Method and principle of sewage treatment

Sediment filtration method also has a problem worth noting, because the particulate matter is constantly blocked and accumulated, these substances may have bacteria multiply here, and release toxic substances through the filter, causing pyrogen reaction, so it is necessary to replace the filter frequently, in principle, when the pressure difference between the water and the water rises to five times the original, it is necessary to replace the filter.

Hard water softening

Softening of hard water requires the use of ion exchange method, its purpose is to use cation exchange resin to exchange sodium ions in hard water calcium and magnesium ions, in order to reduce the concentration of calcium and magnesium ions in the water source. The softening reaction is as follows:

Ca2++2Na-EX→Ca-EX2+2Na+1

Mg2++2Na-EX→Mg-EX2+2Na+1

EX represents ion exchange resins that bind Ca2+ and Mg2+ to release the Na+ ions originally contained in them.

resin matrix contains sodium chloride. In the process of hard water softening, sodium ions will gradually be used up, and the softening effect of exchange resin will gradually decrease. At this time, it is necessary to make regeneration work, that is, adding a specific concentration of saline at a fixed time, usually 10%. The reaction is as follows:

Ca-EX2+2Na+ (concentrated brine) → 2NA-EX +Ca2+

Mg-EX2+2Na+ (concentrated brine) → 2NA-EX +Mg2+

If there is no cation softening in the process of water treatment, not only the reverse osmosis membrane will have calcium and magnesium deposits, which will reduce the efficacy and even destroy the reverse osmosis membrane, and the patient is also easy to get hard water syndrome. The hard water softener can also cause bacterial reproduction problems, so the device needs to have the function of backflushing, and after a period of time it is necessary to backflush once to prevent too many impurities from adsorbed on it. Another noteworthy problem is hypernatremia, because the softening and rereduction process of dialysis water is controlled by a timer, the normal reduction occurs mostly in the middle of the night, which is controlled by the valve, if there is a failure, a large amount of salt water will flood into the water source, resulting in the patient's hypernatremia. The automatic sodium ion exchanger uses the principle of ion exchange to remove calcium, magnesium and other scale ions from water. When the raw water containing hardness ions passes through the resin layer in the exchanger, the calcium and magnesium ions in the water are replaced with the sodium ions adsorbed by the resin, and the calcium and magnesium ions are adsorbed by the resin and the sodium ions enter the water, so that the water flowing from the exchanger is the softened water with the hardness removed.

Activated carbon

Activated carbon is made of wood, wood scraps, fruit cores, coconut shells, coal or petroleum residue and other substances at high temperatures, and needs to be activated by hot air or water vapor after being made. Its main function is to remove chlorine and chloramines and other dissolved organic substances with molecular weights between 60 and 300 daltons. The surface of the activated carbon is granular, the interior is porous, and there are many capillaries of about 1Onm~lA size in the pores, and the internal surface area of the activated carbon of 1g is as high as 700-1400m2, and the internal surface of these capillaries and the particle surface are where the adsorption is. The factors that affect the ability of activated carbon to remove organic matter are the area of activated carbon itself, the size of the hole and the molecular weight and Polarity of the organic matter to be removed. It mainly has the physical adsorption capacity to remove debris. When the adsorption capacity reaches saturation, excessive impurities will fall down and pollute the downstream water quality. Therefore, it is necessary to periodically use the way of thrust to remove the impurities on the adsorption.

If the adsorption capacity of this activated carbon filter is significantly reduced, it must be updated. Measuring the difference in TOC concentration (or the difference in the number of bacteria) between inlet and outlet is one of the bases for considering the replacement of activated carbon. Some reverse osmosis membranes have poor tolerance to chlorine, so activated carbon should be treated before reverse osmosis, so that chlorine can be effectively adsorbed by activated carbon, but the bacteria adsorbed by the holes on activated carbon are easy to multiply and grow, and the efficacy of activated carbon is limited for the removal of organic matter with large molecules, so the reverse osmosis membrane must be reinforced in the back.

Deion process

The purpose of the deion method is to remove inorganic ions dissolved in water, and the same as the hard water softener, also uses the principle of ion exchange resin. Two resins are used here - cation exchange resins and anion exchange resins. Cation exchange resin uses hydrogen ions (H+) to exchange cations; The anion exchange resin uses hydroxide ions (OH-) to exchange anions, and hydrogen ions and hydroxide ions combine to form neutral water, the reaction equation is as follows: