One of the methods of industrial wastewater treatment is purification with the help of a chemical treatment. In this method of coagulation by adding coagulants chemical and aid, the removal of total solids including suspended solids, colloidal substances and some soluble materials is carried out.
The main application of the sewage treatment package is chemical treatment in the removal of colloidal materials especially from the mineral. A chemical treatment package is used to treat sewage from leather and tannery industries, dyeing and looming, dairies, and detergents and sanitary industries to remove color, suspended solids. TARHOKAR Engineering Company Design chemical treatment coagulation are used for triggering various dimensions such as wastewater treatment, water and wastewater design, manufacture and installation. This package are made up coagulation, flocculation, sedimentation and chemical preparation tanks.
Sewage treatment process colloidal substances in chemical treatment Colloidal substances in wastewater are referred to as materials with a diameter of 0.001 to 1 μm and usually have superficial electrical charge. If these materials are similar in terms of electrical charge, they will repel each other and prevents from clotting in the chemical treatment, and thus the time for these substances to settle will be long and finally the sewage treatment package will occupy a large area. A chemical coagulation package is used for depositing and purifying of these materials in the sewage system.
In the chemical coagulation, initially the PH unit is designed. In this part, considering the acidity or alkalinity of the sewage, it can be converted to neutral or alkaline by injection of commonly used acids or bases in the market.
Industrial sewage by entering a fast coagulation is prepared in chemical coagulation package with mechanical agitators and with the injection of coagulant material such as Alum (depending on the Jar testing as described), The colloidal particles in the waste water are loaded and then in a slow coagulation unit or a chemical coagulation package, the flocculating compounds unburden the colloids and form the coarse particles and finally with regarding to the sedimentation and appropriate time, the fluxes formed in the chemical coagulation package will be separated from the sewage and be purified.
Chemicals treatment of colloidal particles of wastewater As stated, Jar testing is the best instrument to determine the amount of injection and the type of coagulant material in a chemical purification treatment package. In this experiment, a mechanical stirrer (mixer) is used for different periods. The device usually used from 6 beakers, one liter with a specific stirrer and the lighting is made from the bottom and back of the device to see more precisely the test.
Before starting the Jar test, PH measures the total alkalinity, suspended matter in the sewerage or water in order to determine the parameters of the chemical coagulation package. Coagulants in different concentrations are poured into one liter of the sample and exponentially the prepared ingredients are added into beakers, mechanical stirrers start at about one to five minutes with a low circle. The, the mixer are turn out for 15 to 20 minutes to perform the flocculation procedure. During the operation, the formation of flocculates is recorded and after 21 minutes of completion of the test, the settling time of the formed flukes will be recorded. Obviously, in coagulation and flocculation, the amount of coagulant material is always ideal for minimizing the best efficiency for flocculation and certainly the highest amount of coagulant that would definitely produce the best flocculation in a chemical coagulation wastewater treatment package should not be a criterion for determining the amount of Coagulant substance.
After determining the beaker, the results of coagulation and flocculation are accepted, the amount of sludge is measured in a cylindrical or imhoff hopper and in fact, this sludge is the basis for the calculation of the settling pond of the chemical coagulation pack in the treatment of sewage.
Effective factors in the treatment of sewage by chemical treatment In the chemical treatment, factors such as pH, concentration of minerals, organic matter concentration, alkalinity, water temperature, concentration of colorants, concentration of coagulants and aiding, mixing time and intensity are involved in sewage. The following is a brief description of the effectiveness of each these factors in the chemical coagulation and sewage treatment package.
Appropriate PH: Each coagulant will be optimally suited in the range of PH. For example, Aluminum Sulfate or in the commercial term Alum will have the highest solubility in pH between 4 and 7 and the efficiency of the chemical coagulation packet will be optimized for wastewater sewage.
Mineral Concentration (TDS): The higher the concentration of minerals in the sewage, the lower the amount of coagulant is required and the chemical coagulation rate will be higher.
Concentration of organic material: Unlike mineral substances, the higher the concentration of organic matter in the sewage, the more coagulant is needed and the chemical coagulation rate will be lower and the efficiency of the sewage treatment package will be reduced.
Alkalinity: The hydrolysis produces some coagulants such as Alum, H + ion, which reduces pH in sewage. So alkalinity of sewage must be high enough to prevent a decline in optimal PH.
Sewage temperature: Generally, with increasing temperature, the reaction speed increases in the chemical coagulation process.
The concentration of dyes: The presence of colored materials in industrial sewage will reduce the efficiency of the chemical coagulation purification package.
Concentration of coagulant and coagulant aiding: Concentration of coagulant and coagulant aiding in a chemical purification package depends on several factors. Accordingly, the Jar test will determine this concentration under exploitation conditions.
Mixing intensity: If the intensity and duration of mixing exceeds the desired level, the formed flocculates break down and reduce the possibility of coagulation of colloidal particles in the chemical coagulation package.
Methods for rapid mixing in a chemical coagulation sewage treatment Some of the sewage mixing methods used in the purification with the aid of a chemical coagulation package include:
Injection into the venture
Use of baffled pools in a chemical coagulation package
Use of mechanical mixer lavers in the chemical coagulation package
Use of pipe flocculators in a chemical coagulation package
The most common method is to mix the chemical purification and coagulation using mechanical stirrers. It is worth mentioning that pipe flocculators has been considered for lack of power and easy navigation.
Application of Chemical Coagulation Package Chemical coagulation package for heavy metals removal, sewage treatment of carpet cleaning, wastewater recycling, removal of colloid suspended solids in industrial wastewater, removal of color in sewage dyeing factories and application in factories such as starch, dairy and carton buildings are considered as a part of a sewage treatment system or industrial wastewater treatment.
Chemical coagulation leads to relatively high shipping costs due to the use of chemicals. Today, the electric coagulation method is expanding in the treatment of sewage and its cost is much lower.