（1).Polishing and polishing wastewater
During the polishing process of parts, the main pollutants in the wastewater are COD.BOD.SS,due
to the presence of abrasives and polishing agents Generally,the following processing procedures can
be referred to for processing:
Wastewater → regulating tank → coagulation reaction tank → sedimentation tank → hydrolysis acidification tank
→ aerobic tank → secondary sedimentation tank → filtration → discharge.
Characteristics and reference processes
of surface treatment wastewater:
（2).Oil and degreasing wastewater
Common degreasing processes include organic solvent degreasing,chemical degreasing,
electrochemical degreasing, and ultrasonic degreasing.
Except for organic solvent degreasing, in other degreasing processes,the main pollutants in wastewater
are pH, SS, COD, petroleum, chromaticity, etc.
due to the presence of alkaline substances, surfactants, corrosion inhibitors,and other degreasing agents.
Generally, the following processing techniques can be referred to for treatment:
Wastewater → oil separation tank → regulating tank → air flotation equipment → anaerobic or hydrolytic acidification
→ aerobic biochemistry → sedimentation → filtration or adsorption → discharge
This type of wastewater generally contains emulsified oil.
Before air flotation, CaCl2 demulsifier should be added to break down the emulsified oil,which is beneficial
for removal by air flotation equipment.
When the COD concentration in the wastewater is high,anaerobic biochemical treatment can be used first.
If it is not high, only aerobic biochemical treatment can be used.
（3).Acid pickling and phosphating wastewater
Acid washing wastewater is mainly generated during the acid washing and rust removal process of steel parts.
The pH of the wastewater is generally 2-3,and there is also a high concentration of Fe2+and SS.
The following processing techniques can be referred to for treatment:
Wastewater → regulating tank → neutralization tank → aeration oxidation tank
→ coagulation reaction tank → sedimentation tank → filtration tank → pH correction tank → discharge
Phosphating wastewater, also known as film wastewater,refers to the chemical treatment
of iron parts in phosphate solutions containing manganese,iron, zinc, etc., resulting in a layer
of insoluble phosphate protective film on the surface,which serves as a spray coating bottom layer
to prevent rusting of iron parts.
The main pollutants in this type of wastewater are pH, SS, PO43-, COD, Zn2+, etc.
（4).Anodizing wastewater of aluminum
The pollutants mainly include pH, COD.PO43-, SS, etc. Therefore,the phosphating wastewater treatment process
can be used to treat the anodic oxidation wastewater.
Harm:
The main toxic and harmful substances contained in wastewater are as follows:
phosphate, emulsified oil, surfactants, and Zn2+.
(5).Handling method:
At present,most surface treatment workshops have achieved varying degrees of water reuse and recycling.
Some factories can achieve 60% water reuse,with a portion of the treated water being discharged into nearby rivers
and another portion being used for fish farming.
After adopting new water treatment technologies,the amount of new water required is greatly reduced.
For example,the surface treatment of a certain factory used to be 1000t/d,but now it is being recycled,
reducing the amount of new water used to 100t/d.
5-1 Neutralization and sedimentation treatment
The wastewater containing alkali, acid, and trace aluminum ions discharged from the washing tank
is first mixed in the workshop and discharged to the neutralization tank of the comprehensive treatment station.
The pH value is first measured.If it meets the requirements,it flows into the multi-stage sedimentation tank.
If it does not meet the requirements,it is adjusted with acid and alkali.
If it is acidic, use sodium hydroxide for neutralization treatment,and aluminum ions will form aluminum hydroxide
precipitate in a pH neutral environment.
After neutralization, the suspended waste liquid is further condensed, settled,and separated using polymer coagulants
(polyaluminum chloride or polyacrylamide).
If the clarified water in the upper part meets environmental discharge requirements,it can be directly discharged or utilized.
The remaining sludge is transported out after dehydration treatment, and the process is as follows:
5-2 Fill the solution completely
① Fill the wastewater storage tank with waste liquid
② Inject the waste liquid into the neutralization tank
③ Inject water into the overflow ports of the flocculation tank,concentrator, and discharge tank.
④ Dissolve the flocculant in water and stir for no more than 5 hours.
⑤ Inject water into half of the neutralization alkali liquid tank,then inject the same amount of 25% alkali solution and stir.
⑥ Inject waste acid solution into the neutralization acid tank.
(6).Neutrality treatment
The waste liquid contains a large amount of sulfuric acid,which needs to be neutralized with NaOH.
The reaction is as follows:
During the neutralization process,the pH value should be controlled within the range of 7 ± 0.5.
6-1 Flocculation sedimentation
Inject the neutralized waste liquid into the coagulation tank and add flocculant while stirring.
The flocculant uses high molecular weight organic compounds,usually polyacrylamide,
with a molecular weight of about 1 million.
The addition of coagulants causes the suspended Al (OH) 4 to form a flocculent state,which is
then injected into the sedimentation tank and stirred while settling,thereby separating the sediment from water.
Clear water overflows from the sedimentation tank into the discharge tank and is then discharged outdoors.
The injection amount of flocculant is calculated according to the following formula:
Q2=0.7Q1T
Q2=0.7Q1T
Q1- flocculant injection rate/L · h-1;
Q2- Mud extraction rate/L · min-1;
T - Agglomeration time/min.
6-2 Separation
The mud in the sedimentation tank is pumped out and sent to a filter press or dewatering machine
for dewatering treatment.
The dehydrated sludge has a moisture content of up to 85% -90%,and its main component is Al (OH) 3 · 18H2O.
6-3 Solution for wastewater reuse in the surface treatment industry
This industry is also a high pollution, high energy consumption,and high water consumption industry,
which brings great difficulties to environmental protection.
The types of wastewater include high organic,high complex, and high heavy metals;we based on the actual situation
of different customers,starts from the perspective of clean production,separates and distributes high-quality water
from the source, and recycles it.
Following the concept of minimizing waste output,we provides customized environmental protection comprehensive
solutions for customers.
6-4 Technical advantages
Flexible combinations and arrangements can be made according to the actual needs of customers,
and the concept of "Industry 4.0" can be applied to electroplating environmental protection.
This not only minimizes the use of chemicals and cleaning water,reduces power consumption,
and achieves resource conservation,but also reduces the emission of high concentration waste liquid,
cleaning wastewater, solid waste, and exhaust gas,achieving micro emissions to zero emissions
and realizing green manufacturing.
Advanced sewage treatment technology.
Due to the separation and concentration of pollutants from sewage by the sewage reuse system,
efficient sewage treatment technology must be used in conjunction with sewage reuseto provide a stable
and compliant treatment solution.
6-5 Supporting wastewater treatment technology
Pure water reuse technology - DYEL-BWRO system;AOP Advanced Oxidation Technology - DYEL-AOP System;
Enhanced Biotechnology - Immersion Aeration Filtration (DYEL-SAF);
Solid liquid separation technology - DYEL-SMF system;Electrochemical Technology - DYEL-EFT System
(7) Applicable industries
Chemical raw material and metal recycling, automotive,building materials, aviation, bathroom, railway, anodizing
and other surface treatment industries.
