in the normal operation of sewage treatment, severe sludge swelling will not occur in high temperature summers and cold winters, and often occurs in spring, summer and autumn/winter seasons. that is, the environment where temperature, water temperature, and air pressure alternate.
1, season expansion time
after analyzing the statistical data of a sewage treatment plant, the period of occurrence of the bubble phenomenon is: when the water temperature is higher than the temperature, the water temperature is changed to when the water temperature is lower than the temperature (from late march to mid-april) and the temperature of the water is lower than the temperature. when the water temperature is higher than the temperature (from late october to mid-november).
2. seasonal expansion analysis
as a result of changes in the ecological environment, the growth and composition of microorganisms have changed. from the past operation and operation, it was found that without changing other conditions, the foam phenomenon will gradually disappear after a period of time (10 to 20 days), and the sewage treatment system will be automatically restored.
through microscopic examination, it was found that the foam in the spring-summer alternation was mainly an outbreak of filamentous bacteria, filamentous bacteria grew in a large amount and spread out, and in autumn and winter, the deactivated filamentous bacteria were enwrapped in similarly inactive bacteria. a floating foam is formed in the micelles.
the principle still needs further study. it is generally believed that when the season (temperature, pressure) alternates, microorganisms will be affected, but the adaptability of filamentous bacteria is stronger than that of some flocks, such as the growth temperature of microthrix parvicella 8 ~ 35 °c, and more suitable for growth in low temperature environment.
when the environment is not conducive to the growth of microorganisms, mycelia of filamentous bacteria will expand from the bacterial micelles to increase their surface area for nutrient intake, and their growth rate is higher than other microorganisms.
when the spring and summer change, the activity of the sludge is reduced. there are a large number of synthetic detergents and oils and fats in the domestic sewage that are not degraded. some filamentous fungi are still active. they like to use these substances as food and grow rapidly. this caused the outbreak of filamentous bacteria and the formation of foam.
when the autumn and winter seasons alternate, the main formation is the floating sludge (this is different from the former). it is difficult to find out the filamentous bacteria that are spreading in the floating sludge and foam. the microscopic bubbles can be seen in the floating sludge. it is estimated that this is when the environment alternates, the bacterial micelles become finely dispersed, and the aeration bubbles are combined to reduce the density and float.
3, seasonal expansion control method
after summing up the rules for the formation of bubbles, it is beneficial to take control measures, such as mechanical cleaning and scraping for foams in spring and summer. because there are a lot of filamentous bacteria in these foams, they should not be left in the mixture so as to avoid re-inflation. in addition, adding a fungicide will have a certain control effect, but it should be careful. as for the floating sludge and foam during the alternating autumn and winter season, high-pressure water jets can be used to relieve the water, because most of the floating sludge is still flocculent and can be returned to the mixture after it is broken.
article source: new environmental protection classroom
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