How to treat wastewater with high turbidity and high salinity economically
Thread Content
This post was last edited by Shi Xiaoqi on 2015-6-30 at 16:07. Our company is engaged in plastic granulation; salt concentration sorting is used for plastic separation. A certain level of salinity must be maintained during cleaning, and potassium carbonate is added from time to time. The COD value is as high as tens of thousands, while the suspended solids level is around 2000–3000 mg/L. After taking samples on-site, polyaluminum chloride and cationic diamide were added; coagulation occurred and a lot of sediment formed, but the color intensity did not decrease. Therefore, a first round of mesh filtration was carried out. Even after adding chemicals again, sediment remained, and the color intensity still hadn’t decreased. The same situation occurred after the second filtration and subsequent addition of chemicals. Don’t use filter paper. Later, filtration through filter paper yielded good results in terms of turbidity and color. Our company currently has structures with 4 tanks, capable of holding 190 cubic meters of water. Originally, it was planned to reuse the wastewater, with the settled sludge being directly pumped into a spiral press for dewatering. I saw in Hang Shijun’s book \"Water Treatment Plants and Equipment\" that wastewater with high turbidity and high salinity needs to be pre-treated first, such as through filtration. I’m wondering how such wastewater can be treated economically without adding more water treatment facilities. Should an activated carbon filter/quartz filter be added? The energy consumption associated with wastewater evaporation, as well as the cost of the equipment, are very high. I would appreciate any suggestions from those with experience in this field
1. An activated carbon filter is not necessary; a sand filter will suffice； 2. The raw water can also be filtered through a filter press before undergoing coagulation and sedimentation ； 3. A decolorizing agent can be added during coagulation and sedimentation.
You can first do a simple test on your own: use a bottle filled with activated carbon and quartz sand for filtering. If filter paper works well for filtration, then can fiber filters be used as well?
I gave it a try last night using powdered activated carbon, and the results were good – no color was detected. However, the cost of this substance is high. After using granular or columnar activated carbon for adsorption, is it possible to remove the adsorbent directly from the water so that the purified water can be reused? Is it still necessary to use an activated carbon filter? Is the activated carbon filter element placed directly in the wastewater, and can it be reused?
It is generally implemented in the form of a filter; after activated carbon is used for adsorption, its cleaning and regeneration efficiency need to be taken into account. Contact a manufacturer to have them help calculate the lifespan of the activated carbon, as its cost is also quite high. Additionally, if a trial run is possible, efforts should be made to reduce the amount of chemicals used as much as possible while maintaining the desired levels of turbidity and color – after all, these chemicals cost money. By filter element, I mean a melt-blown filter element similar to a security filter; could filtering after preliminary precipitation through a chemical addition also achieve the desired effect? It’s best to have the manufacturer (engineering company) give it a try.
OP, I’m not sure how high your wastewater volume is; we have special microorganisms capable of handling water with a salinity level of less than 8%. If biochemical treatment is possible, it is believed that a significant amount of investment can be saved.
I am also considering a quartz sand filter. For the coagulation and sedimentation stage, I plan to use a mixture of polyaluminum chloride and aluminum sulfate, along with cationic diamide. But I’m not familiar with sand filtration and don’t know the specific operating parameters
Our wastewater generation can reach up to 100 cubic meters per day. How do special microorganisms handle this waste, and what are the steps involved in the treatment process?
PAC works well in combination with cationic PAM; it’s possible to conduct dosage experiments in the laboratory to assess its effectiveness. Based on experience, it can ensure effective removal of SS； If chroma removal proves difficult, quaternary ammonium salt decolorizing agents can be added after PAC is introduced, followed by PAM; this should ensure the desired effect ； If sand filtration is to be used, it is more reasonable to apply it after coagulation and sedimentation.
Our company plans to purchase a spiral press-type sludge dewatering machine. If we use a filter press first, should we carry out dewatering first and then proceed with coagulation and sedimentation of the filtrate?