Pollution of rivers and water bodies by wastewater is a serious problem at present. Wastes from the central sewage system of large cities and other settlements need constant cleaning, so the use of filtering systems and biological cleaning methods is a necessity.
What is activated sludge?
Sludge, which is active against pollutants, is used in domestic septic tanks, industrial enterprises and urban sewer systems. Active sludge, or the biocenosis of zoogenic clusters, is a complex of bacteria and other microorganisms that use human waste for nutrition and reproduction.
Microorganisms and bacteria absorb organic matter from the total mass of effluents and process it into simpler compounds during oxidative reactions. For the productive work of activated sludge it is necessary to create certain conditions: the waste fluid must have a temperature of at least +6 degrees. Wastes should not contain a lot of toxic substances or oil products. Activated sludge is a complex of living organisms that can die during a sharp change in environment. Low temperatures can slow the growth of bacteria, but not kill them.
Sludge concentration
Productive effluent treatment is possible only if a sufficient number of microorganisms affect the contaminated mass. The concentration of biologically active sludge is measured as follows: the amount of dry matter of biomass per unit volume is detected. For 100%, the total mass of all the liquid in the tank is taken. The concentration of activated sludge is measured in percent.
Oxidation processes in sludge of increased concentration will take place much faster, waste recycling will become more productive.
Sludge composition
Active sludge is a mass consisting of flakes 1-3 mm in size. Flakes are formations that consist of bacteria combined with polysaccharides. The composition of activated sludge contains biologically active components, dead microorganisms, suspended particles of inorganic compounds, fiber and other polysaccharides.
Each group of bacteria specializes in the oxidation of certain substances. Filamentous bacteria, nitrifying bacteria and flocculating bacteria oxidize the organic carbohydrate and nitrify the compounds. Bacteria p. Pseudomonas are able to oxidize fatty acids, paraffins, alcohols and hydrocarbons. Oil products, naphthenes, phenols, aldehydes are oxidized by bacteria p. Brevibacterium. Bacteria from p. Bacillus are used to break down aliphatic hydrocarbons. Bacteria p. Cellulomonas oxidize cellulose.
Microorganisms of activated sludge can be fungal in nature. Mold and yeast fungi do a great job in breaking down hard-to-oxidize substances and toxic compounds.
Monitoring the status of activated sludge
The activity of sludge may decrease over time, it all depends on the environment coming in with the sewage. In order for the cleaning process to be productive, it is necessary to monitor the state of the bacterial environment of the sludge.
Bio-indicator control of activated sludge is carried out using microscopic analysis. The features of the structure and composition of the sludge are revealed, and a detailed report and a list of types of bacteria are compiled. The predominance of microorganisms of a certain group indicates a favorable development of the bacterial environment, since bacteria must respond to the incoming stock mass by changing their composition and quantity. For example, when sewage with a high sulfur content is received, thionic bacteria and sulfur bacteria begin to actively develop.
According to the composition of activated sludge, it is possible not only to determine the productivity of processing, but also to make a forecast of the development of the environment, provided that the regime of wastewater intake of the same composition is maintained.
Industrial wastewater treatment
Wastewater, which is a waste of industrial enterprises, contains a large amount of toxins and complex chemical compounds. Once in the environment, effluents cause damage to living organisms and plants, infect groundwater and air. Therefore, each industrial enterprise develops a plan for the disposal of production waste.
Before biological oxidation of effluents, the fluid flow is mechanically cleaned. Filters separate large solid particles of impurities that settle in separate containers. After biological treatment, the liquid is disinfected.
Some enterprises receive useful components from stock waste. The biomass that comes from wastewater treatment can be valuable. The substances used in the production of fertilizers, medicines and other useful substances are released. The possibility of using waste depends on the type of production and the chemical composition of the spent mass. The introduction of activated sludge into the wastewater of industrial enterprises is an inexpensive and productive way to treat waste. Currently, this is the most popular way to dispose of wastewater.
Analysis of changes in the environment of sludge
The study of sludge on the composition is carried out in a special laboratory. For this, a sample is collected in a clean, opaque container. Analysis of activated sludge is carried out 1-2 times a week for 2 months. The effectiveness of sludge is determined by the following indicators:
- dry matter concentration;
- phosphorus content;
- productivity of enzymatic activity;
- respiratory activity;
- condition of cereal silt.
The composition of the sludge is determined using microscopes of different capacities. A reagent of a certain composition is introduced into the mass of activated sludge. For several days, there has been a change in the composition of the sludge and the growth rate of certain types of bacteria. The size of the flakes and the concentration of individual bacteria are evaluated.
Activated sludge treatment steps
The neutralization of complex organic compounds and their oxidation to simple components takes place in several stages:
- Anaerobic oxidation.
- Aerobic oxidation.
- Settling of the mass in the sump.
