21 questions on Coagulation and sedimentation process and flocculant selection in sewage treatment

Coagulation is the general name of coagulation and flocculation.

Flocculation means that when a small amount of polymer is added to the sewage, the polymer molecules are rapidly adsorbed and combined on the surface of colloidal particles, and a polymer chain can absorb multiple colloidal particles at the same time. Each particle depends on the polymer connection to form some kind of aggregate or combine into flocs and precipitate and separate.

In fact, the two are not separate in the process of sewage coagulation treatment.

Ask1

At present, a test of pickling and phosphating wastewater has been done, and the specific process is as follows. Process introduction: the production sewage produced in the production process is first treated by the regulating pool, then flows into the reaction pool through the lifting pump, and lime water is added to the reaction pool (Ca(OH)2) to adjust thepHValue in9.5~10.5Then the water enters the coagulation reaction pool and coagulant aids are added to the coagulation so that the pollutants in the wastewater exist in a larger particle state in a suitable acid-base environment and have good sedimentation performance.

The solid-liquid separation of the wastewater is carried out effectively through the inclined tube sedimentation tank, and the wastewater treated by the sedimentation tank is adjusted into the neutralization tank.pHValue to6~9The discharge is up to the standard after being discharged into the sand filter for advanced treatment. The sludge of the sedimentation tank is pressed into the sludge concentration tank by the sludge pipe and cleaned regularly after being pressed by the filter press. 

pHLime water and lime water are used to adjust the value.H2SO4Polyacrylamide is used as coagulant(PAM). Water intakeCOD1800, effluentCODYes450Cannot be reached110The first-level standard. 

If you want to ask, this kind of waste water needs to be added.PACFlocculation? Need, it'spHHow much is the value controlled? At present, if we want to meet the standards, how can we improve them? Can the waste water be used for reuse? Will the reuse of the ions in it affect the product? What criteria should be met for reuse?

A:There is nothing wrong with the workmanship. To addPACOtherwise, the floc is too small and the effect is not good.pHThe value should not be lower than8.5The effect of phosphorus removal is better.

Ask2

The leading products at this stage include3-Chlorine-4-Fluoroaniline,3-Chlorine-4-Fluoronitrobenzene,2-Fluorine-3-Chloronitrobenzene, daily treatment of water30---38T/d，pHMeasured with test paper, the inaccurate treatment process is as follows:A/OLaw.

Raw water (pHFor5---6)-Electrolytic cell (28(cubic meter)-neutralize the storm tank (without lime for a long time)pHFor6.5Left and right)-filter press-water quality adjustment pool (pHFor6---6.5)-anaerobic tank (pHFor6.5Left and right, self-flowing into the aerobic pool, long3.5Meter, width3Meter, effective water depth3Rice. The color is yellow and transparent. After the measuring cylinder is taken for a long time, the color becomes darker, not yellow)-- aerobic tank (pHFor7.5Self-flow to the secondary sedimentation tank2A pool1The pool is reserved for2No. Ikei2No. IkeiSVRatio1The pool is small, each long8.5, wide4Meter, effective water depth3Rice, the color is a little dark, taupe. The filter paper is filtered, the color is similar to that of the anaerobic tank, and the filter paper remains grayish black.2No. 1 aerobic tank self-flow to) secondary sedimentation tank (sludge reflux to aerobic tank or anaerobic tank or neutralization burst tank)-current water quality adjustment tank of outlet tankCOD1000-1400(lower than before), out of water400-700Left and right biochemistry1Number poolSV:4%I would like to increase, the current influent concentration is lower than before, before throwing trisodium phosphate for a week, there is no effect ah? I filter the effluent with filter paper, and the color is similar to that of the anaerobic tank. The residual black on the filter paper should be excessive anger, and the mud has been broken. ), it used to be morning7Point15And afternoon17Separate points into the water3Hours, separate aeration8Hours.

Now I want to adjust and get water at once in the morning.5Hours, into the water after the gas for eight hours, while throwing industrial glucose or starch, urea, trisodium phosphate, trisodium phosphate, before a week of trisodium phosphate no effect ah, considering the biochemical property is not too bad? Residence time of anaerobic tank24Hours. How about this? When is the right time to add it? Add it as soon as the water comes in? Add it after you get the water? Or? Is it added directly to the anaerobic tank at the beginning or to the anaerobic tank and aeration tank respectively after entering the water?

A:

1The biodegradability of waste water is not high, it can be tested specifically.B/CBy contrast, this test is still very necessary. if you cannot test it yourself, entrust an external testing agency to test it.

