Environmental factors that affect microbial growth

(i) the nutrientsmicrobial requirements of microorganisms must include the various raw materials that make up the cells and energy-producing substances, mainly: water, carbon nutrient sydration, nitrogen nutrition source, inorganic salts and growth factorsmolecular formula of the environmental factor cells that affect the growth of microorganisms: C5H7O2N (or C60H87O23N12P)Nutritional needs: aerobic microorganisms: BOD5:N:P: 100:5:1;1, water: components, metabolic processes of the solventAbout 80% of the bacteria are hydrated2, carbon source: carbon content accounts for about 50% of cell dry matter, carbon source mainly constitutes microbial cells containing carbon and supply microbial growth, reproduction and movement of energy, general sewage contains sufficient carbon source3, nitrogen source: the supply of microorganisms to synthesize cell proteins4, inorganic elements: mainly phosphorus, sulfur, potassium, calcium, magnesium and other trace elementsRole: constitutes the cell composition, the composition of the enzyme, maintains the activity of the enzyme, regulates osmotic pressure, provides energy for self-supporting microorganismsphosphorus: nucleic acid, phospholipid, ATP conversionSulfur: Protein component, aerobic sulfur bacterial energyPotassium: Activates enzymesCalcium: Stabilizes cell walls and activates enzymesMagnesium: activated enzymes, chlorophyll an important component 5, growth factors: amino acids, proteins, vitamins and so on(ii) the temperature range ofof various microorganisms varies, about 5 to 80 degrees CThis temperature range can be divided into the lowest growth temperature, the highest growth temperature and the optimum growth temperature (refers to the temperature at which microorganisms grow at the fastest rate)According to the temperature range of microbial adaptation, microorganisms can be divided into medium temperature (20 to 45 degrees C), good heat (high temperature) (45 degrees C or more) and good cold (low temperature) (20 degrees C or less)When the temperature exceeds the maximum growth temperature, it causes the microorganism's protein to rapidly denatureand and the enzyme system to be destroyed and inactivated, and in severe cases can cause the microorganism to dieLow temperature will reduce the metabolic vitality of microorganisms, and then in the state of growth and reproduction stop, but still save its vitality(iii) pHdifferent microorganisms have different pH adaptation rangesThe pH adaptation range for bacteria, linebacteria, algae and protozoa is between 4 and 10Most bacteria are suitable for neutral and partially alkaline (pH-6.5 to 7.5) environmentsThe most suitable pH range should be maintained during the biological treatment of wastewaterWhen the pH of wastewater changes significantly, the adjustment pool should be set up so that the wastewater entering the reactor (e.gaeration pool) is kept in the appropriate pH range(iv) an important factor affecting the effect of biological treatmentdissolved oxygenDissolved oxygen treated by aerobic microorganisms is generally suitable for 2 to 4 mg/L(v) Toxic substancesin industrial wastewater, sometimes with chemicals that inhibit and kill microorganisms, which we call toxic substances Its toxic effect is mainly manifested in the destruction of the normal structure of cells and the deterioration of enzymes in the bacteria, and the loss of activity In wastewater biological treatment, these toxic substances should be strictly controlled, but the permitted range of toxic concentrations, need specific analysis