Printing and dyeing industry wastewater depth treatment and reuse technology

Printing and dyeing industry wastewater depth treatment and reuse technology 1 domestic printing and dyeing wastewater treatment and reuse status quo China has more research on printing and dyeing wastewater reuse, from the current research and application of the situation mainly has the following characteristics: (1) reuse technology is mostly in the experimental research stage Mostly for small and pilot tests, the actual engineering application is less, and the water return rate is low, generally not more than 50%, mainly for the water quality requirements are not high for the front process, the lack of conducive to improve the water quality and return rate of the promotion and application of efficient technology.
(2) reuse treatment is mainly on the basis of printing and dyeing wastewater in the standard treatment to further treatment, to meet the water quality standards.
process mainly uses coagulation, adsorption, filtration and oxidation, among which the key techniques for removing salinity and hardness are studied less.
(3) Due to the limitations of existing technology levels, the large reuse of printing and dyeing wastewater poses a number of problems for production and wastewater treatment systems, including the accumulation of organic pollutants and inorganic salts.
of water quality problems and the impact on water treatment systems for long-term reuse of wastewater are not well studied, especially the accumulation of inorrided salts.
2 Printing and dyeing wastewater deep treatment reuse technology and process printing and dyeing wastewater depth treatment mainly for conventional secondary treatment system water treatment, the removal of pollutants are mainly color, COD and salinity (conductivity), so that the water quality to meet the requirements of the production process.
printing and dyeing process and product quality requirements are different, the water quality requirements for return water are also different.
, China does not yet have a unified standard for the water quality of printing and dyeing wastewater.
industry experience, water quality indicators must be controlled within water indicators.
, the textile printing and dyeing industry on the return water quality requirements are much higher than the urban water quality requirements.
2.1 Depth Treatment Unit Technology 2.1.1 Adsorption treatment technology passes wastewater through a filter bed consisting of adsorbents, and the contaminated substance is adsorbed on or filtered away.
activated carbon is a commonly used adsorbent in the deep treatment of printing and dyeing wastewater, its micro-porous, than the surface area can be as high as 500 to 600 m2/g, with a strong adsorption decoloring performance, especially suitable for the relative molecular mass of less than 400 water-soluble dye decolor adsorption.
but activated carbon adsorption effect on hydrophobic dyes is poor, its regeneration is more complex and expensive, limiting the application of adsorption method in the deep treatment of printing and dyeing wastewater.
natural minerals such as kaolin, diatom soil, active white soil and coal powder also have high adsorption properties, and are also used in the deep treatment of printing and dyeing wastewater.
2.1.2 membrane separation technology film has a pass-through difference between different substances, membrane separation technology is the use of this characteristic of the membrane, in a certain mass transmission driving force, the mixture separation method.
separation techniques used for deep treatment of printing and dyeing wastewater are microfiltration (MF), ultrafiltration (UF), filtration (NF) and reverse osmosis (RO).
MF and UF are often pre-treated as NF and RO; UF can separate large molecule organic matter, collosomes, suspended solids; NF can desalinate and concentrate at the same time; RO can remove soluble metal salts, organic matter, gels, etc. and intercept all ions. The advantages of
membrane separation technology are: It can not only remove residual organic matter in water, reduce color, but also remove inorganic salts, prevent the accumulation of inorganic salts in the system, is a promising technology in the deep treatment of printing and dyeing wastewater.
, however, the membrane treatment process is more expensive and the membrane components are susceptible to contamination and shorten their service life.
only by controlling and reducing membrane pollution to extend membrane life, thereby reducing costs, membrane separation technology in the printing and dyeing wastewater depth treatment will be more widely used.
2.1.3 Advanced Oxidation Depth Treatment Technology (1) Chemical Oxidation Technology.
O3 and Fenton reagents are commonly used oxidants in the deep treatment of printing and dyeing wastewater.
O3 has a strong decolorization effect, although the removal effect of COD is very small, but can change the B/C of wastewater, thereby improving the bioaturation of wastewater.
the main advantages of O3 oxidation are simple and compact equipment, small footprint, easy to achieve automatic control, the main disadvantage is that the treatment cost is high, not suitable for the treatment of high-flow wastewater.
Fenton reagents are oxidants made from a combination of H2O2 and Fe2 plus, produced under acidic conditions. OH has a very strong oxidation effect, especially suitable for the treatment of dye wastewater with more complex components.
Fenton oxidation has a strong removal capacity for COD and chroma, the presence of iron ions may affect the color of water and the pH of the reaction is low, which may affect other processing processes.
(2) photo catalytic oxidation technology.
use strong oxidants to produce strong oxidation capacity under UV radiation. OH treatment wastewater, with low energy consumption, no secondary pollution, complete oxidation and other advantages, commonly used UV /Fenton, UV/O3, UV/H2O2 and so on.
photocatalytic research is also based on photosensitive semiconductors as catalysts, where TiO2 photocatalysts are widely used and have good processing effects.
TiO2 in the light radiation, its price belt will produce an electron hole (h-plus) pair, TiO2 surface adsorption of organic matter is strong oxidation of h-plus active, oxidation and degradation.
the adsorption properties of activated carbon can help solve the problem of tiO2 loss, separation and recovery, and improve the treatment effect of photocatalyst.
the light transmission and light utilization of wastewater itself restrict the application of photo catalytic technology in wastewater treatment industry.