2I think it's very low, and if it's tested, it needs to be tested.2One sample is raw water and the other is waste water entering the aerobic tank.

3At present, the situation of the aerobic tank you mentioned is mainly caused by the entry of refractory organic matter into the biochemical pool. Please extend the residence time of the waste water in the anaerobic tank.

4The addition of trisodium phosphate does not increase the substrate concentration, so if it is not necessary to add nitrogen and phosphorus, the easiest way is to detect whether the content of nitrogen and phosphorus in the water is close.1Class II emission standards are fine.

5The addition of starch should be able to submit the sludge activity, but the investment is relatively large and it is not suitable for long-term addition. If you want to add, put it in the body of water that enters the aerobic pool.

Question 3

At present, I have come into contact with a kind of wastewater: the main components of the wastewater are aniline, cyclohexylamine, and some benzene by-product resins and so on. During the physicochemical treatment, the wastewater is very clear and transparent after flocculation and sedimentation.pHContinue to increase to14In the process, there is no sediment. And then after biochemistry, the regulationpHLater, there are a lot of flocs, at this time.pHValue in11About, my suspicion is that there are alkali-soluble substances in the waste water, and after biochemistry, the modification is precipitated under alkaline conditions. I don't know if it makes sense. Part of the domestic sewage mixed into the wastewater has been investigated, and it is not found that there are precipitated calcium and other substances in the water under alkaline conditions. Another is that this kind of water is added in the process of biochemical and flocculation.PAC，PAMAnd calcium hydroxide, it was found that the surface of the sedimentation tank was white, as if there was fog in the water. I don't know if it's lime. Stop adding lime is still the case, I do not know what is going on? Is it the role of precipitated calcium hydroxide from the undischarged mud at the bottom of the sedimentation tank?

A:Effluent of biochemical systemSSIt is not low, so addPAC、PAMCaused by the formation of flocs after the formation of activated sludgePAC、PAMAfter flocculation, the floc is easy to include air bubbles and form scum, which may be related to the liquid level of the sedimentation tank.

Question 4

What we use isSBRIn the process, the sewage has a flocculation sedimentation process before entering the biochemical pool, adding polyaluminum ferric chloride and polyaluminum chloride.PAM. I always think that this operation will have an impact on the activated sludge, because the chlorine content in the raw water itself is on the high side.SSIn300Wouldn't the chlorine be higher after coagulation? Is it necessary to do so?

Answer: what has an impact on microorganisms is free chlorine, polyaluminum ferric chloride, which will not produce favorable chlorine. Don't worry, it's right to enter the biochemical system and carry out physical and chemical pretreatment.

Question 5

Why does the waste water enter into the biological after chemical addition?CODWill be better than facultative oxygen+Aerobic effluentCODLow??Under what conditions will this happen?

A:First of all, we need to know that microbes are also organic matter, which can also causeCODRise, that is to say, if the effluent contains more microbial flocs, the measured waste waterCODIt'll be taller.

Question 6

Due to the low influent concentration, we also add flour and urea. AddPAMDoes it have any effect on sludge reflux??If you don't addPAMIs it good to let the aged sludge be taken away with the water?

A:

1, plusPAMIt's bad for the biochemical system.

2The outflow of aging sludge has no effect on the system, on the one hand, it is also passive to deal with the low load, so the normal protection state.

Question 7

Effluent after air floatationCODInstead, it went up, adding medicine to poly aluminum.200mg/tHey, is there too much medicine?

A:Polyaluminum chloride is an inorganic flocculant, and adding too much medicine will not lead to effluent.CODIf it goes up, see if there is any problem in other aspects. For example, the flocculation effect is not good (the capture of colloid is not enough) and so on.

Question 8

Do you have any high performance ones?PAC(dye that can remove the fluorescent effect) basic aluminum chloride and polyaluminum chloride were used to have no effect on it at all.~~There is a lot of thin worms growing in the anaerobic pool after the annual leave, what is the reason? Is it a big problem?

A:

1For dyes with fluorescent effect, the effect of coagulation and sedimentation is not very good.

2The emergence of metazoan in the anaerobic pool is not a big problem. After the recovery of water and the stability of the system, there will be some improvement. This kind of protozoa cannot survive in pure anaerobic condition.

Question 9

I am now debugging is brightener wastewater, our process is physical and chemical.+AOOur materialization is to adoptfentonOxidation, we adjust it with sulfuric acid.pHA large amount of sulfate and some ferrous ions enter the anoxic pool, and the hydrogen sulfide and ferrous ion produced make it black and stink, affecting the treatment effect. How to adjust?

