Low-carbon near zero emission process of industrial waste water

Abstract

A low-carbon near zero emission process of industrial waste water, comprising: S1: entering industrial waste water into a pre-oxidation system to improve biodegradability of organics; S2: after treatment in the pre-oxidation unit, entering the waste water into an anaerobic biological treatment system, sodium chloride and sulfate is deeply removed and carbon sources in the waste water can be used to remove the sulfate and nitrate; S3: entering water output from the anaerobic biological treatment system into a membrane concentration system and membrane concentrated solution enters a nano-filtration salt fractionation system for salt fractionation; and S4: refluxing nano-filtration concentrate solution generated by the nano-filtration salt fractionation system to the anaerobic biologic treatment system for biological desulfurization, or synthesizing the nano-filtration concentrate solution to be sodium persulfate by electro chemical methods, and refluxing proportionately to a waste water pre-oxidation system for use in-situ.

Claims

1. An emission process of industrial waste water, comprising: S1: feeding industrial waste water into a oxidation system through a regulating tank, and then oxidizing toxic functional groups, to improve biodegradability of organics those are difficult to degrade in the waste water, wherein the functional groups comprise aromatic functional groups, heterocyclic, cyano-, nitro- and halogenated groups; S2: after treatment in the oxidation unit, entering the waste water into an anaerobic biological treatment system, wherein anaerobic de-nitrification and sulfate reduction occurs and sodium chloride and sulfate are removed such that the sodium chloride and sulfate do not enter an evaporation and crystallization system, and hydrogen sulfide generated during anaerobic biological processes is used to produce sulfur or combined in a desulfurization tower for treatment; S3: entering water effluent from the anaerobic biological treatment system into a membrane concentration system comprising ultrafiltration and reverse osmosis, wherein water discharged by the membrane concentration system is recycled for industrial use and membrane retentate enters a nano-filtration desalination system for salt fractionation; and S4: refluxing nano-filtration concentrate solution generated by the nano-filtration salt fractionation system to the anaerobic biologic treatment system for biological desulfurization, or reacting the nano-filtration concentrate solution to be sodium persulfate by electro chemical methods, and refluxing proportionately to the waste water oxidation system for use in-situ and feeding water generated during nano-filtration into the evaporation and crystallization system to produce sodium chloride; wherein, oxidation of the waste water in step S1 is done in a continuous stirred and oxidation degree of the waste water is controlled by types, amounts and HRT of the oxidants; and the oxidation degree of the waste water is judged by biological usability of organics in the water based on BOD.sub.5 (biological oxygen demand over 5 days)/COD (chemical oxygen demand) of the oxidized waste water and salinity; wherein, the oxidants comprise any one or combination of ozone, hydrogen peroxide and sodium persulfate; a BOD5/COD content in the oxidized waste water after oxidation is 0.380.47; and an HRT during oxidation is 0.32 h; wherein, the anaerobic biologic treatment system in step S2 comprises an anaerobic reactor selected from upflow anaerobic sludge blanket (UASB), anaerobic baffled reactor (ABR), continuous agitated-tank reactor (CSTR) and an anaerobic biofilter anaerobic reactor; microorganisms use carbon-source in the waste water as an electron donor, anaerobic de-nitrification and sulfate reduction occurs, sodium chloride and sulfate is removed; and partitions are provided in the anaerobic reactor or a cascade reactor for partitioned enrichment of denitrifying bacteria and sulfate-reducing bacteria; wherein, a pH value in the anaerobic reactor is 5.57.8; HRT is 10120 h, DO<0.3 mg/L, ORP300 mv, temperature 2835 C., a COD volume load is 0.310 kgCOD/(m.sup.3.Math.d), a total nitrogen volume load is 0.023.5 kgN/(m.sup.3.Math.d) and a sulfate load is 0.031.2 kgSO42-/(m.sup.3.Math.d); wherein, the nano-filtration concentrate solution in the step S4 comprises sodium sulfate water, for the nano-filtration concentrate solution with a sodium sulfate concentration less than 5 g/L, refluxing to the anaerobic biological treatment system for biological desulfurization; for nano-filtration concentrate solution with the sodium sulfate concentration more than 5 g/L, synthesizing sodium persulfate by electrochemical methods, and refluxing to the oxidation system of the waste water for use in-situ; wherein, electrochemical synthesis of the sodium persulfate is done is a diaphragm cell, the diaphragm cell comprises an anode tank, a diaphragm, a cathode tank and a stirrer; entering the nano-filtration concentrate water into an anode unit of the diaphragm cell for preparing the sodium persulfate; a material for preparing an anode of the diaphragm cell comprises a Pt electrode or a boron-doped diamond electrode; a material for preparing a cathode of the diaphragm cell comprises a stainless steel electrode or a graphite electrode; and the diaphragm comprises a cation-exchange membrane; wherein, a current strength and electrolyzing time during electrolyzing and synthesizing the sodium chloride is determined by a concentration of the sulfur in the nano-filtration concentrate water such that, when the nano-filtration concentrate solution has a sulfur concentration of 510%, a current density is 30500 mA/cm.sup.2, and the electrolyzing time is 60120 min; and when the nano-filtration concentrate solution has a sulfur concentration of 1040%, the current density is 30500 mA/cm.sup.2 and the electrolyzing time is 120300 min.

