Process selection of kitchen waste water treatment
Food waste wastewater is a kind of organic wastewater with high concentration, and its water quality varies greatly with different types, sizes and seasons of waste.
According to the water quality analysis of similar projects, generally, the influent water quality is Bod / COD = 0.3 ~ 0.6, with good biodegradability. Most of COD and SS in the wastewater can be effectively treated by biological treatment process.
According to the characteristics of wastewater containing oil and high concentration of SS, hydrocyclone deoiler and air flotation were used to remove oil and SS in wastewater as pretreatment before biochemical treatment.
Due to the high concentration of COD and ammonia nitrogen in the wastewater, when the biological treatment process is adopted, the COD value of the effluent after pretreatment and biological treatment can generally reach 600 ~ 800 mg / L, which is difficult to reach below 500 mg / L. the characteristics of kitchen waste wastewater are high concentration of pollutants and high content of ammonia nitrogen. The MBR process is adopted, with nitrification, nitrification and ammonia nitrogen Denitrification treatment facilities can effectively remove COD and ammonia nitrogen.
MBR process is used to treat kitchen waste water. Due to its high sludge concentration, the volume of the treatment structure is greatly reduced, the project investment is low, the treatment effect is stable, and the cost performance is high.
Comprehensive regulation tank: after anaerobic fermentation, the wastewater still contains a lot of suspended solids and oil. In order to ensure the normal operation of the subsequent treatment process, the oil and suspended solids in the wastewater must be removed first. Therefore, before the wastewater enters the MBR treatment system, it first enters the cyclone degreaser, and then enters the air flotation tank to remove the oil and large particles in the wastewater.
Air flotation tank: sewage flows into a small filling section equipped with a release device (or gas-liquid mixing pump). The sewage is fully mixed through the micro bubbles generated by the inflation section during the rising process. Due to the imbalance of density between the mixture of gas and water and liquid, a vertical upward buoyancy is generated, which brings Ss to the water surface. During the upfloating process, micro bubbles will be attached to SS, and Ss will be supported and maintained on the water surface by these bubbles when it reaches the water surface. SS floating on the water is intermittently removed by chain scraper.
Biochemical system: the ultrafiltration part of MBR system adopts internal (external) ultrafiltration membrane module and online cleaning system. The pretreated wastewater enters the biochemical tank, that is, the internal (external) MBR biochemical treatment system. MBR biochemical reactor is composed of denitrification tank and nitrification tank, which are two-stage denitrification and nitrification process.
In the nitrification tank, most organic matter is degraded by aerobic microorganism with high activity, and ammonia nitrogen and organic nitrogen are oxidized to nitrate and nitrite, which are returned to the denitrification tank and reduced to nitrogen in the anoxic environment, so as to achieve the purpose of denitrification. In order to improve the utilization rate of oxygen, the high efficiency internal circulation jet aeration system is adopted, and the utilization rate of oxygen can reach 35.
The sludge concentration in the bioreactor can reach 15g / L by sludge reflux, and the microorganisms formed by continuous acclimation can gradually degrade the refractory organic matter in the wastewater. The pre denitrification reactor makes the best use of the carbohydrate in the wastewater. The ammonia nitrogen removal rate of nitrification and denitrification tank can reach more than 90%, the pollutant removal load is high, and the sludge concentration can reach 15g / L.