CN112079479B - Fertilizer-driven forward osmosis mariculture wastewater treatment system and treatment method - Google Patents
Fertilizer-driven forward osmosis mariculture wastewater treatment system and treatment method Download PDFInfo
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F9/00—Multistage treatment of water, waste water or sewage
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- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/445—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by forward osmosis
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
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- C02F2101/00—Nature of the contaminant
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/08—Seawater, e.g. for desalination
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/20—Nature of the water, waste water, sewage or sludge to be treated from animal husbandry
Abstract
A fertilizer-driven forward osmosis mariculture wastewater treatment system and a treatment method belong to the technical field of aquaculture. The fertilizer-driven forward osmosis mariculture wastewater treatment system is provided with the forward osmosis concentration unit, the forward osmosis ammonium recovery unit and the magnesium ammonium phosphate precipitation separation unit, so that the diluted drawing liquid is used as a magnesium nitrate and ammonium compound fertilizer solution which can be directly used in farmlands, and the cost of the drawing liquid regeneration process is eliminated. PO in cultivation wastewater 4 3‑ And residual NH 4 + Mg which is reversely penetrated through the permeable membrane in the magnesium nitrate drawing liquid 2+ The magnesium ammonium phosphate (struvite) solid fertilizer is produced by chemical reaction crystallization precipitation. The nitrogen and phosphorus nutrients in the cultivation wastewater are recycled, so that the cultivation wastewater is purified, and the purified cultivation wastewater can be recycled. Concentrated seawater is used as the drawing liquid in the forward osmosis concentration process, so that the cost of the drawing liquid regeneration is greatly reduced.
Description
Technical Field
The invention relates to a fertilizer-driven forward osmosis mariculture wastewater treatment system and a treatment method, and belongs to the technical field of aquaculture.
Background
The circulating mariculture is a highly intensive culture mode using artificial feed, and at present, open running water or semi-running water culture is mainly adopted. About 90% and 82% of nitrogen and phosphorus contained in the bait put in the culture are accumulated in the culture water body in the form of residual bait and fish excreta, a large amount of feed is wasted, the culture cost is high, the discharged culture wastewater causes seawater eutrophication in the coastal water area, and red tide occurs in the local sea area; the circulating seawater culture is easy to be restricted by external marine environment, once the external seawater quality is deteriorated or polluted, the yield and quality of the aquatic products are seriously threatened, and the culture benefit is reduced. Therefore, the research on the purification treatment and the recycling of the circulating mariculture wastewater is a key technology for realizing ecological fishery culture.
Compared with domestic wastewater and industrial wastewater, the cultivation wastewater has the characteristics of low pollutant concentration and large wastewater discharge amount, and the treatment difficulty is increased. The existing wastewater treatment methods mainly comprise a physical treatment method, a chemical treatment method and a biological treatment method. Filtration and foam separation techniques commonly used in physical treatment methods can remove suspended matters in wastewater, and are difficult to remove pollutants such as inorganic matters, total nitrogen, total phosphorus and the like. The chemical method mainly adopts flocculating agent, chemical oxidant and the like to treat the wastewater to remove harmful substances such as ammonia, nitrite, organic matters and the like in the wastewater, but the chemical reagent dosage is large, the energy consumption is high, and the wastewater treatment cost is too high. Biological treatment utilizes absorption and metabolism of microorganisms, plants and the like to degrade nutrient components in wastewater, but artificial wetland with good treatment effect, microalgae treatment technology and the like have the problems of large occupied land area and large investment.
In order to solve the problems of high cost and poor treatment effect of the culture water, a membrane separation technology is selected for treating the culture wastewater. Pressure-driven nanofiltration and reverse osmosis treatment technology is characterized by that the membrane is used for treating NH in waste water 4 + The retention rate of organic matters is low, the waste water separation effect is poor, and more importantly, the water quantity of the culture waste water is large and nanofiltration is carried out +The reverse osmosis membrane method has high electricity consumption and high cultivation wastewater treatment cost. Forward osmosis relies on the osmotic pressure of the solution to push the separation process, does not need to consume pumping work to overcome the osmotic pressure, has the advantages of low energy consumption, high retention rate, low membrane pollution tendency and the like, and becomes an emerging wastewater treatment technology. Based on forward osmosis technology, the waste water is treated by using fertilizer as a drawing liquid, the treated drawing liquid can be directly used as crop fertilizer, the fertilizer drives the forward osmosis technology to be mainly used for urine treatment and sea water desalination, and the concentration of nitrogen and phosphorus in urine is 5-8 times of that of sea water culture waste water, so that the treatment efficiency of recovering nitrogen and phosphorus and other nutrient substances by adopting forward osmosis treatment of sea water culture waste water is too low, and NH in the culture waste water is reduced 4 + The retention rate is low, and nitrogen in the wastewater cannot be effectively recovered. The fertilizer-driven forward osmosis seawater desalination is mainly used for separating fresh water in seawater, and the concentrated seawater is discharged to the sea, so that the recycling of nitrogen and phosphorus nutrients in the aquaculture wastewater cannot be realized, and the treatment and recycling of the aquaculture wastewater cannot be realized. Therefore, development of a fertilizer-driven forward osmosis mariculture wastewater treatment process which is suitable for the characteristics of the culture wastewater and has low cost and good treatment effect is needed.