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5. (canceled)

6. The emission process of industrial waste water according to claim 1, wherein, the membrane concentration system in the step S3 comprises an ultrafiltration system and a reverse osmosis system, the ultrafiltration system in the membrane concentration system is connected with the anaerobic biological treatment system to remove substances, particles and colloid matters in the anaerobic biological system; the ultrafiltration system is connected with the reverse osmosis system, the ultrafiltration system further removes soluble matter via the reverse osmosis system to produce regenerated water, and reverse osmosis concentrate water is configured to remove monovalent salts and bivalent salts via a nano-filtration salt fractionation system.

7. (canceled)

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Description

BRIEF DESCRIPTION OF DRAWINGS

[0054] FIG. 1 shows a flow diagram of a novel low-carbon near zero emission of industrial waste water according to the present invention.

EMBODIMENTS

[0055] Hereinafter a further description will be given to the present invention in conjunction with the embodiments.

Embodiment 1

Low-carbon Near Zero Emission of Coking Waste Water in an Industrial Park

[0056] The phenol and cyanogen waste water in a coke oven plant in an industrial park with the process according to the present invention, the COD of the waste water was 3120 mg/L, the sulfate content was 514.9 mg/L, the nitrate content was 138.6 mg/L, the pH value 8.48, the temperature 65 C., and the B/C value 0.22.

[0057] First of all, introducing the coking waste water into the pre-oxidation treatment unit, using the persulfate synthesized using conventional electrochemical systems as oxidants, adding 3 g/L, with the thermo energy in the coking waste water, by thermo activating the persulfate and generating sulfate radicals and hydroxyl radicals, reacting the radicals with the organics those were difficult to degrade, by hydrogen abstraction actions, electron transfer or addition, loops and bonds in the organics those were difficult to degrade were broken, and the organics were decomposed to be small molecule matters, after mechanically stirring for 60 min (500 rpm), pre-oxidation was done, the COD, sulfate, nitrate and B/C of the water after pre-oxidation treatment reached respectively 3670 mg/L, 597.6 mg/L, 126.6 mg/L and 0.4 and the biodegradability of the water was obviously improved.

[0058] Pumping the water output by the pre-oxidation pool to a UASB reactor, adjusting conditions of anaerobic reaction to ensure that the soluble oxygen concentration is no more than 0.5 mg/L, the oxidation-reduction potential is no more than 300 mv, and maintaining the reaction temperature to be 301 C., in the meanwhile, controlling the hydraulic retention time to be 30 hours, further, draining the sludge periodically and maintaining the age of the anaerobic sludge is 25 days, maintaining the concentration of the sludge in the reactor to be 15-18 g/L, giving mechanical stirring reaction at a speed of 500 rpm, the biotreated effluent COD, sulfate and nitrate were respectively 330.7 mg/L, 38.1 mg/L and 27.9 mg/L, highly efficient extraction of the organics, nitrate and sulfate, reached respectively 89.4%, 92.6% and 79.9%.

[0059] After treating the anaerobically treated water with the membrane concentration unit, the effluent was recycled, the membrane concentration solution entered the nano-filtration salt fractionation unit, and nano-filtration water containing primarily sodium chloride and nano-filtration concentrate water containing primarily sulfate was obtained, wherein the nano-filtration water was transported to the evaporation and crystallization unit to obtain high quality sodium chloride, and the nano-filtration concentrate water entered the conventional electrochemical synthesizing unit to synthesize sodium persulfate and was refluxed to the pre-oxidation unit for waste water pretreatment.

Embodiment 2

[0060] Low-carbon Near Zero Emission of Kaliferous Waste Water of a Printing and Dyeing Company

[0061] The present invention was used for treating the kaliferous waste water from a printing and dyeing company, wherein the COD of the waste water was 23270 mg/L, the sulfate content was 1264.8 mg/L, the nitrate content was 764.2 mg/L, the pH value was 12, the temperature was 35 C. and the B/C value was 0.18.

[0062] First of all, introducing the kaliferous waste water into the pre-oxidation treatment unit, using the ozone as the oxidant with an amount of 21.7 mg/L, in 60 min, the pre-oxidation was done, the B/C value of the pre-oxidized output water reached 0.39 and the biodegradability of the output water was apparently improved.

[0063] Pumping the pre-oxidized output water into a UASB reactor, adjusting conditions of anaerobic reaction to ensure that the soluble oxygen concentration was no more than 0.5 mg/L, the oxidation-reduction potential was no more than 300 mv, maintaining the reaction temperature at 301 C., controlling the hydraulic retention time to be 60 hours, further, draining the sludge periodically and maintaining the age of the sludge to be 23 days, maintaining the sludge concentration in the reactor to be 2530 g/L, allowing mechanical stirring reaction at a speed of 500 rpm, removing the pollutants taking use of the differences in abilities of the microorganisms in gaining and losing electrons at different valence states of elements, the COD, sulfate and nitrate of the biotreated effluent were respectively 4607.5 mg/L, 125.5 mg/L and 209.4 mg/L, the effective removal rate of organics, nitrate and sulfate were achieved, which were respectively 80.2%, 91.4% and 72.6%.

[0064] For the anaerobic treated water, after being treated by the membrane concentration unit, the effluent was recycled, the membrane concentration solution entered the nano-filtration salt fractionation unit, and obtained the nano-filtration effluent containing primarily sodium chloride and the nano-filtration concentrate water containing primarily sulfate, wherein, the nano-filtration water was transported to the evaporation and crystallization unit to obtain high quality sodium chloride; while the nano-filtration concentrate water was refluxed to the anaerobic biological treatment unit for biological desulfurization treatment.

[0065] The foregoing is a detailed description on the embodiments of the present invention, however, the present invention is not limited to the foregoing embodiment, in the range of the knowledge that those skilled in the art have, a variety of changes can be made without departing from the essence of the present invention.