Reclaimed water recycling process and reclaimed water recycling system for wastewater in photovoltaic industry

Abstract

The invention discloses a reclaimed water reuse process and reclaimed water reuse system aiming at photovoltaic industry wastewater, and the reclaimed water reuse process comprises the following steps: firstly, pumping dilute acid water, dilute alkaline water and concentrated alkaline water into an adjusting tank according to a ratio, adding a reducing agent sodium hydrogen sulfite into the adjusting tank, controlling the ORP (oxidation reduction potential) of the mixed water to be-20-40mV, and controlling the pH value to be 9.0-11.0; mixed water in the adjusting tank is pumped into a reclaimed water recycling device to remove suspended solids, COD and salts, the reclaimed water recycling device comprises a sand filter tank, a carbon filter tank, a precision filter, an ultrafiltration membrane device and a reverse osmosis membrane device which are sequentially connected, produced water of the reverse osmosis membrane device enters a produced water barrel, concentrated water of the ultrafiltration membrane device and concentrated water of the reverse osmosis membrane device enter a concentrated water barrel, and the concentrated water of the ultrafiltration membrane device and the concentrated water of the reverse osmosis membrane device enter the reclaimed water recycling device. The concentrated water in the concentrated water barrel enters the concentrated water treatment unit to be subjected to pH adjustment and defluorination treatment, and finally the concentrated water reaches the standard and is discharged, a large amount of water resources in the photovoltaic industry can be recycled, the water resources are saved, and the system is stable in operation and low in operation cost.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly to a reclaimed water reuse process and system for photovoltaic industry wastewater. Background Art

[0002] The production of photovoltaic power generation systems involves the reprocessing of semiconductor silicon materials for power generation components, and a large amount of water, hydrofluoric acid, alkali and other raw materials are used, generating a large amount of wastewater. In the production stage of solar cell wafers, according to the existing process level, for every GW of production capacity, 500 - 1000 tons of wastewater are generated per day. The generated wastewater mainly contains fluorine and silicon, and has strong acidity or alkalinity, and can be divided into four categories: concentrated acid water, concentrated alkali water, dilute acid water, and dilute alkali water. The amount of this wastewater is very large. The traditional treatment method is to discharge it directly after mixing with other wastewater after meeting the fluorine removal standard, which will cause waste of water resources.

[0003] Currently, the reclaimed water reuse in photovoltaic enterprises generally focuses on the recovery of dilute acid water. After simple pretreatment such as pH adjustment of the dilute acid water, membrane equipment such as ultrafiltration and reverse osmosis is used for desalination, and then it is reused. The utility model patent with the patent number CN204417248U discloses a photovoltaic acid cleaning wastewater reuse device, which proposes to recover the acid cleaning wastewater by a reclaimed water reuse system composed of ultrafiltration, reverse osmosis and defluorination resin. However, in fact, the amount of dilute alkali water in photovoltaic industry wastewater is very large. If only dilute acid water is recovered, the overall water recovery rate will be low. Summary of the Invention

[0004] In order to overcome the above defects, the present invention provides a reclaimed water reuse process for photovoltaic industry wastewater. The reclaimed water reuse process and system for photovoltaic industry wastewater can recover and utilize a large amount of water resources in the photovoltaic industry, save water resources, and the system operates stably with low operating costs.

[0005] The technical solution adopted by the present invention to solve its technical problems: A reclaimed water reuse process for photovoltaic industry wastewater, comprising the following steps:

[0006] Step 1: Pump the dilute acid water, dilute alkali water and concentrated alkali water generated in the photovoltaic industry into the adjustment tank in proportion, and add the reducing agent sodium bisulfite into the adjustment tank to control the ORP of the mixed water at -20 - 40 mV, and control the pH of the mixed water within the range of 9.0 - 11.0;

[0007] Step 2: Pump the mixed water in the adjustment tank into the reclaimed water reuse device by a pump, and the reclaimed water reuse device removes the suspended solids, COD and salts in the mixed water;

[0008] Step 3: The water produced by the reclaimed water reuse device is transported to the production line for use by a pump.

