Wastewater treatment project of textile printing industry

1、 Sources of textile printing and dyeing wastewater

1. Scouring wastewater 2. Desizing wastewater 3. Bleaching wastewater 4. Dyeing wastewater 5. Finishing wastewater 6. Printing wastewater

2、 Treatment methods of cotton textile printing and dyeing wastewater

Generally, the treatment methods of sewage are: physical method, chemical method, biological method, etc. (1) The so-called physical method is to use physical action to separate the main suspended pollutants in sewage without changing their chemical properties. The physical method is mainly used in the primary treatment of sewage, which is simple and economical. The main treatment technologies of physical method include regulation, filtration, sedimentation, centrifugal separation, floatation, etc. (2) The so-called chemical method is the use of chemical reaction to separate, recover pollutants in sewage, or make it into harmless substances. Chemical method is mainly effective in the treatment of inorganic or organic solutes in wastewater. (3) The so-called biological method is to use the metabolic function of microorganisms to degrade the dissolved and colloidal organic pollutants in water and transform them into harmless substances, so that the sewage can be evolved. Biological method is a widely used treatment method at present, which is often used in the secondary treatment of wastewater. There are aerobic and anaerobic treatment processes. Because of its high efficiency and wide application, aerobic biological treatment has become the mainstream of biological treatment. Aerobic biological treatment can be divided into activated sludge process and biofilm process.

The removal rates of CODCr, BOD5 and chroma are about 60%, 80% ～ 90% and 50% respectively. The removal rates of CODCr, BOD5 and chroma in the subsequent chemical treatment unit (coagulation sedimentation or air flotation) are 50% - 60%, 50% and 60% - 90%, respectively. Polyaluminum is often used as coagulant. The dosage should be determined by experiment. It is possible to discharge cod, BOD, chroma and other pollutants of dyeing wastewater by biochemical treatment. Considering all kinds of technical conditions, biological fluidized bed, contact oxidation and surface aeration should be preferred, and the treatment scheme can be selected according to the specific conditions of each plant. It is generally believed that when the amount of waste water is small (less than 500 m3 / D), contact oxidation coagulation sedimentation should be used; when the amount of waste water is large (more than 500 m3 / D), in order to save land occupation, it is recommended to use biological fluidized bed coagulation sedimentation. In addition to the above-mentioned typical processes, some special treatment technologies should be adopted for the water quality characteristics of specific discharge objects, such as alkalinity, chroma and the removal of some toxic substances.

3、 Reclaimed water reuse system after textile printing and dyeing wastewater treatment

Physicochemical + disinfection process can be used, as follows:;

Source water --- > regulating pool --- > filter --- > disinfection pool --- > storage pool --- > discharge when the residential sewage is used as the reclaimed water source, the biochemical + disinfection process can be adopted, as follows: source water --- > hydraulic screen --- > regulating pool --- > biochemical pool --- > filter --- > disinfection pool --- > storage pool --- > discharge. The above process facilities can be designed into ground or buried structure according to the specific situation of the site.