A:Whether it can be removed by adding calcium hydroxide and then coagulation and sedimentation.

Ask 10

The heavy metal wastewater of our company is treated by physical and chemical treatment, and the daily treatment capacity is100tThe process is as follows: neutralization-coagulation-flocculation-vertical flow precipitation-secondary reaction pool-inclined tube precipitation, water quality before treatment: total silver ≤2.6mg/L, total cadmium ≤800mg/L, total nickel ≤800mg/L, total zinc ≤300mg/L, total copper ≤1000mg/LThe treated water quality cadmium seriously exceeded the standard, neutralizer tried sodium sulfide, sodium hydroxide, lime, coagulant tested polyferric sulfate,PACBut it always exceeds the standard.

A:The concentration is relatively high.

1Please use calcium hydroxide and ferric chloride to neutralize.

2Use of ferric trichloride in coagulation+PAMIf the concentration is too high, the effluent is retreated to dilute the concentration of the raw water.

Ask 11

After debugging, a cleaning waste water (factory that produces valves)7T/D, mainlyCODAnd petroleum.COD=1500-2000, petroleum=900，pH=7-7.5, requirementsCOD≤100Petroleum ≤5The process is gravity oil separation-Regulating pool-Reaction cell1-Reaction cell2-Carbon filter-Effluent, reaction tank1Add lime,PAC、PAM. Reaction cell2ForFentonReaction is added firstH2SO4, adjustpHTo3Add to the left and right.FeSO4AndH2O2Reaction for one hour, neutralization with lime and final addition.PAMThere is a super foam reaction tank in flocculation commissioning.2MediumFentonFlocculation and precipitation will always float up after the reaction.

A:Mainly in the ratio of hydrogen peroxide to ferrous sulfate, you can use different proportions in the laboratory to see the effect and foam.

Question 12

At present, the biochemical effluent is flocculated directly, and the drug has been added before the secondary sedimentation tank, and the drug can not be stopped, but also to return, can only return the flocculated sludge, itself is industrial wastewater, the sludge production is very small.b/cFail to reach0.1. 

A:Based on the poor effect of your biochemical treatment, it is understandable to add flocculant. At this stage, if you can ensure that the effluent is qualified, it is also possible. Wait for the follow-up load or biodegradability to come up, and then change the dosage situation.

Ask 13

What is the function of adding diatomite and polyaluminum chloride during the commissioning of sewage treatment? The aerobic tank needs to discharge excess sludge. After sedimentation, should the sludge be discharged first or drained first? Is there air floatation in the aeration process of aerobic tank?

A:

1These agents are generally used in the stage of physicochemical treatment, not in biochemical treatment, and their function is to improve the effect of coagulation and sedimentation.

2It can be drained first and then discharged mud, or at the same time. No strict requirements.

3There is no need for air floatation, nor can it be floated.

Question 14

I would like to ask what kind of agent can be used to precipitate the electroplated degreasing and degreasing wastewater?

A:Can be demulsified with calcium chloride, adjusted by calcium hydroxidepH(8.5Left and right), then ferric trichloride+PAMThat's it.

Ask 15

Aluminum foil wastewater, using calcium hydroxide+PAMCoagulation and sedimentationpHControl in8~9The treated water is clear and free of precipitation, but with a little green, and a white suspended substance will be formed after a few hours. I don't know why. For aluminum foil wastewater, what kind of medicine should be used for the best coagulation effect?

Answer:Please confirm the precipitated waterpHChanges in values, especiallypHControl in8~9After, whether it has been adjusted againpHWorth it? Your use of calcium hydroxide+PAMThere is no problem with the coagulation and sedimentation process, and the medicament is matched.OK. The problem you mentioned mainly lies in the craftsmanshippHControl and influent quality.

Question 16

I did a small test of coagulation and sedimentation today, and the effect was not good. The details are as follows: the waste water is the waste liquid of sulfuric acid washing soap feet, the specific composition has not been detected, the waste water is dark red and clear, and the suspended solid is not high.COD:10-14Ten thousandpH:0.5-3. The first small test: add an appropriate amount of calcium hydroxide (a large amount) to the original solution.pHAdjust to8-9After that, polyaluminum chloride was added to precipitate after flocculation, and the color of the supernatant was relatively clear, and the color was removed according to the target measurement.80%Left and right, precipitation1The sediment accounts for the total water after an hour.60%Around, the slag production is too high. The same regulation of calcium hydroxidepHTo8-9Polyacrylamide was used as flocculant, and the basic raw liquid did not change. And choose to adopt regulation.pH8-9After adding polyaluminum, stirring and adding polypropylene, the sample becomes turbid and milky.