[0009] Dilute acid water, dilute alkali water and concentrated alkali water are pumped into the adjustment tank according to a ratio. At the same time, the reducing agent sodium bisulfite is added to the mixed water. Sodium bisulfite undergoes a reduction reaction with hydrogen peroxide in the mixed water. Sodium bisulfite reacts with hydroxide ions in the mixed water to form sodium sulfite and water. Since sodium sulfite is still in a reduced state, sodium sulfite will continue to act as a reducing agent to undergo an oxidation-reduction reaction with hydrogen peroxide, decomposing hydrogen peroxide. In this way, on the one hand, the pH of the mixed water can be adjusted within the range of 9.0 - 11.0. This pH range meets the operating conditions of most membranes, and within this pH range, silicon exists in the form of silicate ions, preventing the formation of silicon scale and blocking the membrane material. At the same time, since the hydrogen peroxide in the wastewater is removed, the oxidation damage to the membrane structure of the reverse osmosis membrane is avoided, ensuring that the reclaimed water reuse device can treat the mixed water fully and effectively. The reclaimed water reuse device removes suspended solids, COD and particulate salts in the mixed water. The water produced by the reclaimed water reuse device can be pumped to the production line for reuse.

[0010] As a further improvement of the present invention, the dilute acid water, dilute alkali water and concentrated alkali water generated in the photovoltaic industry are respectively collected in a dilute acid water collection tank, a dilute alkali water collection tank and a concentrated alkali water collection tank. The homogenization device is used to homogenize the dilute acid water, dilute alkali water and concentrated alkali water in the dilute acid water collection tank, dilute alkali water collection tank and concentrated alkali water collection tank respectively. After homogenization, the dilute acid water, dilute alkali water and concentrated alkali water are pumped into the adjustment tank for mixing. The dilute acid water, dilute alkali water and concentrated alkali water are respectively homogenized in the dilute acid water collection tank, dilute alkali water collection tank and concentrated alkali water collection tank, so that the wastewater can maintain a stable pH after being pumped into the adjustment tank.

[0011] As a further improvement of the present invention, the dilute acid water in the dilute acid water collection tank is homogenized by mechanical stirring; the dilute alkali water in the dilute alkali water collection tank and the concentrated alkali water in the concentrated alkali water collection tank are both homogenized by aeration, and the residual hydrogen peroxide in the dilute alkali water and concentrated alkali water is reduced.

[0012] As a further improvement of the present invention, in step one, the dilute acid water, dilute alkali water and concentrated alkali water stay in the adjustment tank for 0.5 - 2 hours, which is used to ensure that the wastewater is fully mixed and reacts in the adjustment tank, facilitating subsequent treatment.

[0013] As a further improvement of the present invention, the reclaimed water reuse device in step three processes the mixed water in sequence through sand filtration, carbon filtration, precision filtration, ultrafiltration and reverse osmosis membrane treatment. The mixed water is controlled by the automatic control program of the control system to pass through the above links in sequence. Among them, sand filtration is used to intercept large particulate suspended solids in the mixed water, carbon filtration can adsorb COD in the mixed water, precision filtration and ultrafiltration are used to intercept residual fine particles in the mixed water, protect the reverse osmosis membrane from being polluted, and extend the service life of the reverse osmosis membrane. The reverse osmosis membrane is used for desalination to obtain reclaimed water with low conductivity.

[0014] As a further improvement of the present invention, the concentrated water of the ultrafiltration membrane device for ultrafiltration treatment of mixed water and the concentrated water of the reverse osmosis membrane device for reverse osmosis membrane treatment of mixed water both enter the concentrated water treatment unit. The concentrated water treatment unit adjusts the pH of the concentrated water and adds calcium salts for defluorination treatment, and the treated concentrated water meets the standards and is discharged.

