Experts in water and bacteria can help answer the questions

First of all, it is not that "once the lack of oxygen becomes stagnant water, bacteria will grow violently", but that the large number of bacteria breeds and consumes a lot of oxygen, and it is difficult for other organisms to survive, resulting in the water becoming "stagnant water", at this time, aerobic bacteria will also die in large numbers, and facultative anaerobic bacteria and anaerobic bacteria can continue to multiply (the smell and blackening of the water body is mainly caused by anaerobic bacteria), until the available organic matter is consumed, and then facultative anaerobic bacteria and anaerobic bacteria will also die in large numbers.

Dissolved oxygen actually refers to the molecular oxygen dissolved in water, which is usually denoted as do, expressed in milligrams of oxygen per liter of water. The amount of dissolved oxygen in water is an indicator of the degree of pollution in the water. Dissolved oxygen is consumed when microorganisms multiply, i.e. the higher the pollution, the lower the dissolved oxygen content.

What does it mean that there is no oxygen, it's naïve. Do you put water in an airtight container with no air? Substances are interpenetrating, and oxygen is dissolved when there is air on the surface of the water.

In addition, green plants in the water, including tiny green algae, are still producing oxygen. Microorganisms are not us, the consumption of oxygen is not so great, a fish can breathe a day with a small bottle of water, think about how long the next bacterium (not as good as a cell of a fish) will breathe? There is a lack of oxygen in the water Many aerobic microorganisms will die, and their corpses will be decomposed and provided to other microorganisms that can adapt to the anoxic environment as food, in fact, there are many impurities in the water, and some algae plants.

It's not just H2O. If you have done microbial experiments, you can know that the S growth curve is closely related to this. If the conditions are met, algae, water, and microorganisms can form a small primitive biosphere that can coexist for a period of time.

The more oxygen there is, the more it grows, which only means that the water is indeed very impure. Find a bottle of pure water, and he will first grow and then decrease, and then stabilize, showing S growth. Oxygen dissolved in water is called dissolved oxygen (DO), and dissolved oxygen exists in water in a molecular state.

If you don't understand anything, please say.

The bacteria that are usually present in water can be broadly divided into three categories:

1) Bacteria present in natural water. The common ones are Pseudomonas fluorescens and Pseudomonas aeruginosa, which are generally considered to be non-pathogenic to healthy humans.

2) Soil bacteria. When there is more surface water during flood times or after heavy rains. They do not survive long in water and are easily removed during water treatment. Iron and sulfur bacteria that corrode water pipes also fall into this category.

3) Gut bacteria. They live in the intestines of warm-blooded animals, so they are abundant in feces. If such bacteria are found in water bodies, they can be considered to have been contaminated with faeces.

Pathogenic intestinal bacteria include Salmonella (typhoid and paratyphoid), Shigella (dysentery) and Vibrio cholerae.

When studying the influence of one condition on the subject of the study, the experiment in which the conditions are the same except for these conditions is called a controlled experiment, and the title is "the effect of water on the life of molds", and bacteria and fungi are collected in various environments as required. The control and experimental groups were cultured in an incubator or in a warm place in the room and it was concluded that bacteria and fungi were widely present.

Certain conditions are required for bacteria and fungi to survive.

In the "Effect of Temperature on Mold Life" experiment, one group of experimental devices can be placed at low or high temperature, and the other group can be placed at room temperature, if it is changed to **"Effect of humidity on mold life", then we should put a group of experimental devices in dry.

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Analysis and discussion of experimental data on bacteriological detection of water quality, 1Errors in sample collection and handling: Sample collection and handling are important when performing bacteriological testing experiments on water quality, as any improper handling can lead to errors in results.

For example, if the sample is not collected rigorously and handled incorrectly, the accuracy of the experimental results will be affected. <>

Bacteriological testing experiments <> water quality raise two questions.

Bacteriological detection, experimental data analysis and discussion of water quality.

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Analysis and discussion of experimental data on bacteriological detection of water quality, 1Errors in sample collection and handling: Sample collection and handling are important when performing bacteriological experiments on water quality, as any improper handling can lead to errors in the results.

