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At present, the main process used in the sewage treatment plant is basically the activated sludge method, the best way to measure its operating function is good or bad, the best way to judge the development trend is to analyze the activated sludge microorganisms, this article analyzes and expounds from the process of microbial microscopy and its indicative significance, so that we can understand the knowledge of microbial microscopy in sewage treatment and apply it to practice.
<h1>01 Microscopic process analysis</h1>
(1) Sample collection and counting
The impact of sample collection on the microscope observation effect is more obvious, only the collection of the appropriate position of the sludge mixture can make an accurate judgment and analysis, in practice we generally select the most representative sampling location of the microbial population - the end of the aeration tank (outlet), in addition, the sludge at this point has the characteristics of good stability and good flocculation.
After collecting the mixture to be measured, pay attention to avoid precipitation, should be placed under the microscope as soon as possible to observe, the specific process is: the mixture to be measured to take a small amount in the beaker (before taking the need for slight stirring, to avoid flocculation precipitation), and then use a rubber head pipette to aspirate the liquid to be tested in the middle of the mixture, squeeze out a few drops, drop a drop in the central position of the slide, then gently cover it with a coverslip, and finally use filter paper to aspirate the excess part around the coverslip and place it under the microscope for observation.
Due to the aspirate a drop of activated sludge mixture. After wiping, the remaining remaining is only 3/4 drops, and each ml of activated sludge mixture can drip out 24 drops, so the actual volume of extraction is 0.75mL/24=0.03mL, and the number of microorganisms can be calculated to be the number of corresponding protozoa and epizoans contained in the sludge mixture per milliliter.
(2) Microscope adjustment and observation
When using a microscope to observe the sample to be measured, be sure to make sure that the coverslips and slides are wiped clean, and there are no stains or water droplets on the surface to prevent interference. Regarding the choice of microscope, monocular or binocular lenses can be used, and the magnification can reach 800 to basically meet the needs, because most protozoans can see when magnified 100 times, magnified to 400, 600 or 800 times, you can see its cilia, antennae or shrinking bubbles and other structures.
In the observation process, first of all, to adjust the coarse magnoccal spiral, after finding the bacterial glue group, and then adjust the fine pulfocal spiral knob, according to the field of view from left to right, from top to bottom observation, when the characteristic microorganisms are found, and then switch the objective lens magnification for magnification observation, while making a record, the observation period mainly observes the following aspects: the morphology of the bacterial gel group, color, loose tightness; microbial species, population, quantity, etc.
<h1>02 Microbial species and representative significance</h1>
(1) Protozoa
In protozoa practice, there are generally three categories, namely non-activated sludge, intermediate activated sludge and activated sludge.
(1) Non-activated sludge protozoa: Such protozoa often appear in large numbers and develop into dominant population microorganisms when the activated sludge system fails and the parameters of various control projects are not controlled reasonably. The following is a map of the common non-activated sludge protozoa in sewage treatment and its indication significance.
Bodou worms
Side-jumping trichomoniasis
Bean worms
Dark-tailed filarial worm
Nephroplastia
Twisting the head worm
(2) Intermediate activated sludge microorganisms: slow swimming type as the main feature, in the initial stage of activated sludge bacterium to the maturity stage of activated sludge appear. The following is a map of the common non-activated sludge protozoa in sewage treatment and its indication significance.
Cowardly tube leafworm, small in size, with cilia around the body, half of the body size, swimming rapidly, shuttling through the inside of the fungal gel group.
The schizoite ( also known as the long-necked worm ) is about four times larger than the cowardly tube leaf worm , has cilia around the body, swims slower than the cowardly tube leaf worm , and has low mobility.
Oblique tubeworm, 800 times clearly recognizable. The body is soft, swims faster, and moves outside the gum mass.
Bag whipworm: the body is stationary, the change is larger, there is no certain form, and the action is always longitudinal. Occurs when the BOD load is low and the DO concentration is high.
Intracultural canal worms: oval, two equally elongated flagella, one sliding and one dragging, appearing indicating a lower treated water BOD.
Roaming insects: comparable in size to schizopters, with a neck that is 1/3,400 times the body length, and are more commonly seen during the transition from deterioration to recovery of sludge.
