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For the municipal wastewatertreatment, cationic polyacrylamide is used to clean water.
Municipalwastewater effluents are the liquid wastes that are discharged to the environment from community’s sewer systems and wastewater treatment plants (WWTPs). These wastes are of two types: sanitary sewage or wastewater, which comes from homes, businesses, institutions, and industries, and storm water, which comes from rain or melting snow that drains off rooftops, lawns, roads, and other urban surfaces. These wastes usually do not include releases from separate storm water sewer systems. The term ‘municipal’ is used in a generic sense and is interchangeable with ‘community’. ‘Municipal’ includes wastewater systems owned by local municipalities, regional municipal governments, provincial and territorial agencies, urban. In addition to effluents, treatment and release of municipal wastewater results in air emissions and solids, including degrit materials, floatables and scum, and bio solids – a product of biological treatment processes.
Several characteristics of sewage:
1 For the sewage quality and treatment technical, domestic sewage has a high mounts of organics, especially the sewage not including toilet sewage.
2 For the sewage quantity, domestic sewage almost has the same amount as rain, which has seasonal and random characteristics, can be used as the city use recycled water.
3 For the construction, the machines which offer the recycled sewage or rain are much smaller than the machines which offer the pure water.
Municipal wastewater has a very huge quantity,with few change. Commonly we can long time use one chemical agent. Municipal wastewater treatment plants use flocculant for cleaning sludge at last, such as Polyacrylamide, which is one kind of high molecular polymer and for industrial wastewater treatment also use Polymerization Ferric Chloride or Polyaluminium Chloride. At first, according to the condition of water, we confirm whether cationic or anionic flocculant should be used. At last, we should use cationic Polyacrylamide to help the sludge get out of water. Cationic Polyacrylamide can be used for domestic sewage, waste water which is included lots of organics. It is mainly used for the flocculation and sediment of suspensions, but has few effect when it is used in acidic solution.
The function of flocculant:
1 In the chemical treatment method, the processing units, which are based on dosing agent to make a chemical reaction, are: coagulation, neutralization, oxidation reduction.
2 For the coagulation process, PAC can be used, so that the large particles in water impurities can be settled down.
3 PAC cannot completely remove and clean the tiny suspended solids in water, so we need to use cationic Polyacrylamide for precipitation
Domestic sewage should be treated with biochemical method. Sludge is the product of domestic sewage treatment, with high content CODs. Sludge dewatering needs cationic flocculants as a dehydrating agent. When the wastewater is being cleaned by chemicals, a large number of soluble contaminants become insoluble solids, which are separated as sludge. So we can say sludge is the concentrated pollutants. Domestic sludge comes from the follows.
1. Sludge comes from the sewage itself, including sediment, solid particles without degradation, etc.
2. Activated sludge from wastewater treatment plant.
Because of the growth of activated sludge must be excluded in order to maintain the activated sludge in a stable concentration. This part of sludge corresponds the pollutant in sewage. After dewatering and compressing, sludge will be sent to other places for making the construction materials, fertilizer, and compost etc. To prevent the recontamination to environment, in process of treatment, toxic and hazardous substances should be removed.
Cationic flocculant can remove the sludge in most of the water. To treat one ton of sewage sludge, the needed amounts of different agents are different, because of different types of sludge, different suppliers of agents, different fields and machines, different flocculating requirements.
Sludge dewatering agent usage:
1 We should be aware of the quality and changes of the sludge to be treated.
2 We should choose dewatering agent which is suit to the characteristics and the type of sludge dewatering machine.
3 We should be aware of the injection point, the reaction conditions and the dosage of dewatering agent.
4 We should be aware of dissolution and storage of the dewatering agent.
Domestic sewage treatment is a relatively simple process, the treated wastewater can be recycled.
CHINAFLOCcationic Polyacrylamide is applied for sludge dewatering machines such as High-speed centrifuges, belt presses, plate and frame filter presses with the following characteristics: high speed flocculation, huge floc, good resistance to compression and shear, easy to collect, easy to separate from filter cloth.