The second small test: add an appropriate amount of sodium hydroxide to the original solution (the same amount is very large), and set thepHTuned to8-9After that, the same as the above three coagulation methods, the results are not ideal. 

Would you like to ask, do you need some special conditions, or is there any other way? Undetected water quality components, mainly some dissolved substances, colloid is very few. I feel that the main substances are sulfuric acid, chlorate, dissolved oil, phosphorus, glycerol and so on.

A:Considering the problem of producing slag, we can choose sodium hydroxide to adjust.pH. AddPACAdd it later.PAMYou can try different modelsPAM, negative or positive. The concentration can also be relaxed, and since it is a small test, it is necessary to conduct multiple tests. In addition, the operation method should also be well controlled, such as mixing time, intensity and addition.PACPost-additionPAMThe timing and so on.

Question 17

The flocculation effect is OK, but it is after flocculation.CODThe loss is great, but the ammonia nitrogen does not change, which leads to the serious imbalance of carbon-nitrogen ratio, and the subsequent biochemistry can not be done without replenishing the carbon source. What about this situation?

A:Low load is fine for ammonia nitrogen removal, but carbon source is needed if total nitrogen removal is required. In this way, you can get the right biochemistry by controlling the proportion of drugs.CODValue, so that under control, the effect will be more important.

Ask 18

Is there a reaction tank in front of the coagulation sedimentation tank? We added a small amount of medicine. After stirring and dissolving, can you throw it directly into the pipe?

A:Can replace the reaction pool, but the flocculation pool had better, after the formation of flocs and then go to the sedimentation tank precipitation, so that the precipitation effect is better, if not, the effect is worse.

Question 19

Printing and dyeing wastewater, physicochemical plus hydrolysis, contact oxidation. Physicochemical addition of ferrous and lime. A large amount of chemical sludge and biochemical sludge are produced every day, adding cations.PAMDewatering with a belt mud press.1Physical and chemical sludge is better than biochemical sludge in dewatering.2The physical and chemical sludge is usually positive, and the effect of adding flocculant is good.3Easy to add relative to that kind of sludge consumptionPAMWill it be higher?

A:

1The physical and chemical dewatering is good, on the one hand, because the physicochemical sludge has a skeleton and is easy to form a floc core.

2, unit dosage ratio, biochemical sludge consumptionPAMObviously more than materialized.

3. In addition, it is suggested that sodium hydroxide can be added instead of lime without affecting the removal rate, and the sludge production may be greatly reduced.

Ask 20

What I treat is printing and dyeing wastewater, and the treatment process is adjusted.+Air flotation+Hydrolyze+Contact oxidation+Materialization+Sand filtration, the effluent after sand filtration was originally planned to be used for printing and dyeing. In the selection of air floatation agents and post-physicochemical agents, I just started to use aluminum sulfate for air flotation (adjusted with lime before adding.pHValue), for post-materializationPAC+PAMA combination. Aluminum sulfate does not seem to be very effective in the application of air floatation, and other agents are being considered. So I'd like to ask you about the choice of air floatation and post-physicochemical agents.PAC, aluminum sulfate, polyaluminum ferric chloride and other types of agents, which can decolorize and remove printing and dyeing wastewater.SSBetter, and more suitable for air floatation.

A:This does not have much experience, however, do not need decolorant, only use flocculant, whether to achieve the effect is still uncertain. In comparison, the combined addition is better than the single addition, but in addition to what flocculant is added, the proportion is also very important, so it is necessary to determine what flocculant and dosage through the cup bottle experiment.

Ask 21.

Lime can be decolorized and removed.CODIs it? As ferrous sulfate is now used as a coagulant, there is a lot of sludge in the sedimentation tank. I want to add one more filter press. I don't know which one is better.(Now we use a diaphragm pump to suck mud. I feel a little inefficient. Please recommend it. There is also the problem of hexavalent chromium.PH3Can it be removed by adding ferrous iron? Leather printing and dyeing wastewater to which kind of agent to reduceCODThe effect is good.?

Answer:

1Quicklime has a certain decolorizing effect.CODThe removal effect is general, and the solubility can not be removed.

2The combination of diaphragm pump and plate and frame pressure filtration is relatively common.

3Hexavalent chromium, if reducedPH3It is necessary to reduce and then coagulate.

4Sludge can be dewatered and then dried in the sun, which can reduce the weight of sludge.