(3) Activated sludge protozoa: there are more species, more frequent occurrence in sewage treatment microscopy, the most reference value for the judgment of sludge activity, its number, how many types are also the measurement of sludge live performance, mainly divided into two categories, swimming ciliates and attached ciliates. The following is a map of the common non-activated sludge protozoa in sewage treatment and its indication significance. (This type of protozoa combined map is easier to identify, no longer attached here)
Bell worms: sludge or good sex, free bacteria balance, less toxicity, inert substances;
Mormon worm: after the optimal period, tends to disintegrate and low load state, SS increased slightly;
Tired branches: a little after a good period, the key to measuring the disintegration of urban sewage sludge;
Straw worms: slightly past the good stage, tending to appear before and after disintegration;
Monoclonal: appears when the water quality is treated well, and the situation of polycondensal insects is similar;
Cover fibrella: the treatment water quality tends to be good, and the proportion of fecal sewage is high, and it appears in large quantities;
Wandering worms: appear when the mud is old or has disintegrated, and can also be seen when the DO is low;
Shield fibrella: the sludge is in good condition to the disintegration stage, appears when the DO is high, and is sensitive to DO;
Ferrets: low load, sludge disintegration is more than the number of rotifers;
Echinococcus: high load tends to improve or disintegration occurs, and the number is not large.
(2) Epizoans
The epizoans are more advanced than the protozoa, the body size and mobility are stronger than the protozoa, clearly identifiable at 400 times, mostly feed on the fungal gel group, and the activated sludge appears in a small amount in the normal state. Common prozoan categories and their indicative significance are enumerated below:
Saddle beetles
Chalcedropodium
Spiny worms
nematode
Ladybirds
Bearworms
water flea
Epizoans will appear in large quantities when the sludge is aging, and rarely under normal conditions, because their feeding objects are small free fungal micelles, and the sedimentation performance of the sludge is poor at this time, the supernatant is slightly turbid, and there are fine particles suspended. Of course, epizoans also have some indicative effects: rotifers show a positive effect on activated sludge, while saddle beetles and hornworms show negative effects; when sludge aging enters an accelerated period, the number of nematodes, ladybirds, and fairy worms will increase significantly.
<h1>03 Microscopic sludge activity and process parameter analysis</h1>
（1）SV
Excessive load: the supernatant is turbid, the sludge settlement limit is not obvious, at this time, microscopic inactive protozoa are dominant, there are more side jumpers and trichomoniasis, and the F/M value is comprehensively analyzed.
Sludge aging: the supernatant is clear and mixed with fine particles, the number of microscopic rotifers is large or the appearance of epidermal worms, etc., there are almost no inactive species, and then combined with the F/M value to judge.
Over-aeration: activated sludge suspended in the graduated cylinder, supernatant and lower clear liquid, microscopic examination of inactive protozoa dominant, adhesion protozoa activity weakened or overhead bubbles, and then calculate F/M and the ANALYSIS of the DO situation at that time.
(2)ALL
High SVI: When the SVI value exceeds 150, it is necessary to observe whether the number of filamentous bacteria increases with the help of microscopic analysis, and the inactive protozoa increases, and the F/M value is higher, which can basically be judged as sludge expansion (excluding excessive aeration).
Low SVI: long-term low may be related to sludge aging, short-term low may be sludge death or excessive discharge, if the sludge death may be toxic substances in the inlet water, at this time microscopic examination will find that the number of protozoa sharply reduced or disappeared; if the sludge is excessive, it is manifested as a small bacterial gel mass, light color, and intermediate protozoa dominant.
Sludge reflux ratio: the reflux ratio is too large, the actual residence time of sludge in the biochemical system is shortened, and the biological phase will show that the bacterial glue mass is fine in color, the luster is light, and the inactive class is dominant; the reflux ratio is too small, the corresponding activated sludge stays in the biochemical pool for a long time, and microscopic examination will find that a large number of epizoans appear and the inactive class is reduced.
Practical guidance for several microorganisms
<h1>04 Epilogue</h1>
Microbial microscopy is a basic skill of operation technicians, only to do a good job of daily microbial microscopic analysis, combined with sludge settlement performance, sludge concentration, HRT, mud age, sludge load, DO, reflux ratio and other parameters to make a comprehensive analysis and judgment of the biological system, it is conducive to our daily operation and management of sewage. By understanding the operating conditions of the biological pool, the process parameters are adjusted in time to ensure the stable operation of the entire system, and then achieve the ideal effluent quality.