CS237693B1 - Method of wastewater treatment containing inorganic pignents - Google Patents

Abstract

The solution concerns the purification of wastewater containing inorganic pigments, colloidal and suspended substances by clarification and coagulation with subsequent separation of the solid phase. The washing wastewater from the washing of thermal iron pigments is dosed as a coagulant. The dosage of this new coagulant, the required amount of which depends on the content of inorganic pigments in the purified wastewater, achieves satisfactory purification of wastewater. The required dose of the agent is determined by a coagulation experiment.

Description

The invention relates to the purification of wastewater containing inorganic pigments, colloidal and suspended substances by clarification and coagulation, with possible adjustment of the pH of the purified wastewater, with subsequent separation of the solid phase, using washing waters from washing thermal iron pigments.

Wastewater containing inorganic pigments, colloidal and suspended substances must be cleaned before being discharged into the stream. The classic technology for their cleaning consists of dosing a coagulant, possibly adjusting the pH, coagulation and sedimentation of the resulting suspension.

This method of purification involves the dosing of classical coagulants such as ferric chloride, aluminum sulfate or sodium aluminate. The production of these agents is too expensive and there is a shortage. They are used primarily for the treatment of drinking water and water for energy and industrial purposes.

Further clarification using green lye is known. This agent is cheap. However, difficulties can arise in the preparation and dissolution of green lye. They are caused by the so-called caking of green lye.

The use of ferric chlorosulfate, which is produced by oxidizing green feldspar with chlorine, is also known. The disadvantages are complications in chlorination of ferrous sulfate and a lack of chlorine.

For the treatment of saline or weakly acidic wastewater, the use of silica gel as an auxiliary coagulant is also known. The disadvantage is the transportation, storage and dosing of this agent,

Other known coagulant additives include bentonite, kaolin, ground limestone, etc. These substances are used as weighting agents in combination with classic coagulants.

- 2 coagulants, which are in short supply· ₂₃₇

It is also known to purify wastewater using organic high-molecular substances of various trade names. The disadvantage is their high price.

It has now been found that wastewater containing inorganic pigments, colloidal and suspended substances, such as wastewater from titanium white surface treatment, floor and ground washes including contaminated wastewater from deshlov, or mixtures of these and similar wastewaters, can be cleaned with high efficiency by dosing weakly acidic wastewater generated during the washing of thermal iron pigments. This new coagulant has mainly the following composition:

neutralization capacity up to pH 4.5 g/1 í^SO^ 2.4 - 7.0 neutralization capacity up to pH 9.0 g/1 3.9 - 9.0 soluble iron g/1 1.0 - 4.5 insoluble substances g/1 0.05 - 1.6 pH 1.8 - 2.5

The content of pigment iron oxide in the coagulant is not a problem in wastewater treatment. It is advantageous to dose the wash water from the first wash, which has a higher content of dissolved iron, into the treated wastewater as a coagulant.

The new coagulant, which is the wastewater from the washing of thermal iron pigments after sedimentation, is dosed into the treated wastewater without further treatment, including the remains of the pigment iron oxide. Then, after possible adjustment of the pH to a value of no more than 10.0, the treated wastewater is subjected to coagulation and separation of the solid phase, for example by sedimentation, in a manner usual in the clarification of wastewater with classic coagulants. It is also possible to use auxiliary coagulation agents of both inorganic and organic types, including high-molecular substances. The new coagulant is preferably dosed in the required amount directly into the sewerage system through which the treated wastewater flows into the treatment plant.

The amount of treated wastewater almost always fluctuates. The content of suspended solids, including pigments and colloidal substances, is not uniform either. The concentration of the active substance in wastewater from the washing of thermal iron pigments, used as a coagulant, is also not uniform. Therefore, it is useful to determine the most appropriate dose of the coagulant, for example

- 3 - 237 693 clarification experiment. On an operational scale, it is usually sufficient to set its dosage to a constant value, which corresponds to up to twice the amount of coagulant required for the average wastewater flow rate according to the clarification experiment. This ensures sufficient quality of the treated wastewater at increased wastewater flow rates through the treatment plant or at increased content of harmful substances in the wastewater. Higher dosage of the coagulant increases the efficiency of the treatment and is therefore not a defect. With this method of operation, up to 99.9% efficiency is achieved with appropriate dosage, based on suspended substances, including substances of pigment and colloidal nature, after sedimentation. With very high requirements for the quality of the treated wastewater, it is also possible to regulate the dosage of the coagulant according to clarification experiments and permanent analytical control of the iron content in the coagulant.

Example 1

To 50 m^/h of wastewater from the surface treatment of titanium white, which had a pH of 6.7 and contained 160 g/m^ of suspended substances, mainly Ti0 ₅ in the form of pigment, 5 m/h of wastewater from the washing of thermal iron pigments with the following composition was dosed directly into the weakly acidic sewage system before entering the treatment plant: neutralization capacity up to pH 4.5 g/1 H^SO^ 2.45 neutralization capacity up to pH 9.0 g/1 HgSO^ 3.92 total soluble iron g/1 1.12 insoluble substances g/1 0.09 pH 2.2

The dose of active substance in this case was 112 g/m3 of iron. The mixture of treated wastewater with this coagulant was alkalized to pH 9.5. After coagulation and sedimentation in a circular settler with a diameter of 15 m, the content of insoluble substances in the effluent was 15 g/m3.

Example 2

To a mixture of 85 m^/h of wastewater from the surface treatment of titanium white, washing water from the water treatment plant, acidified wastewater from the circulation cooling and polluted dešl wastewater from the terrain, which contained 6,300 g/m insoluble substances, 6 m^/h of water from the washing of thermal iron pigments with the following composition was added as a coagulant:

neutralizing capacity up to pH 4.5 g/1 H ₂ so ₄ 6.42 neutralizing capacity up to pH 9.0 g/1 h ₂ sat ₄ 8.88 total soluble iron g/1 3.50

237,693

Insoluble matter mixture g/1 0.06 pH Μ

The active substance load in this case was 247 g/m^ of iron.

wastewater and coagulant had the following composition: neutralizing capacity up to pH 4.5 g/1 H ₂ 30 ₄ 1.69 neutralizing capacity up to pH 9.0 g/1 _{H2SO4 2.95} total soluble iron g/1 0.26. total iron g/1 0.49 insoluble substances g/1 5.0 pH 3.2

After alkalization to pH 9.5, coagulation and sedimentation, the treated wastewater contained 26 g/m^ of insoluble substances.

Claims (1)

SUBJECT OF THE INVENTION Process for the purification of waste waters containing inorganic pigments, colloidal and suspended substances by clarification and coagulation, optionally adjusting the pH of the treated waste water and dosing inorganic or organic type coagulation aids, including high molecular weight substances, followed by solid phase separation, the coagulating agent feeds the wash water from the washing of thermal, cesium, pigments into the treated waste water.