(3) electrochemical oxidation technology.
Under the action of an auspicuous electric field, a large number of freelance fundamentals are produced within a specific reactor through certain chemical reactions, electrochemical processes or physical processes, and the process of degradation of pollutants in wastewater is carried out by using the strong oxidation of free fundamentals.
electrochemical technology has the characteristics of easy control, no pollution or less pollution, high flexibility and so on.
2.1.4 High-efficiency biological treatment technology printing and dyeing wastewater secondary water pollutants are not biochemical, biodegradation is difficult, biological law focuses on the development of new bioreactive devices to enhance biotechnology, in order to further remove COD and chroma.
(1) Aeration Biofiltration Tank (BAF).
printing and dyeing wastewater after secondary biochemical treatment, COD and BOD in the water is relatively low, aeration biological filter tank fillers on the growth of poor nutritional microorganisms such as prosthetic monocytobacteria, spores, etc. , larger than the surface area, the organic matter in the wastewater has a strong affinity.
biological concentration and organic load in the aeration biofiltration tank, the treatment effect is stable and the water quality is good.
filter filter in the filter tank, the smaller the treatment effect is better, but the small particle size will make the working cycle shorter, the filter material is not easy to clean, the corresponding backflush water will also increase.
therefore the selection of suitable filter particle size is the key to give full play to the function of aeration biofiltration tank.
(2) mobile bed biofilm reactor (MBBR).
MBBR is a new type of biofilm reactor.
microorganisms are rich in fillers in the reactor, fillers are suspended in the reactor and flow with the mixture, so gas, water, fillers can be fully exposed in the reactor, oxygen utilization rate and organic pollutants transmission efficiency is high, and the activity of biofilms is high, aging biofilms easily fall off the filler surface.
MBBR also has the advantages of not requiring backflushing, strong impact load and stable water quality.
there are many varieties of organic pollutants in printing and dyeing wastewater, and the multi-bacterial system on biofills has greater degradation capacity, so MBBR as a deep treatment process has a great advantage to the secondary biochemical treatment of water with lower organic matter concentration.
the future, MBBR in the printing and dyeing wastewater depth treatment research and application as a development direction.
(3) membrane bioreacter (MBR).
bioreactive device combines membrane separation with biodegradation to remove most of the residual COD, chroma and all SSs in wastewater.
and then through the NF (RO) process to further treatment, remove most of the salinity, water quality can generally meet the requirements of return water.
mbR has the advantages of short process, small footprint and stable water quality, and similar disadvantages to membrane separation technology, mainly due to short membrane life, high cost and high power consumption caused by membrane pollution.
2.2 Printing and dyeing wastewater deep treatment reuse integrated process 2.2.1 Traditional technology combination process due to the complexity of printing and dyeing wastewater water quality, wastewater reuse is difficult to achieve by a single technology, so it is necessary to combine various methods organically, using a combination of processes for integrated treatment.
single technology for deep treatment, it is difficult to solve the problems of decolorization, COD reduction and desalination at the same time, a variety of single technology organic combination, can get better treatment results, but also to ensure that the advantages of each technology, improve the rate of pollutant removal.
2.2.2 membrane technology and traditional technology integrated process printing and dyeing wastewater composition is complex, such as membrane selection technology to treat printing and dyeing wastewater, we must choose a suitable pretreated process to prevent collocy, organic matter, suspended matter and other pollution of the membrane. The pollution problem of
membrane restricts the application of membrane technology in printing and dyeing wastewater treatment, and the use of O3 oxidation and other pretreatment means to control membrane pollution, thereby increasing the service life of the membrane and reducing the cost of treatment, is a major trend of deep treatment of printing and dyeing wastewater in the future.
2.2.3 Integrated membrane treatment reuse process many foreign studies have proved that the combination of different membrane separation technology, the composition of integrated membrane process, is an important direction of printing and dyeing wastewater depth treatment.
NF or RO as a deep treatment solution is feasible, RO water can be used back for any printing and dyeing process, NF is not as good as RO in terms of desalination and removal of minerals, but the operating cost is lower than RO.
these studies show the future direction of wastewater depth treatment technology, that is, to make full use of a variety of process technology integration, improve the degree of wastewater treatment, to achieve wastewater recycling is the ultimate goal of z.
3 Conclusion and outlook printing and dyeing wastewater has posed a serious threat to China's water environment, with the enhancement of people's awareness of environmental protection, printing and dyeing wastewater deep treatment and reuse more and more attention by the government.
For printing and dyeing wastewater deep treatment of a single technology more and each has advantages and disadvantages, but it is difficult to meet the discharge and reuse standards, according to the characteristics of printing and dyeing wastewater water quality, reasonable selection and optimization of the combination of treatment processes.
film separation technology is an important research direction for the deep treatment of printing and dyeing wastewater.
Future research can be based on unit technology improvement, including bio-chemical, materialized treatment effect improvement, difficult-to-degrade organic matter treatment technology improvement and membrane component pollution control, and then form a set of water to meet the water quality standards, high reuse rate and efficient and economical printing and dyeing wastewater reuse integration technology.