[0015] A reclaimed water reuse system includes an adjustment tank, a reclaimed water reuse device, a concentrated water bucket, a product water bucket, a concentrated water treatment unit, several pumps and a control system. Among them, the reclaimed water reuse device includes a sand filter tank, a carbon filter tank, a precision filter, an ultrafiltration membrane device and a reverse osmosis membrane device. A dosing device is provided on the adjustment tank, and the dosing device can quantitatively add a reducing agent into the adjustment tank. The water outlet of the adjustment tank is communicated with the water inlet of the sand filter tank through a pipeline. The pump can pump the mixed water in the adjustment tank into the sand filter tank. The water outlet of the sand filter tank is connected to the water inlet of the carbon filter tank. The water outlet of the carbon filter tank is connected to the water inlet of the precision filter. The water outlet of the precision filter is pumped into the ultrafiltration membrane device through a pump for ultrafiltration treatment. The product water of the ultrafiltration membrane device is pumped into the reverse osmosis membrane device through a pump for reverse osmosis treatment. The product water outlet of the reverse osmosis membrane device is communicated with the product water bucket through a pipeline. The concentrated water outlets of the ultrafiltration membrane device and the reverse osmosis membrane device are communicated with the concentrated water bucket through a pipeline. The concentrated water bucket is communicated with the water inlet of the concentrated water treatment unit through a pipeline. The control system controls the operation of each pump and the dosing device of the adjustment tank.

[0016] The dilute acid water, dilute alkali water and concentrated alkali water are pumped into the adjustment tank for mixing in a certain proportion through a pump. A reducing agent sodium bisulfite is added into the adjustment tank through the dosing device to control the ORP at -20 - 40 mV and the pH within the range of 9.0 - 11.0. Then the mixed water is pumped into a reclaimed water reuse device formed by connecting a sand filter tank, a carbon filter tank, a precision filter, an ultrafiltration membrane device and a reverse osmosis membrane device in sequence through a pump. Among them, the sand filter tank is used to intercept large particle suspended solids in the incoming mixed water. The carbon filter tank can adsorb COD in the mixed water. The precision filter and the ultrafiltration membrane device are used to intercept the remaining fine particles in the water, protect the reverse osmosis membrane in the reverse osmosis membrane device from being polluted, and extend the service life of the reverse osmosis membrane. The reverse osmosis membrane device is used for desalination of the mixed water to finally obtain reclaimed water with low conductivity. The mixed water is controlled by the automatic control program of the control system to pass through the above links in sequence. Among them, the ultrafiltration concentrated water of the ultrafiltration membrane device and the reverse osmosis concentrated water of the reverse osmosis membrane device are collected in the concentrated water bucket, the product water of the reverse osmosis membrane device is collected in the product water bucket, the wastewater in the concentrated water bucket is transported by a pump to the next-level concentrated water treatment unit for further treatment, and the product water in the product water bucket is transported by a pump to the production line for use.

[0017] As a further improvement of the present invention, there are also provided a dilute acid water collection tank, a dilute alkali water collection tank, and a concentrated alkali water collection tank. The drain outlets of the dilute acid water collection tank, the dilute alkali water collection tank, and the concentrated alkali water collection tank are communicated with the inlet of the adjustment tank through pipelines. A stirrer is installed in the dilute acid water collection tank, and the stirrer can stir and homogenize the dilute acid water collected in the dilute acid water collection tank. A plurality of air diffuser pipes are installed at the bottom of the dilute alkali water collection tank and the concentrated alkali water collection tank. A plurality of air diffuser holes are opened on the side wall of the air diffuser pipe. The air diffuser pipe is communicated with a blower, and the blower can send compressed air into the air diffuser pipe. The air diffuser holes of the air diffuser pipe can aerate and homogenize the dilute alkali water collection tank and the concentrated alkali water collection tank. The dilute acid water, dilute alkali water, and concentrated alkali water in the photovoltaic industry are respectively collected in the dilute acid water collection tank, the dilute alkali water collection tank, and the concentrated alkali water collection tank, and the dilute acid water, dilute alkali water, and concentrated alkali water are homogenized, which can effectively reduce the residual hydrogen peroxide in the water.

[0018] As a further improvement of the present invention, the concentrated water treatment unit includes at least one stage of defluorination reaction tank. A dosing device is provided on the defluorination reaction tank, and the dosing device can add pH adjustment agents and calcium salts into each stage of the defluorination reaction tank. The effluent of the last stage of the defluorination reaction tank meets the discharge standard and is discharged. A pH meter is also provided in the defluorination reaction tank, and the pH meter can detect the pH of the wastewater in the defluorination reaction tank in real time. The control system controls the start and stop of the dosing device. The pH adjustment agent is an acidic agent. The dosing device first adds calcium salts, and the calcium ions in the calcium salts react with the fluoride ions in the concentrated water to form calcium fluoride precipitation. After the reaction, the pH is adjusted with acid, and finally the discharge requirements are met. The pH generally requires 6-9. The pH meter is used to control the pH of the effluent of the concentrated water treatment device to ensure that the effluent requirements are met.

[0019] The beneficial effects of the present invention are as follows: By jointly using the two types of wastewater with the largest volume in the photovoltaic industry (dilute acid water and dilute alkali water) and the difficult-to-treat concentrated alkali water for reusing intermediate water, the present invention can recover a large amount of water resources. The pH of the influent of the intermediate water reuse system is controlled within the range of 9.0-11.0, and this pH range meets the operating conditions of most membranes. And in this pH range, the silicon exists in the form of silicate ions and will not form silicon scale to cause blockage of the membrane material. By reducing hydrogen peroxide with a reducing agent, the oxidation damage of the reverse osmosis membrane caused by hydrogen peroxide in the wastewater is avoided, effectively prolonging the service life of the membrane material. The pH of the mixed wastewater formed by the dilute acid water and the dilute alkali water is adjusted by adding concentrated alkali water, and there is no need to add liquid alkali for adjustment, saving chemicals and reducing the cost of pH adjustment agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the system schematic diagram of the present invention.

[0021] Reference numerals: regulating tank---1; intermediate water reuse device---2; concentrated water bucket---3; product water bucket---4; concentrated water treatment unit---5; dilute acid water collection tank---6; dilute alkali water collection tank---7; concentrated alkali water collection tank---8; sand filter tank---21; carbon filter tank---22; precision filter---23; ultrafiltration membrane device---24; reverse osmosis membrane device---25. Detailed implementation manners

[0022] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described here are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the following embodiments, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0023] Embodiment: The wastewater quality indexes of a certain photovoltaic cell manufacturing factory are as follows:

[0024] Dilute acid water: water volume 100m 3 / d, fluoride ion concentration 245mg / L, silicon concentration 4.64mg / L;

[0025] Dilute alkali water; water volume 8m 3 / d, fluoride ion concentration 9.92mg / L, silicon concentration 120mg / L, hydrogen peroxide concentration <164.8mg / L;

[0026] Concentrated alkali water: water volume 10m 3 / d, fluoride ion concentration 14mg / L, silicon concentration 4041mg / L, hydrogen peroxide concentration <1482mg / L;

[0027] The intermediate water reuse process steps of the present invention for the above wastewater are as follows:

[0028] (1), Collect the dilute acid water, dilute alkali water and concentrated alkali water in the dilute acid water collection tank 6, dilute alkali water collection tank 7 and concentrated alkali water collection tank 8 respectively, wherein: the dilute alkali water collection tank 7 and the concentrated alkali water collection tank 8 are homogenized by aeration, and the dilute acid water collection tank 6 is homogenized by mechanical stirring;

