SU1736939A1 - Method for purification of sewage from calcium and magnesium compounds - Google Patents

Abstract

The invention relates to methods for purifying water from hardness salts in ion-exchange plants and allows reducing the consumption of reagents and preventing contamination of the environment with inorganic salts. The method is carried out by treating wastewater with Na-cationation, regeneration of the cation exchanger with sodium chloride solution, treatment of the spent regeneration solution (OPP), its return to regeneration, while regeneration of the cation exchanger is carried out with a 15–18% NaCI solution 7-10 m / h with removal of wash water before and after regeneration in quantities corresponding to 0.5 filter volume, mixing it with regeneration products in the form of ORR, which is heated to 65-70 ° C before return, treated with soda ash in an amount equivalent to the concentration of calcium ions, and with a flow rate of 0.01-0.05 m / h, is fed to a thin layer settler for clarification and settling, and after removal of calcium carbonate is treated with sodium hydroxide in an amount equivalent to the concentration of magnesium ions, and sent to filtration to separate magnesium hydroxide. When separating the sediments, the thin layer settler and the filter are washed with purified water with an intensity of 20-25 l / s m for 2-3 minutes. 2 hp f-ly, 1 tab. 10 s

Description

The invention relates to methods for purifying water and wastewater from inorganic substances, in particular water and wastewater from water treatment plants, and can be used in industries that use calcium and magnesium compounds.

There is a known method of water softening on a sodium-cation filter, when it is regenerated with sodium chloride, treating the spent regeneration solution (ORR) with lime and soda, settling and bleaching and returning the purified solution to regeneration.

However, this process of water and wastewater treatment from calcium compounds

and magnesium is spent without utilization of the components is unreasonable, since the introduction of lime first, and then soda, leads to the loss of lime on the reaction product of magnesium with magnesium chloride at pH 10-10.5 and subsequent precipitation of calcium ions when interacting with the resulting calcium chloride and excess lime.

The aim of the invention is to save reagents and prevent contamination of the environment with inorganic salts.

The goal is achieved by the fact that, according to the method of water treatment and purification of water, the detachment of calcium and magnesium, including

Na-cationation, the regeneration of the cation exchanger with sodium chloride solution, the reagent treatment of the spent regeneration solution, its clarification and settling, the return of the purified solution to regeneration, the regeneration of the cation exchanger lead to a 15–18% solution of sodium chloride with its transmission rate 7 -10 m / h with removal of filtrate from the volume of cation exchanger before regeneration - 0.5 free volume of cation exchanger, regeneration products - 1 free volume of cation exchanger, after regeneration of wash water - 0.5 free volume of cation exchanger in ETS waste, regenerant, wherein the spent regeneration solution before returning to the regeneration is heated to 65-70 ° C. is treated with soda ash and at a flow rate of 0.01-0.05 m / h is fed into a thin lagoon for clarification and settling, and after removing calcium carbonate, the solution is treated with sodium hydroxide and sent for filtration with magnesium hydroxide separation.

The dose of soda ash is equivalent to the concentration of calcium ions, and sodium hydroxide is equivalent to the concentration of magnesium ions.

The separation of calcium carbonate and magnesium hydroxide is carried out separately by washing the filter and the sump with purified water with an intensity of 20-25 l / s m for 2-3 minutes.

All products of regeneration are utilized, there is no waste, it saves natural resources, eliminates environmental pollution.

Example. The artesian water was softened with an initial hardness of 18.5 mg-eq / l of Na-cationification using KU-2-8 cation exchanger. Regeneration of the cation exchanger was performed with a 15% solution of table salt. The hardness of the products of regeneration is 255 mg-eq / l, of which Ca is 145 mg-eq / l. The residual NaCl was 5.6–8.1%.

The solution was heated to 70 ° C and dispensed with a flow rate of 0.03 m3 / h per thin sedimentation tank as described in a well-known installation with a capacity of 1 m3 / h, including a thin sedimentation tank and filter. The loading of a filter of a known installation is glass balls ФЗ mm, a grid cell above the filter 2x2 mm.