- Biological treatment with the participation of microorganisms of various nature.
- Separation of liquid from sludge in a sump.
- Dehydration of activated sludge.
- Drying sludge.
Solids, debris and sand are removed before the main cleaning. The size of the suspended particles at the outlet depends on the filter capacity. The collected material from the filters is burned.
During the initial cleaning process, the remaining solid particles are concentrated at the bottom, and light fat-containing substances spread along the surface. The precipitate and the film are removed from the total mass, and the liquid enters the next tank for the next stage of cleaning.
Activated sludge is used for secondary treatment. Water enters the tank with sludge, which is filled with oxygen during the interaction. Such an environment is an ideal condition for the development of bacteria that feed on the organic substances of the liquid, purifying it and releasing carbon dioxide and water. The amount of sludge is constantly growing, as bacteria actively multiply. Excess activated sludge must be periodically removed from the tank.
Anaerobic and aerobic activated sludge bacteria
Nutrition and reproduction of anaerobic bacteria occurs without the active participation of oxygen. More precisely, in the process of oxidative reactions, oxygen is used, which is part of oxygen-containing acids formed from complex organic substances.
Oxidation with anaerobic bacteria is identical to the natural processes of decomposition of organic substances. These processes only proceed much faster due to the high concentration of bacteria in the environment of activated sludge.
As a result of the decay of organics, carbon dioxide and methane are released.
The oxidation processes of aerobic bacteria occur with the active participation of oxygen, which is contained in the liquid. To maintain the amount of oxygen necessary for the life of bacteria, the septic tank should be equipped with a special compressor or aerator. Aerobic activated sludge is a medium that needs a constant and continuous supply of oxygen.
Aerobic-type bacteria break down complex organic substances to simpler ones in a short time compared to anaerobic bacteria. It is less necessary to clean such a septic tank, since the amount of solid waste is much lower. A negative point is the fact that a septic tank that involves aerobic oxidation of effluents is much more expensive than the anaerobic option.
If the drainage fluid ceased to flow into the sewer or septic tank, over time, the bacteria will die from a lack of nutrient medium. The start of the septic tank will be possible only after the introduction of a new active bacterial medium.
Purification and use of spent activated sludge
Activated sludge is a valuable substance. Its content may include elements such as phosphorus, zinc, nitrogen. These trace elements may be useful in agriculture. The use of activated sludge as a fertilizer is possible only if the composition does not contain impurities of heavy metals. Concentrating in plant tissues, metals make vegetables and fruits hazardous to health.
Waste activated sludge is a dehydrated mass. If there are extraneous unnecessary impurities, then the spent dehydrated sludge is treated or disposed of. Purification of biologically active sludge is done only in those cases, if appropriate. Due to chemical reactions, toxic elements are removed from the sludge mass. Heavily contaminated activated sludge, which is of no value to industry, is burned.
Where to buy activated sludge for cleaning
If you are going to put a septic tank on a personal plot yourself, then in the process of arranging a sewer system, the question may arise with the acquisition of activated sludge.
Biological agents for cesspools and septic tanks are sold in the form of liquids or dry substrates. You can buy them in the department of household chemicals for giving. The price depends on the volume of packaging and the composition of the mixture. The packaging describes in detail how to use the product, how much capacity is designed and for how long productive work of the biological composition will be maintained.
When buying a wastewater treatment product, you should carefully familiarize yourself with the composition of the proposed options. It is better to use products with aerobic bacteria. For their active reproduction and nutrition requires an influx of air. Oxidative processes make it possible to get rid of a larger amount of impurities compared to anaerobic bacteria. And the sediment can be used to fertilize the soil.
Optimal conditions for the full functioning of activated sludge
Observance and maintenance of favorable conditions for the development of activated sludge is the key to the successful productive functioning of a treatment plant. The temperature at which there is an active reproduction and nutrition of colonies of bacteria and fungi is + 20-27 degrees Celsius. If the ambient temperature is less than +6 degrees Celsius, the action of microorganisms becomes less productive, and the rate of processing of effluents decreases.
With a change in the composition of the waste, productivity also decreases. Bacteria need a certain amount of time to rebuild. If, for example, oil products were introduced into the bacterial environment, and there are few bacteria responsible for the oxidation of such complex substances, then a certain amount of time must pass for their active reproduction. When a large amount of toxic substances is introduced, the bacterial environment may die.
The composition of the incoming fluid should be a sufficient amount of organic substances: carbohydrate, nitrogen, phosphorus, sulfur, manganese. For the normal functioning of aerobic bacteria, oxygen is needed, so you need to take care of its continuous supply to the liquid.
Finally
Recycling of household waste, based on the processes of decay and oxidation using bacteria, is a natural method of disposal. The safety and productivity of using activated sludge for wastewater treatment makes the process convenient and environmentally friendly, regardless of the scope of this waste treatment method.