Chinese patent publication numbers CN102351367A and CN108975568A disclose a method for treating mariculture wastewater, which adopts an electrochemical technology and an ultraviolet irradiation disinfection technology to partially remove ammonia nitrogen and kill germs in the wastewater, but has unsatisfactory removal effect on total phosphorus, organic matters and the like, the treated wastewater meets the standard for discharge, nutrient substances in the culture wastewater are not effectively recovered, the water quantity of the mariculture wastewater is large, the power consumption of the wastewater treatment is high, and the treatment cost of the mariculture wastewater is not effectively reduced.
The Chinese patent publication numbers CN105502650A and CN106890625A disclose a treatment method for removing nitrogen and phosphorus in aquaculture wastewater, but the chemical reagent added in wastewater treatment is large in quantity and unrecoverable, so that the operation cost is high, the sludge production is large, secondary pollution is caused, phosphorus in the wastewater is not recycled, the treated aquaculture wastewater is not effectively purified, and the quality of aquaculture water is seriously affected by long-term recycling.
The screening of chemical fertilizer driving liquid in forward osmosis water and fertilizer integrated irrigation in 37 volumes 9 in industrial water treatment 2017 researches the performance of 4 chemical fertilizer solutions as the extracting liquid in the treatment of heavy metal cadmium solution by a forward osmosis method, and the aim of comparison research is to screen the extracting liquid with the optimal performance, but the method does not relate to the treatment of concentrated raw material liquid and the recycling of nutrient substances in the raw material liquid.
The method for treating the seawater culture wastewater has the following problems:
(1) The existing physical method, chemical method and biological method wastewater treatment technologies realize wastewater purification through filtration separation, chemical oxidative decomposition and biological absorption metabolism, and pollutants in the cultivation wastewater are difficult to thoroughly remove by the methods, so that the wastewater treatment cost is too high due to excessive medicament and power consumption of wastewater treatment.
(2) The technical problems of high treatment cost, easy scaling of the membrane and the like exist in the membrane method treatment of the culture wastewater such as pressure-driven nanofiltration, reverse osmosis and the like due to the large discharge amount of the culture wastewater and high power consumption of the pressure-driven membrane method.
(3) When the fertilizer-driven forward osmosis wastewater treatment technology is adopted to recover nutrients such as ammonia nitrogen in the aquaculture wastewater, the concentration of the nutrients in the raw material liquid is too low, the forward osmosis nutrient recovery efficiency is too low, and NH in the aquaculture wastewater 4 + The retention rate is low, and nitrogen in the wastewater cannot be effectively recovered. When the technology is adopted for seawater desalination, pollutants in seawater are not treated, concentrated seawater is directly discharged to the sea, and the purification treatment of the aquaculture seawater and the recycling of nutrient substances such as nitrogen, phosphorus and the like in the aquaculture seawater cannot be realized.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a fertilizer-driven forward osmosis mariculture wastewater treatment system and a treatment method. The treatment system provides concentrated seawater and Mg (NO) 3 ) 2 The solution is used as the forward osmosis method coupling of the drawing liquid, thereby realizing the recycling of nitrogen and phosphorus nutrient substances in the mariculture wastewater as crop fertilizers, realizing the recycling of the culture seawater and realizing the low-cost zero discharge of the mariculture wastewater.
The invention adopts the following technical scheme: the utility model provides a fertilizer drive forward osmosis mariculture wastewater treatment system, it includes pretreatment unit, and it still includes forward osmosis concentration unit, forward osmosis ammonium recovery unit and magnesium ammonium phosphate precipitation separation unit, pretreatment unit contains wastewater disposal basin, flocculation charge device and filtering ponds, and the delivery port of wastewater disposal basin passes through the water inlet of first water pump and wastewater piping connection filtering ponds, and the inside of filtering ponds is equipped with grid device, and flocculation charge device's play medicine mouth passes through piping connection wastewater piping.
