Environmental protection water treatment

What are the reasons for the stability of colloid that can exist in water?

(1) The surface of the colloid is charged;

(2) There is a water level on the surface of the colloid;

(3) The surface of the colloid absorbs some substances that promote the stability of the colloid.

What is the purpose of using coagulants?

1) Improve the structure of the floc, make its particles grow, strong and heavy;

2) Adjust the PH value and alkalinity of the treated water to achieve the best coagulation conditions and improve the coagulation effect; Coagulants themselves do not coagulate, but can promote the coagulation process of impurities in water.

 the basic concept of coagulation?

Because the colloidal particles in the water are negatively charged, they repel each other, and at the same time, they continue to do "brown motion" in the water is extremely stable, not easy to sink, when the right amount of coagulant is added, the tiny colloidal particles in the water can be destabilized, resulting in adsorption bridging, flocculation into flocculent rapidly sinking, this process is called coagulation.

What are the main factors affecting the coagulation effect?

1) PH of water: such as the hydrolysis of PAC to produce Al(OH)3 colloid, when the PH is 6.5-7.5 the smallest dissolution, coagulation effect is good;

2) alkalinity of water: When the alkalinity is insufficient, the coagulant continuously produces H+ in the hydrolysis process, which decreases the PH value and the coagulation effect;

3) Water temperature: when the temperature is low, the viscosity of water is large, the hydrolysis rate is slow, the formation of floc is slow, and the structure is loose, and the particles are small and not easy to precipitate;

4) The composition of impurities in water: the nature and concentration have a great impact on the coagulation effect.

What is the relationship between the form of carbonic acid in water and PH?

1) When PH value ≤4.3, only CO2(free) in water;

2) When PH value =8.3-3.4, more than 98% are HCO3-;

3) When PH >8.4, there is no CO2 in the water

 the purpose of boiler water treatment?

1) Prevent the accumulation of sediment and corrosion of water and steam in the operation of the boiler body and affiliated systems. Improve the heat transfer efficiency of boiler.

2) Ensure steam quality, prevent scaling and corrosion of turbine components, reduce boiler blowdown losses and improve economic benefits under the condition of ensuring water quality

the working principle of centrifugal pump?

Centrifugal pump is the use of impeller rotation to produce centrifugal force water to work, the pump before starting, must pump shell and suction pipe are full of water, and then start the motor, so that the pump shaft drive impeller and water for high-speed rotating motion, water under the action of centrifugal force thrown to the outer edge of the impeller, and collected into the pump shell, through the flow channel of the vortex pump shell into the pressure water pipe.

At the same time, the center of the impeller of the pump forms a vacuum because the water is thrown out, and the water in the suction pool is sucked into the impeller through the suction pipe under the action of atmospheric pressure. The impeller keeps rotating, and the water is constantly thrown out and constantly replenished. This creates a continuous flow of water from the centrifugal pump.

 What is the regeneration of resin?

After softening or desalting, the resin loses the ability to exchange ions. At this time, acid, alkali or salt can be used to reduce and regenerate it to restore its exchange ability, and this process of restoring the ability of the resin is called the regeneration of the resin.

 What are the main factors affecting the resin work exchange capacity?

(1) the quality of water in the influent;

(2) Control index of exchange end point;

(3) the height of resin layer;

(4) Water temperature and flow speed;

(5) The effect of exchanger regeneration and the performance of the resin itself.

What are the chemical properties of resin?

1) Reversibility of ion exchange reactions, such as:

RH+Na+RNa+H+

2) Acid-base:

ROHR+OH-; RHR+H+

3) Selectivity: The adsorption of different ions by ion-exchange resins is not the same.

4) Resin exchange capacity

Positive resin

Fe3+>Al3+>Ca2+>Mg2+>K+≈NH4+>Na+

Negative resin:

SO42->NO3->Cl->HCO3->HSi

What is the pollution of mixed bed resin?

1) Suspended pollution: mostly in the form of Yang resin. Strengthen the pretreatment of raw water.

2) Organic pollution: mainly occurs in strong alkali Yang resin. Main resuscitation methods: Soak the resin in a mixture of NaOH(1-4%) and NaCl(5-12%) for 24 hours.

3) Heavy metal ion iron pollution: mostly formed in negative resin, strengthen the corrosion of pipes and equipment, reduce the Fe content of water, and increase iron removal measures.

 What are the main reasons for the deterioration of RO film performance?

1) Chemical changes of the film itself: hydrolysis of the film, free chlorine, and oxidation interference of active chlorine

2) The physical changes of the film itself: the compaction of the film reduces the water permeability and increases the salt removal rate; Membrane contamination: fouling, microorganisms, solid particles on the surface or inside the membrane.