[0029] (2), Pump the dilute acid water, dilute alkali water and concentrated alkali water in the dilute acid water collection tank 6, dilute alkali water collection tank 7 and concentrated alkali water collection tank 8 into the regulating tank 1 for mixing according to the ratio of dilute acid water: dilute alkali water: concentrated alkali water = 30:10:3, and add the reducing agent sodium bisulfite 0.25 - 0.4kg / m 3, the ORP of the mixed water in the regulating tank 1 is controlled within -10 - 30 mV, the pH is controlled within the range of 9.0 - 10.5, the residence time of the mixed water in the regulating tank 1 is 1 - 2 hours. At this time, the fluoride ion concentration of the mixed water in the regulating tank 1 is less than 80 mg / L, and the silicon concentration is 150 - 300 mg / L;

[0030] (3), Pump the mixed water in the regulating tank 1 into the reclaimed water reuse device 2. The reclaimed water reuse device 2 is composed of a sand filter tank 21, a carbon filter tank 22, a precision filter 23, an ultrafiltration membrane device 24, and a reverse osmosis membrane device 25 connected in sequence. The control system controls the mixed water to pass through the sand filter tank 21, the carbon filter tank 22, the precision filter 23, the ultrafiltration membrane device 24, and the reverse osmosis membrane device 25 in sequence through an automatic control program. Among them, the ultrafiltration concentrated water produced by the ultrafiltration membrane device 24 and the reverse osmosis concentrated water produced by the reverse osmosis membrane device 25 are collected in the concentrated water bucket 3, and the reverse osmosis water produced by the reverse osmosis membrane device 25 is collected in the product water bucket 4. The ultrafiltration recovery rate in this link is more than 95%, and the reverse osmosis recovery rate is more than 75%;

[0031] (4), The water produced in the product water bucket 4 is transported by a pump to the production line for use, and the concentrated water in the concentrated water bucket 3 is transported by a pump to the concentrated water treatment unit 5. Fluoride is removed by adjusting the pH and adding calcium salt agents, and the treated concentrated water meets the standards and is discharged.

[0032] After the system has been running for 6 months, the membrane flux of the reverse osmosis membrane device 25 has not shown obvious attenuation.

Claims

1. A water reuse process for photovoltaic industry wastewater, characterized by: The steps include: Step 1: The diluted acid water, diluted alkaline water and concentrated alkaline water generated by the photovoltaic industry are pumped into the regulating tank in proportion for mixing, and the reducing agent sodium bisulfite is added into the regulating tank to control the ORP of the mixed water within -20-40mV and the pH of the mixed water within the range of 9.0-11.0; Step 2: Pump the mixed water in the regulating tank into the reclaimed water reuse device, and remove the suspended solids, COD and salts in the mixed water by the reclaimed water reuse device; Step 3: The water produced by the reclaimed water reuse device is pumped to the production line for use.

2. The process for recycling wastewater from the photovoltaic industry according to claim 1 is characterized in that: The dilute acid water, dilute alkaline water and concentrated alkaline water generated by the photovoltaic industry are collected in the dilute acid water collection pool, the dilute alkaline water collection pool and the concentrated alkaline water collection pool respectively, and the dilute acid water, dilute alkaline water and concentrated alkaline water in the dilute acid water collection pool, the dilute alkaline water collection pool and the concentrated alkaline water collection pool are homogenized by a homogenizing device. The dilute acid water, dilute alkaline water and concentrated alkaline water after homogenization are pumped into the regulating tank for mixing.

3. The process for recycling wastewater from the photovoltaic industry according to claim 2 is characterized in that: The dilute acid water in the dilute acid water collection tank is homogenized by mechanical stirring; the dilute alkaline water in the dilute alkaline water collection tank and the concentrated alkaline water in the concentrated alkaline water collection tank are both homogenized by aeration, and the residual hydrogen peroxide in the dilute alkaline water and the concentrated alkaline water is reduced.