The forward osmosis concentration unit comprises a drawing liquid forward osmosis membrane device and a drawing liquid slurry preparation tank, a water outlet of the filtering tank is connected with a feed inlet at the left upper part of the drawing liquid forward osmosis membrane device through a second water pump, a drawing liquid outlet at the top of the drawing liquid slurry preparation tank is connected with a drawing liquid inlet at the right upper part of the drawing liquid forward osmosis membrane device through a first drawing liquid pump, a drawing liquid outlet at the right lower part of the drawing liquid forward osmosis membrane device is connected with a drawing liquid inlet at the bottom of the drawing liquid slurry preparation tank through a slurry preparation branch pipe and a water inlet of the seawater tank through a water inlet branch pipe, and a water outlet of the seawater tank is connected with the mariculture tank through a seawater conveying pipeline.
The forward osmosis ammonium recovery unit comprises a magnesium nitrate drawing liquid pool, a fertilizer drawing liquid forward osmosis membrane device and a fertilizer pool, wherein a discharge hole of the magnesium nitrate drawing liquid pool is connected with a drawing liquid inlet at the left upper part of the fertilizer drawing liquid forward osmosis membrane device through a second drawing liquid pump, a drawing liquid outlet at the left lower part of the fertilizer drawing liquid forward osmosis membrane device is connected with a feed inlet of the fertilizer pool, and a discharge hole at the left lower part of the drawing liquid forward osmosis membrane device is connected with a feed inlet at the right upper part of the fertilizer drawing liquid forward osmosis membrane device.
The magnesium ammonium phosphate precipitation separation unit comprises a stirring reactor, a filter, a centrifugal separator and a magnesium ammonium phosphate fertilizer tank, wherein a discharge port at the right lower part of the fertilizer drawing liquid forward osmosis membrane device is connected with a feed port of the stirring reactor through a third water pump and a reactor feed pipe, a discharge port at the bottom of the stirring reactor is connected with the feed port at the bottom of the filter through a fourth water pump, a solid discharge port at the right side of the filter is connected with the feed port of the centrifugal separator, a discharge port of the centrifugal separator is connected with the feed port of the magnesium ammonium phosphate fertilizer tank, a liquid discharge port at the top of the filter is connected with a feed branch pipe through a branch pipe, and the other branch pipe is connected with the reactor feed pipe.
The liquid-drawing forward osmosis membrane device and the fertilizer liquid-drawing forward osmosis membrane device are divided into a raw material liquid chamber and a liquid-drawing chamber through forward osmosis membranes.
The treatment method of the fertilizer driven forward osmosis mariculture wastewater treatment system comprises the following steps of:
a) Pretreatment of the cultivation wastewater, wherein the cultivation wastewater in the wastewater tank is pumped into a filter tank through a wastewater pipeline by a first water pump, a flocculating agent in a flocculating and dosing device is added into the cultivation wastewater through the wastewater pipeline, the cultivation wastewater completes flocculating precipitation in the filter tank, suspended particles are removed through a grid device, and the pretreated cultivation wastewater enters a forward osmosis concentration unit for continuous treatment.
b) The method comprises the steps of forward osmosis concentration of the aquaculture wastewater, pumping pretreated aquaculture wastewater into a raw material liquid side of a liquid-extract forward osmosis membrane device through a second water pump, pumping concentrated seawater with concentration of 20-25% in a liquid-extract slurry preparation tank into a liquid-extract side of a liquid-extract forward osmosis membrane component through a first liquid-extract pump, concentrating salinity of the aquaculture wastewater to 10-12% under the action of forward osmosis pressure, diluting concentration of the liquid-extract to 12-15%, feeding part of diluted liquid-extract into the liquid-extract slurry preparation tank, adding sea salt into the liquid-extract slurry preparation tank for recycling, feeding the rest part of concentrated aquaculture wastewater into a sea water tank, and continuously treating by a forward osmosis ammonium recovery unit.
c) Recovering forward osmosis ammonium of the culture wastewater, enabling the concentrated culture wastewater to enter a raw material liquid side of a fertilizer drawing liquid forward osmosis membrane device, pumping a magnesium nitrate solution with the concentration of 14-16% in a magnesium nitrate drawing liquid pool as drawing liquid into a drawing liquid side of a fertilizer drawing liquid forward osmosis membrane component by a second drawing liquid pump, and under the action of osmotic pressure on two sides of a forward osmosis membrane, pumping NH in the culture wastewater 4 + And water molecules penetrate through the permeable membrane and enter the drawing liquid, the drawing liquid containing magnesium nitrate and ammonium ions enters the fertilizer pool for farmland fertilizer, and a small amount of Mg in the magnesium nitrate drawing liquid 2+ Penetrating through the permeable membrane and entering into the culture wastewater, and concentrating for the second time to obtain a concentrated solution containing Mg 2+ 、PO 4 3- And NH 4 + The culture seawater enters a magnesium ammonium phosphate precipitation separation unit to carry out crystallization precipitation treatment.
d) Precipitation separation of magnesium ammonium phosphate in the culture wastewater, and feeding the culture seawater after secondary concentration into a stirring reactor, wherein Mg in the culture seawater 2+ 、PO 4 3- And NH 4 + And (3) performing chemical reaction in the stirring reactor to generate magnesium ammonium phosphate precipitate, filtering the magnesium ammonium phosphate precipitate by a filter, enabling the magnesium ammonium phosphate precipitate to enter a centrifugal separator from a solid discharge port for solid-liquid separation to obtain a crystalline magnesium ammonium phosphate solid fertilizer, returning part of the culture seawater after filtering and separating by the filter to the stirring reactor for continuous precipitation reaction, returning the other part of the culture seawater to a seawater tank, mixing the culture seawater with fresh seawater, and enabling the culture seawater to enter a mariculture pond for repeated recycling.
The technical scheme is characterized in that: the forward osmosis process of magnesium nitrate fertilizer as the drawing liquid recovers NH in the seawater culture wastewater 4 + And PO (PO) 4 3- The magnesium nitrate and ammonium compound fertilizer solution and magnesium ammonium phosphate (struvite) solid fertilizer are obtained, the energy consumption in the process of regenerating the drawing liquid is eliminated, the seawater culture wastewater after forward osmosis treatment is purified, and the seawater culture wastewater can directly enter a seawater culture pond for recycling. The concentration of ammonia nitrogen nutrition in the seawater culture wastewater is increased in the forward osmosis concentration process of the concentrated seawater as the extracting solution, the recovery efficiency of the ammonia nitrogen nutrition in the forward osmosis ammonium recovery unit is improved, and the cost of the extracting solution regeneration is greatly reduced by taking the concentrated seawater as the extracting solution.
The beneficial effects of the invention are as follows: the fertilizer-driven forward osmosis mariculture wastewater treatment system comprises a pretreatment unit, a forward osmosis concentration unit, a forward osmosis ammonium recovery unit and a magnesium ammonium phosphate precipitation separation unit, wherein the treatment system is characterized in that the forward osmosis concentration unit, the forward osmosis ammonium recovery unit and the magnesium ammonium phosphate precipitation separation unit are arranged, so that after the culture wastewater is subjected to forward osmosis treatment by taking magnesium nitrate solution as a drawing liquid, part of NH in the wastewater is recovered from the magnesium nitrate drawing liquid 4 + And clean water, the diluted drawing liquid is used as magnesium nitrate and ammonium compound fertilizer solution which can be directly used for farmland, thereby eliminating the drawingCost of the liquid regeneration process. PO in cultivation wastewater 4 3- And residual NH 4 + Mg which is reversely penetrated through the permeable membrane in the magnesium nitrate drawing liquid 2+ The magnesium ammonium phosphate (struvite) solid fertilizer is produced by chemical reaction crystallization precipitation. The nitrogen and phosphorus nutrients in the cultivation wastewater are recycled, so that the cultivation wastewater is purified, and the purified cultivation wastewater can be recycled. The concentrated seawater is used as the extracting solution in the forward osmosis concentration process, and the coastal local material sea salt is used for regenerating the concentrated seawater extracting solution, so that the cost of extracting solution regeneration is greatly reduced. And (3) regenerating a part of diluted concentrated seawater by using the concentrated seawater drawing liquid, and circularly and repeatedly using the rest part of diluted concentrated seawater in a mariculture pond.
Drawings
FIG. 1 is a schematic diagram of a fertilizer driven forward osmosis mariculture wastewater treatment system.
In the figure: 1. the device comprises a wastewater tank, 1a, a first water pump, 1b, a wastewater pipeline, 2, a flocculation dosing device, 3, a filter tank, 3a, a grid device, 3b, a second water pump, 4, a drawing liquid forward osmosis membrane device, 5, a drawing liquid slurry preparation tank, 5a, a first drawing liquid pump, 5b, a slurry preparation branch pipe, 6, a magnesium nitrate drawing liquid pond, 6a, a second drawing liquid pump, 7, a fertilizer drawing liquid forward osmosis membrane device, 7a, a third water pump, 8, a fertilizer pond, 9, a stirring reactor, 9a, a fourth water pump, 9b, a reactor feed pipe, 10, a filter, 11, a centrifugal separator, 12, a magnesium ammonium phosphate fertilizer tank, 13, a seawater tank, 13a and a water inlet branch pipe.
Detailed Description
The technical scheme of the present invention will be clearly and completely described below with reference to the embodiments of the present invention and the accompanying drawings. In the description of the invention, the connection between the devices is a pipe connection, and the concentration is mass percent unless specified.
FIG. 1 shows a schematic diagram of a fertilizer driven forward osmosis mariculture wastewater treatment system. In the figure, this kind of fertilizer drive forward osmosis mariculture wastewater treatment system includes pretreatment unit, forward osmosis concentration unit, forward osmosis ammonium recovery unit and magnesium ammonium phosphate precipitation separation unit, and pretreatment unit contains waste water pond 1, flocculation charge device 2 and filtering ponds 3, and the delivery port of waste water pond 1 passes through the water inlet of filtering ponds 3 is connected to first water pump 1a and waste water pipe 1b, and the inside of filtering ponds 3 is equipped with grid device 3a, and the play medicine mouth of flocculation charge device 2 passes through pipe connection waste water pipe 1b.
The forward osmosis concentration unit comprises a drawing liquid forward osmosis membrane device 4 and a drawing liquid slurry preparation tank 5, a water outlet of the filtering pond 3 is connected with a feed inlet at the left upper part of the drawing liquid forward osmosis membrane device 4 through a second water pump 3b, a drawing liquid outlet at the top of the drawing liquid slurry preparation tank 5 is connected with a drawing liquid inlet at the right upper part of the drawing liquid forward osmosis membrane device 4 through a first drawing liquid pump 5a, a drawing liquid outlet at the right lower part of the drawing liquid forward osmosis membrane device 4 is connected with a drawing liquid inlet at the bottom of the drawing liquid slurry preparation tank 5 through a slurry preparation branch pipe 5b and is connected with a water inlet of a seawater tank 13 through a water inlet branch pipe 13a, and a water outlet of the seawater tank 13 is connected with a seawater culture pond through a seawater conveying pipeline.
The forward osmosis ammonium recovery unit comprises a magnesium nitrate drawing liquid pool 6, a fertilizer drawing liquid forward osmosis membrane device 7 and a fertilizer pool 8, wherein a discharge hole of the magnesium nitrate drawing liquid pool 6 is connected with a drawing liquid inlet at the left upper part of the fertilizer drawing liquid forward osmosis membrane device 7 through a second drawing liquid pump 6a, a drawing liquid outlet at the left lower part of the fertilizer drawing liquid forward osmosis membrane device 7 is connected with a feed inlet of the fertilizer pool 8, and a discharge hole at the left lower part of the drawing liquid forward osmosis membrane device 4 is connected with a feed inlet at the right upper part of the fertilizer drawing liquid forward osmosis membrane device 7.
The magnesium ammonium phosphate precipitation separation unit comprises a stirring reactor 9, a filter 10, a centrifugal separator 11 and a magnesium ammonium phosphate fertilizer tank 12, wherein a discharge port at the right lower part of the fertilizer drawing liquid forward osmosis membrane device 7 is connected with a feed port of the stirring reactor 9 through a third water pump 7a and a reactor feed pipe 9b, a discharge port at the bottom of the stirring reactor 9 is connected with a feed port at the bottom of the filter 10 through a fourth water pump 9a, a solid discharge port at the right side of the filter 10 is connected with the feed port of the centrifugal separator 11, a discharge port of the centrifugal separator 11 is connected with the feed port of the magnesium ammonium phosphate fertilizer tank 12, and a liquid discharge port at the top of the filter 10 is connected with a feed pipe 13a through one branch pipe and is connected with the reactor feed pipe 9b through another branch pipe.
The liquid-drawing forward osmosis membrane device is divided into a raw material liquid chamber and a liquid-drawing chamber by a forward osmosis membrane.
The treatment method of the fertilizer driven forward osmosis mariculture wastewater treatment system comprises the following steps:
a) In the pretreatment unit, seawater culture wastewater in a wastewater tank 1 for seawater culture is pumped into a filter tank 3 through a wastewater pipeline 1b by a first water pump 1a, and flocculation chemicals in a flocculation dosing device 2 are added into the culture wastewater through the wastewater pipeline 1b. After the aquaculture wastewater flows through the grid device 3a, flocculation precipitation is completed in the filter tank 3, suspended particles in the aquaculture wastewater are removed, the concentration of solid suspended matters in the pretreated aquaculture wastewater reaches below 100mg/L, and the pretreated aquaculture wastewater is used as feed liquid of a forward osmosis concentration unit for continuous treatment;
b) In the forward osmosis concentration unit, the salinity after pretreatment is between 3 and 3.2 percent, PO 4 3- The concentration is 120-150mg/L, NH 4 + The cultivation wastewater with the concentration of 60-80 mg/L is pumped into the raw material liquid chamber of the drawing liquid forward osmosis membrane device 4 of the concentrated seawater through the first water pump 1a, the concentrated seawater with the concentration of 20-25% in the drawing liquid slurry preparation tank 5 is taken as the drawing liquid, the first drawing liquid pump 5a pumps into the drawing liquid chamber of the drawing liquid forward osmosis membrane device 4 of the concentrated seawater, under the action of forward osmosis pressure, water in the cultivation wastewater penetrates through the osmosis membrane to enter the drawing liquid chamber, the salinity of the cultivation wastewater is concentrated to 10-12%, and PO 4 3- Concentrating to 400-600mg/L, NH 4 + Concentrating to 200-300mg/L, diluting the salinity of the concentrated seawater extract to 12-15%, adding a part of diluted concentrated seawater into an extract slurry preparation tank 5 of the concentrated seawater, adding sea salt into the concentrated seawater extract slurry for preparing and recycling, adding the rest part of the concentrated seawater extract slurry into a seawater tank 13, and continuously treating the concentrated aquaculture wastewater as a feed liquid of a forward osmosis ammonium recovery unit;
c) In the forward osmosis ammonium recovery unit, concentrated culture wastewater enters a raw material liquid chamber of a fertilizer drawing liquid forward osmosis membrane device 7, a magnesium nitrate solution with the concentration of 14-16% in a magnesium nitrate drawing liquid pond 6 is pumped into a drawing liquid chamber of the fertilizer drawing liquid forward osmosis membrane device 7 by a second drawing liquid pump 6a, and then is purified in a forward osmosis modeNH in concentrated cultivation wastewater under the action of osmotic pressure on two sides of osmotic membrane 4 + And water molecules penetrate through the permeable membrane and enter the drawing liquid chamber, and 40-60% of NH in the cultivation wastewater is recovered 4 + The fertilizer is diluted to 7-9% by magnesium nitrate drawing liquid, the obtained compound fertilizer solution of magnesium nitrate and ammonium enters a fertilizer pool 8 for farmland fertilizer, and a small amount of Mg in the magnesium nitrate drawing liquid 2+ Mg in the culture seawater at the discharge port of the fertilizer drawing liquid forward osmosis membrane device 7 enters the raw material liquid chamber through the osmosis membrane 2+ The concentration is 200-300mg/L, PO 4 3- The concentration is 600-850mg/L, NH 4 + The concentration is 150-220Mg/L, and Mg is contained after secondary concentration 2+ 、PO 4 3- And NH 4 + The concentrated culture seawater is used as feed liquid of a magnesium ammonium phosphate precipitation separation unit for crystallization and precipitation treatment;
d) In the magnesium ammonium phosphate precipitation separation unit, the culture seawater after secondary concentration enters a stirring reactor 9, and Mg in the culture seawater 2+ 、PO 4 3- And NH 4 + The chemical reaction takes place in the stirring reactor 9 to generate magnesium ammonium phosphate sediment, magnesium ammonium phosphate flows out from a solid discharge port after passing through a filter 10 and enters a centrifugal separator 11 to realize solid-liquid separation, the crystalline magnesium ammonium phosphate solid fertilizer is obtained, part of the culture seawater separated by the filter 10 returns to the stirring reactor 9 to continuously complete the chemical reaction, and the other part is taken as PO removal 4 3- And NH 4 + The seawater is returned to the seawater tank 13, mixed with uncontaminated fresh seawater introduced from the open sea, and then enters the mariculture pond for repeated recycling.
By adopting the technical scheme, the culture wastewater after flocculation clarification pretreatment enters a concentrated seawater drawing liquid forward osmosis concentration unit for pre-concentration, and the salinity is between 3 and 3.2 percent and PO is carried out under the action of osmotic pressure 4 3- The concentration is 120-150mg/L, NH 4 + Clear water in the mariculture wastewater with the concentration of 60-80 mg/L is permeated through the permeable membrane to enter concentrated seawater drawing liquid with the salinity of 20-25%, and a part of diluted concentrated seawater is added with sea salt to prepare the recycled concentrated seawater drawing liquidThe rest is used for recycling the mariculture pond together with the introduced fresh seawater. The sea salt is taken on site for regenerating the concentrated seawater drawing liquid, so that the cost of the drawing liquid regeneration in the forward osmosis process is reduced, and the clear water recovered from the seawater culture wastewater is recycled in the seawater culture pond; PO in concentrated mariculture wastewater 4 3- And NH 4 + The concentration is increased, and the recovery efficiency of ammonia nitrogen nutrients in the follow-up forward osmosis ammonium recovery unit is improved.
The magnesium nitrate fertilizer solution with the concentration of 14-16% is used as the drawing liquid of the forward osmosis ammonium recovery unit, and 40-60% of NH in the mariculture wastewater is recovered by the drawing liquid 4 + And clear water, the drawing liquid with the concentration of 7-9% after dilution is a compound fertilizer solution of magnesium nitrate and ammonium, and the drawing liquid can be directly used as fertilizer for farmlands, so that the cost of the drawing liquid regeneration process is eliminated; small amount of Mg in magnesium nitrate fertilizer drawing liquid 2+ Reverse osmosis membrane is adopted to enter the mariculture wastewater, and chemical reaction is adopted to react with PO in the mariculture wastewater 4 3- And NH 4 + The reaction generates magnesium ammonium phosphate (struvite) solid fertilizer, the nitrogen and phosphorus nutrient substances in the cultivation wastewater are recovered, the cultivation wastewater is purified, and the purified concentrated seawater and part of the concentrated seawater at the outlet of the liquid side of the drawing liquid of the forward osmosis concentration unit are collected together with fresh seawater and then enter a mariculture pond for repeated use.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting. Although the invention has been described in detail with reference to the foregoing embodiments, those skilled in the art may still make modifications to the technical solutions described in the foregoing embodiments, or may make equivalent substitutions for some or all of the technical features thereof; such modifications and substitutions do not depart from the spirit of the invention.
Claims (3)
1. The utility model provides a fertilizer drive forward osmosis mariculture wastewater treatment system, it includes pretreatment unit, its characterized in that: the flocculation chemical adding device comprises a wastewater tank (1), a flocculation chemical adding device (2) and a filtering tank (3), wherein a water outlet of the wastewater tank (1) is connected with a water inlet of the filtering tank (3) through a first water pump (1 a) and a wastewater pipeline (1 b), a grid device (3 a) is arranged in the filtering tank (3), and a chemical outlet of the flocculation chemical adding device (2) is connected with the wastewater pipeline (1 b) through a pipeline;
the forward osmosis concentration unit comprises a drawing liquid forward osmosis membrane device (4) and a drawing liquid slurry preparation tank (5), wherein the drawing liquid in the drawing liquid slurry preparation tank (5) is concentrated seawater with concentration of 20-25%, a water outlet of a filter tank (3) is connected with a feed inlet at the left upper part of the drawing liquid forward osmosis membrane device (4) through a second water pump (3 b), a drawing liquid outlet at the top of the drawing liquid slurry preparation tank (5) is connected with a drawing liquid inlet at the right upper part of the drawing liquid forward osmosis membrane device (4) through a first drawing liquid pump (5 a), a drawing liquid outlet at the right lower part of the drawing liquid forward osmosis membrane device (4) is connected with a drawing liquid inlet at the bottom of the drawing liquid slurry preparation tank (5) through a slurry preparation branch pipe (5 b) and a water inlet of a seawater tank (13), and a water outlet of the seawater tank (13) is connected with a seawater culture tank through a seawater conveying pipeline;
the forward osmosis ammonium recovery unit comprises a magnesium nitrate drawing liquid pool (6), a fertilizer drawing liquid forward osmosis membrane device (7) and a fertilizer pool (8), wherein the magnesium nitrate drawing liquid pool (6) contains magnesium nitrate solution with the concentration of 14-16%, a discharge port of the magnesium nitrate drawing liquid pool (6) is connected with a drawing liquid inlet at the left upper part of the fertilizer drawing liquid forward osmosis membrane device (7) through a second drawing liquid pump (6 a), a drawing liquid outlet at the left lower part of the fertilizer drawing liquid forward osmosis membrane device (7) is connected with a feed inlet of the fertilizer pool (8), and a discharge port at the left lower part of the drawing liquid forward osmosis membrane device (4) is connected with a feed inlet at the right upper part of the fertilizer drawing liquid forward osmosis membrane device (7);
the magnesium ammonium phosphate precipitation separation unit comprises a stirring reactor (9), a filter (10), a centrifugal separator (11) and a magnesium ammonium phosphate fertilizer tank (12), wherein a discharge hole at the right lower part of a fertilizer drawing liquid forward osmosis membrane device (7) is connected with a feed hole of the stirring reactor (9) through a third water pump (7 a) and a reactor feed pipe (9 b), a discharge hole at the bottom of the stirring reactor (9) is connected with a feed hole at the bottom of the filter (10) through a fourth water pump (9 a), a solid discharge hole at the right side of the filter (10) is connected with the feed hole of the centrifugal separator (11), a discharge hole at the top of the centrifugal separator (11) is connected with the feed hole of the magnesium ammonium phosphate fertilizer tank (12), and a liquid discharge hole at the top of the filter (10) is connected with a water inlet branch pipe (13 a) through another branch pipe and is connected with the stirring reactor feed pipe (9 b).
2. A fertilizer driven forward osmosis mariculture wastewater treatment system according to claim 1, characterized in that the draw liquid forward osmosis membrane device (4) and the fertilizer draw liquid forward osmosis membrane device (7) are separated into a raw material liquid chamber and a draw liquid chamber by a forward osmosis membrane.
3. A method of treating a fertilizer driven forward osmosis mariculture wastewater treatment system of claim 1, comprising the steps of:
a) Pretreatment of the cultivation wastewater, wherein the cultivation wastewater in a wastewater tank (1) is pumped into a filter tank (3) through a wastewater pipeline (1 b) by a first water pump (1 a), a flocculating agent in a flocculating and dosing device (2) is added into the cultivation wastewater through the wastewater pipeline (1 b), flocculation and precipitation of the cultivation wastewater are completed in the filter tank (3), suspended particles are removed through a grid device (3 a), and the pretreated cultivation wastewater enters a forward osmosis concentration unit for continuous treatment;
b) The method comprises the steps of forward osmosis concentration of the culture wastewater, pumping pretreated culture wastewater into a raw material liquid side of a liquid-extract forward osmosis membrane device (4) through a second water pump (3 b), pumping concentrated seawater with the concentration of 20-25% in a liquid-extract slurry preparation tank (5) into a liquid-extract side of a liquid-extract forward osmosis membrane component (4) as liquid-extract by a first liquid-extract pump (5 a), concentrating the salinity of the culture wastewater to 10-12% under the action of forward osmosis pressure, diluting the concentration of the liquid-extract to 12-15%, enabling a part of diluted liquid-extract to enter the liquid-extract preparation tank (5), adding sea salt into the liquid-extract for configuration and recycling, enabling the rest of concentrated culture wastewater to enter a sea water tank (13), and continuously treating by a forward osmosis ammonium recovery unit;
c) Recovering forward osmosis ammonium of the culture wastewater, enabling the concentrated culture wastewater to enter a raw material liquid side of a fertilizer drawing liquid forward osmosis membrane device (7), pumping a magnesium nitrate solution with the concentration of 14-16% in a magnesium nitrate drawing liquid pond (6) as drawing liquid into a drawing liquid side of a fertilizer drawing liquid forward osmosis membrane component (7) by a second drawing liquid pump (6 a), and under the action of osmotic pressure at two sides of a forward osmosis membrane, pumping NH in the culture wastewater 4 + And water molecules penetrate through the permeable membrane and enter the drawing liquid, the drawing liquid containing magnesium nitrate and ammonium ions enters a fertilizer pool (8) for farmland fertilizer, and a small amount of Mg in the magnesium nitrate drawing liquid 2+ Penetrating through the permeable membrane and entering into the culture wastewater, and concentrating for the second time to obtain a concentrated solution containing Mg 2+ 、PO 4 3- And NH 4 + The culture seawater enters a magnesium ammonium phosphate precipitation separation unit to carry out crystallization precipitation treatment;
d) Precipitation separation of magnesium ammonium phosphate in the culture wastewater, and feeding the culture seawater after secondary concentration into a stirring reactor (9), wherein Mg in the culture seawater 2+ 、PO 4 3- And NH 4 + And (3) carrying out chemical reaction in the stirring reactor (9) to generate magnesium ammonium phosphate precipitate, filtering the magnesium ammonium phosphate precipitate by a filter (10), enabling the magnesium ammonium phosphate precipitate to enter a centrifugal separator (11) from a solid discharge port for solid-liquid separation to obtain a crystalline magnesium ammonium phosphate solid fertilizer, returning part of the culture seawater after filtering and separating by the filter (10) to the stirring reactor (9) for continuous precipitation reaction, returning the other part of the culture seawater to a seawater tank (13), mixing the culture seawater with fresh seawater, and enabling the culture seawater to enter a seawater culture pond for repeated recycling.
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