The dose of NaaCOs is 145 mEq / L: the dose of NaOH is 110 mEq / L.

The data from wastewater treatment from a mixture of calcium and magnesium solutions are tabulated.

As can be seen from the table, according to the proposed method, complete separation and utilization of regeneration products occurs with a concentration after regeneration up to 20% instead of mixing them, discharging into natural reservoirs and dumping or reuse at a concentration of only 2% after regeneration. Economical natural resources are utilized inorganic substances from wastewater, water pollution is excluded.

Using a solution of NaCI less than 15% reduces the residual concentration of it in the products of regeneration and increases the amount of evaporated water, which leads to an increase in energy consumption. Using a solution of more than 18% leads to inconvenience in operation, its volume is less than the free volume in the filter (including loading) and

the regeneration continuity process is disrupted.

The removal of water of 0.5 volume before regeneration and after regeneration together with the products of regeneration is optimal with

point of view, the residual concentration of NaCI, taking into account the cost of heat for its further evaporation, is sufficient as a buffer in order to avoid the overshoot of regeneration salts at the beginning of regeneration into the filtrate and at the end

wash it in recycled water.

At 65-70 ° C, CaCO3 and Md (OH) 2 are deposited 1.5 times faster than at temperatures up to 65 ° C. Heating above 80 ° С

increases energy costs.

Dosing of 0.01-0.05 m3 / h of regeneration products per 1 m / h of plant capacity is optimal in terms of settling time and lightening effect 92-95% of suspended matter

CaCO3 and Md (OH) 2.

Input (MaASOZ at the entrance of a known installation contributes 92-95% of CaCO3 in a thin settling tank; input of NaOH at the inlet to the filter of the installation contributes 92-95% release of MD (OH) 2 in the layer of filter loading of the installation.

Serving an equivalent amount of Na2COs to an equivalent amount of CaClz and

NaOH - MgCl2 contributes to the economically optimal regeneration of the spent solution,

The MD (OH) 2 is disposed of by flushing the filter loading of an installation with an intensity of 22-25 l / s m2 with a separate removal of the washing products vertically upwards. The washing intensity of less than 22 l / s m2 degrades its quality by 25%, as the sediment remains in the loading layer, with more than 25

l / s filter loading is pressed against the screen above the filter.

Utilization of CaCO3 is carried out by washing the filter with the same intensity after separating Md (OH) 2 with the removal of products of washing down the installation,

Washing time of 2-3 minutes is optimal for the flow of wash water and energy consumption.

The use of the proposed method of water treatment and wastewater treatment for calcium and magnesium compounds provides the following advantages as compared with the known methods: wastelessness, production safety, economy of natural resources, disposal of purification products, while eliminating environmental pollution.

Claims (3)

1. A method of purifying wastewater from calcium and magnesium compounds, including water softening by Na-cationization, regeneration of the cation exchanger with sodium chloride solution, washing, reagent treatment of the spent regeneration solution, its clarification and settling, return of the purified solution to regeneration, characterized by that, in order to save reagents for processing and to prevent pollution of the environment with inorganic salts, regeneration of the cation exchanger is carried out with a 15-18% solution of sodium chloride at a flow rate of 7-10 m / h with removal of wash water before and after regeneration in quantities corresponding to 0.5 filter volumes, and mixing it with the products of regeneration in the form of spent regeneration solution, which is heated to 65-70 ° C before returning to regeneration, treated with soda ash and at a flow rate of 0.01-0.05 m / h is fed to the thin layer settler for clarification and settling, and after separated and calcium carbonate is treated with sodium hydroxide and filtered for separation of magnesium hydroxide. 2. A method according to claim 1, characterized in that the dose of soda ash is taken to be equivalent to the concentration of calcium ions, and sodium hydroxide is equivalent to the concentration of magnesium ions. 3. A method according to claims 1 and 2, characterized in that the separation of calcium carbonate and magnesium hydroxide is carried out separately when washing the sump and filter with purified water of 20-25 l / s m2 in volume for 2-3 minutes.