Introduction

05.10 case analysis of Hunan customers' reaction to reagent failure:Huaihua, Hunan Province, is a low mountain and hilly area. The waste incineration power plant needs a lot of clean water for normal p…

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05.10 case analysis of Hunan customers' reaction to reagent failure:

Huaihua, Hunan Province, is a low mountain and hilly area. The waste incineration power plant needs a lot of clean water for normal production. The enterprise itself quotes the river water for simple treatment and then enters the production for use.

The reason for more rain in recent summer is that the water quality is relatively turbid and does not react and flocculate after adding polyaluminium chloride. If the dosage of medicine is increased, it still has no effect. Is the medicine invalid or what is the reason? If the turbidity is high, increase the dosage, but now it turns yellow when added to the water, there is still no reaction.

First of all, ask the customer what kind of water is treated, what kind of treatment process is used on site, what kind of reagent is used, whether there is any change in the recent process flow, whether the pH value of the influent has changed, and whether the change in a small range of influent temperature will not be affected.

There are several reasons for non precipitation, as follows:

1. PH value. PAC can react only in the pH range of 6-9. Under normal circumstances, most water quality is neutral, and some water quality is acidic or alkaline. In this case, it is recommended to carry out acid-base neutralization in advance, such as adding lime or flake alkali, hydrochloric acid, etc., and adjust it to the range of 6-9.

2. Low temperature and low turbidity. In case of some low-temperature or low turbidity water quality, conventional PAC is difficult to react. At this time, spray polyaluminum chloride can be selected with low basicity, which has good effect for such water quality. For sewage with high turbidity, polyaluminium with low content of mixed slurry can be selected, because the water-insoluble matter in it can be used as stowage to improve the flocculation and sedimentation effect.

3. Dosage problem. Although polyaluminium chloride has a good effect on sewage treatment, it does not mean that the greater the dosage, the better the effect. This idea is wrong. No matter what kind of sewage quality, PAC has a reasonable dosage in actual treatment. If the dosage is too large or too small, it will cause no reaction, no sedimentation and no flocculation.

4. The problem of the medicine itself. The principle of sewage treatment is to flocculate the suspended solids or impurities in sewage into a mass. When using some products with poor or unqualified quality, the flocculation speed is slow and there are many water-insoluble substances, resulting in small vanadium flowers, suspended in sewage and no settlement.

Now we need to take a bucket of water sample and go to the laboratory for a beaker test to find the cause of the problem.

In addition to the basic beakers and utensils in the laboratory, the following items need to be prepared:

1. Dissolved PAC 10% aqueous solution

2. Dissolved PAM 1 / 1000 aqueous solution

3. PH test paper: lime, flake alkali or liquid alkali used to adjust pH value

Beaker test process

Step 1: measure the pH value of raw water, add lime or sodium hydroxide liquid if it is lower than 7, and adjust the pH value of water body to 8.

Step 2: one milliliter, one milliliter, gradually add polyaluminium liquid. When stirring, stir in one direction for two minutes. If alum appears in the water body, the addition of PAC can be stopped if there is flocculation. Remember how many milliliters of PAC were added. Then add anionic PAM liquid to help sedimentation to see the effect. (PAM can be added directly without further decolorization)

Step 3: after adjusting the pH value of raw water, fill 3 ~ 4 beakers respectively. According to the dosage value just obtained, add a few milliliters of PAC to start flocculation, and fine tune the reduction and increment respectively to determine the optimal dosage.

The customer has determined for many times that the pH value measured before is neutral above 7. During the experiment, it is found that the pH value of the influent is only 6.3. It is because of the recent heavy rainfall, the rainwater itself is weakly acidic, and the humic plants on the mountain are also acidic, so the river water quality becomes weakly acidic. PAC failed to play its due role, but the flocculation effect was significantly improved after the pH value was adjusted to weak alkalinity.

terms of settlement:

Add hydrated lime water at the water inlet or before PAC dosing port. On the one hand, it can play the role of physical precipitation, sterilization and disinfection, and on the other hand, it can adjust the pH value of sewage. (be sure to ask about the later use of sewage. Lime powder has low cost, but it is easy to precipitate calcium carbonate. There are also those with liquid alkali, that is, sodium hydroxide, but the cost is much higher than lime powder.)