For example, if the sample is not collected rigorously and handled incorrectly, the accuracy of the experimental results will be affected. <>

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Analysis and discussion of experimental data on bacteriological detection of water quality, 1In terms of data analysis, it is first necessary to obtain statistical information on the total number of bacteria, including the mean, standard deviation, maximum and minimum values. You can plot the data as a histogram boxplot to understand the distribution.

At the same time, it is necessary to compare the different samples, and the analysis of variance t-test can be used to determine whether there is a significant difference in the side-band. Secondly, the analysis of different bacterial species is required. The proportion of different bacterial species in the total bacterial count can be known by calculating the relative percentages, and further analysis can be carried out based on the ecological characteristics of different bacterial species.

<> pro-family, it is necessary to analyze the experimental results through the discussion and conclusion section of the data, and make suggestions and improvement suggestions based on the conclusions. For example, if the results of the experiment show that the water body is polluted by Heng Xiao, it can be recommended to take effective measures to reduce the source of pollution and continuously monitor the water quality to ensure that the water quality meets the safety standards. <>

Because the surface water is often polluted by soil, industrial sewage, wastewater, domestic sewage and various impurities, it promotes the breeding of bacteria, sometimes the number of bacteria per milliliter of water can reach tens of thousands or even hundreds of thousands, and in some waters, E. coli even reaches tens of thousands. In the process of water treatment, most of the bacteria, coliform bacteria, protobacteria and other microorganisms adhered to the suspended solids are also removed after the purification process of coagulation, sedimentation (or clarification), filtration, etc. However, it is not complete, and there are still a certain amount of microorganisms that are harmful to the human body.

In order to protect people's health and prevent the spread of diseases, water must also be disinfected to kill viruses in the water. China's "Sanitary Standards for Drinking Water" stipulates that the total number of bacteria in water samples cultured for 24 hours after 37 years should not exceed 100 ml, and the number of coliform bacteria in each liter of water should not exceed 3. For this purpose, disinfection is also carried out after coagulation, clarification and filtration.

In industrial cooling water treatment, in order to prevent the circulating water from producing biological slime, the number of heterotrophic bacteria in the circulating water should be controlled not to exceed 500,000 ml, so the filtered water used as supplementary water for the circulating water system also needs to be disinfected and sterilized. In the desalination water treatment system, the raw water of the ion exchange resin also needs to be disinfected and sterilized in order to prevent contamination by bacteria. In addition, disinfection removes the color of the water.

Water disinfection methods can be divided into two types: chemical and physical. Physical disinfection methods include heating method, ultraviolet method, ultrasonic method and other methods. Chemical methods include chlorination, ozone, heavy metal ion and other oxidant methods.

Among them, the chlorination method is the most common, because chlorine has strong disinfection ability, is cheap, the equipment is simple, and the residual chlorine determination is convenient; It is easy to increase the amount and adjust it and is widely used. In addition to the use of chlorine, there are also chlorine compounds, such as sodium hypochlorite, calcium hypochlorite, chloramines and chlorine dioxide, which has been widely used in waterworks abroad recently - this is an oxidant with stronger oxidizing properties than chlorine. Non-oxidizing biocides such as chlorophenol disinfectants and quaternary ammonium salts can also be used for disinfection.

Recently, methylene dithiocyanate, dodecylguanidine hydrochloride, organic bromide, etc., as well as NL-4 and SQ8, which have been successfully developed in China, are all effective disinfectants. In addition, copper salts, such as copper sulfate and other biocides, were used in the early days, which are all chemical methods of disinfection.

When the water is heated, chlorine can be released from the water.

There are a lot of bacteria in raw water.

1.Because the chlorine in tap water can interact with the remaining organic matter in the unboiled water, the risk of bladder cancer and rectal cancer increases. Boiling water for 3 minutes can evaporate the chlorine and some harmful substances in the water, and at the same time retain the essential nutrients in the water.

2.There are bacteria in raw water, and drinking raw water is easy to contract diseases.

3.Industrial wastewater, waste residues, pesticides and other chemicals can cause water pollution.

I think ah! There must be bacteria in this water! And a lot of it? But bacteria are also life, we don't need to kill them all!