4. The process for recycling wastewater from the photovoltaic industry according to claim 1 is characterized in that: In step 1, the residence time of the dilute acid water, the dilute alkaline water and the concentrated alkaline water in the regulating tank is 0.5-2 hours.

5. The process for recycling wastewater from the photovoltaic industry according to claim 1 is characterized in that: The reclaimed water reuse device described in step three sequentially performs sand filtration, carbon filtration, precision filtration, ultrafiltration and reverse osmosis membrane treatment on the mixed water.

6. The process for recycling wastewater from the photovoltaic industry according to claim 5 is characterized in that: The concentrate from the ultrafiltration membrane device used for ultrafiltration treatment of mixed water and the concentrate from the reverse osmosis membrane device used for reverse osmosis membrane treatment of mixed water both enter the concentrate treatment unit, which adjusts the pH of the concentrate and adds calcium salt for defluorination treatment. The treated concentrate meets the standards and is discharged.

7. A reclaimed water reuse system used in the reclaimed water reuse process for photovoltaic industry wastewater according to any one of claims 1 to 6, characterized in that: It includes a regulating tank, a reclaimed water reuse device, a concentrated water tank, a water production tank, a concentrated water treatment unit, several pumps and a control system, wherein the reclaimed water reuse device includes a sand filter tank, a carbon filter tank, a precision filter, an ultrafiltration membrane device and a reverse osmosis membrane device, the regulating tank is provided with a dosing device, the dosing device can quantitatively add a reducing agent into the regulating tank, the water outlet of the regulating tank is connected to the water inlet of the sand filter tank through a pipeline, the pump can pump the mixed water in the regulating tank into the sand filter tank, the water outlet of the sand filter tank is connected to the water inlet of the carbon filter tank The water outlet of the carbon filter tank is connected to the water inlet of the precision filter, the water outlet of the precision filter is pumped into the ultrafiltration membrane device for ultrafiltration treatment, the water produced by the ultrafiltration membrane device is pumped into the reverse osmosis membrane device for reverse osmosis treatment, the water production port of the reverse osmosis membrane device is connected with the water production barrel through a pipeline, the concentrated water outlets of the ultrafiltration membrane device and the reverse osmosis membrane device are connected with the concentrated water barrel through a pipeline, the concentrated water barrel is connected with the water inlet of the concentrated water treatment unit through a pipeline, and the control system controls the operation of each pump and the dosing device of the regulating tank.

8. The reclaimed water reuse system according to claim 7, characterized in that: A dilute acid water collection pool, a dilute alkaline water collection pool and a concentrated alkaline water collection pool are also provided. The drainage outlets of the dilute acid water collection pool, the dilute alkaline water collection pool and the concentrated alkaline water collection pool are connected with the water inlet of the regulating pool through pipelines. A stirrer is installed in the dilute acid water collection pool, and the stirrer can stir and homogenize the dilute acid water collected in the dilute acid water collection pool. A plurality of aeration pipes are installed at the bottom of the dilute alkaline water collection pool and the concentrated alkaline water collection pool, and a plurality of aeration holes are opened on the side walls of the aeration pipes. The aeration pipes are connected with a blower, and the blower can send compressed air into the aeration pipes. The aeration holes of the aeration pipes can aerate and homogenize the dilute alkaline water collection pool and the concentrated alkaline water collection pool.

9. The reclaimed water reuse system according to claim 7, characterized in that: The concentrated water treatment unit comprises at least one stage of defluorination reaction tank, on which a dosing device is provided, which can add pH adjusting agent and calcium salt into each stage of defluorination reaction tank, and the effluent of the last stage of defluorination reaction tank meets the discharge standard for discharge, and a pH meter is also provided in the defluorination reaction tank, which can detect the pH of the wastewater in the defluorination reaction tank in real time, and a control system controls the start and stop of the dosing device.

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