ can reach above 99%, the concentration is lower than 0.3mg/L.
2. The RO Permeate water can meet the requirement of industrial water. The COD of concentrate water from RO system is less than 350mg/L, but the concentration of Cu2+ is around 1 mg/L, so further treatment is necessary.
（2）Cyanide-containing Wastewater Treatment Process Description
The proposed project uses a common and mature method, the alkali chloride method, which is processed in two steps. In the first step, CN- is oxidized to CNCl by NaClO under alkaline conditions, CNCl is quickly hydrolyzed to slightly toxic CNO-, and the second step is followed by further oxidation of CNO- to N2 and CO2. The removal rate of cyanide is above 99%
The reaction principle is as followed:
First Stage Oxidization: pH = 10 to 11
Second Stage Cyanide Removal: pH = 8 to 8.5
This method is a mature cyanide removal process, cyanide removal needs a proper pH range. The industrial pH meter is used to automatically adjust the alkali dosing rate, and the oxidant is automatically dosed by ORP. After cyanide removal, it is discharged into the integrated wastewater treatment system for subsequent treatment.
（3）Electroless Nickel Plating Wastewater Process Description
Electroless Nickel Plating Wastewater Regulating Tank: The Electroless Nickel Plating Wastewater is collected into the regulating tank, and the water are fully evenly distributed and pumped into the cartridge filter.
Cartridge Filter: It is equipped with 1μg of PP melt-blown filter element, which further prevents particulate impurities from entering the high-pressure pump in the filtered water and damages the RO membrane in the reverse osmosis unit.
Nanofiltration (NF): Nanofiltration is a type of membrane separation technique uses pressure difference as the driving force, intercepting nanoscale particles in the water which is between reverse osmosis and ultrafiltration. Compared with ultrafiltration and reverse osmosis, the removal rate of monovalent ions and organics which the molecular weight is less than 200 is poorer for nanofiltration, but the removal rate of divalent or polyvalent ions and organics which the molecular weight is between 200 to 500 is higher. The system could remove divalent ions and separate salt from raw water, with divalent ions removal rate of more than 95%.
Reverse Osmosis (RO) System: Reverse osmosis, a membrane separation operation that uses pressure difference as driving force to separate a solvent from a solution. Pressure is applied to the liquid on one side of the membrane. When the pressure exceeds its osmotic pressure, the solvent reversely penetrates against the direction of natural permeation. Thus, permeate is obtained on the low-pressure side of the membrane and concentrate is obtained on the high-pressure side. The system could desalinate raw water and reduce the quantity of concentrate, the desalination rate could reach more than 95%.
After the wastewater is treated with the above process, it can meet the requirements of pure water, the conductivity is less than 180μs/cm, and it can be reused for production. The nickel-containing wastewater can achieve zero discharge and create maximum economic value under environmental protection requirements.