It must be mainly osmotic water absorption.

Osmosis is the way in which water molecules (or other solvent molecules) pass through a semipermeable membrane from a high to a low concentration.

Here, the cell membrane of bacteria is equivalent to a semi-permeable membrane, just like the cell membrane of animal cells, and like the protoplasmic layer of plants, they are all semi-permeable membranes, so the entry and exit of water molecules into and out of the cell belong to osmosis. In a hypertonic solution, bacteria will also lose water through osmosis like animal cells, for example, cured bacon can be sterilized.

The swelling and water absorption is mainly for some cells like dry seed cells and meristem cells, the cytoplasm is particularly concentrated, containing a large number of hydrophilic substances, such as protein, starch, etc., and has a strong ability to absorb water, so the water absorption of such cells mainly depends on swelling and water absorption.

Cellular metabolism consumes very little water, and in many cases produces water, such as bacteria, parasites can survive in sun-dried seeds, it is metabolism that produces a large amount of water.

Hope it works for you!

Water is a small molecule substance that can pass freely through the cell membrane and cell wall of bacteria, so the way water enters bacteria is free diffusion.

There are many substances in bacteria, and the osmotic pressure is very high, so it is osmotic and absorbs water.

Seed germination is swelling and water absorption.

Metabolic water absorption is the process of using the energy released by respiration to allow water to pass through the plasma membrane and enter the cell.

I don't know, you can check it yourself.

Summary. Extended information: According to the national standard, the multi-tube fermentation method is divided into three steps: primary fermentation, plate separation and fermentation.

In practical work, in order to save time, some comrades proposed to check the table directly after the initial fermentation, that is, the last two steps were omitted to determine the experiment. In order to verify the feasibility and accuracy of the simplified method, multiple sets of experiments were carried out for different types of water samples, and from the experimental results, in principle, the more complex water samples such as hospital wastewater and domestic sewage should be completed after the two-step experiment, which cannot be simplified. Although in most cases, the test tube of the initial fermentation of acid and gas production is verified to be positive for coliform bacteria, but there are also some hospital wastewater and production sewage water samples that have negative coliform bacteria reaction when the plate separation is verified, so at least the plate separation should be done when the time is tight, because a large number of experiments have proved that the consistency rate between the results of the first two steps and the results of the three-step method can reach 92%.

Okay, what are the two specific questions you would like to ask?

It was after this experiment that I had some problems.

Hello, the problems in the bacteriological detection experiment of water quality are: 1. The glassware used in the test should be borosilicate glass products, and the wall of the test tube should be thicker than the common chemical test tube, so that it is not easy to be damaged during operation. 2. In order to collect the gas produced by coliform bacteria fermenting lactose, it is necessary to branch and invert the De Han's blind tube. When the blind tube is first put into the culture medium, there will be a small amount of air in the tube that cannot be discharged, but after high temperature and autoclaving, the air in the tube will be discharged, and the inside will be filled with the culture medium

3. The inoculation tool is mainly sold orange is the inoculation ring, if there is no special inoculation ring, it can be made by homemade, generally can be bent by platinum wire or nickel wire, thicker electric furnace wire can also be, bent into a small ring should not be too big, otherwise it is not easy to pick up colonies.

Extended information: According to the national standard, the multi-tube fermentation method is divided into three steps: primary fermentation, plate separation and fermentation. In order to save time, some comrades proposed to check the table directly after the initial fermentation, that is, the last two steps were omitted to determine the experiment.

In order to verify the feasibility and accuracy of the simplified method, multiple sets of experiments were carried out for different types of water samples, and from the experimental results, in principle, the more complex water samples such as hospital wastewater and domestic sewage should be completed after the two-step experiment, which cannot be simplified. Although in most cases, the test tube of the initial fermentation acid and gas production has been verified to be positive for coliforms, but there are also some hospital wastewater and production sewage water samples that call for a negative reaction of coliform bacteria when the plate is highly blind and blind separation verification, so at least the plate separation should be done when the time is tight, because a large number of experiments have proved that the consistency rate between the results of the first two steps and the results of the three-step method can reach 92%.