Treatment method for cleaning waste liquid of liquid ammonia transportation tank

Abstract

The invention provides a method for treating cleaning waste liquid of a liquid ammonia transportation tank, and relates to the technical field of wastewater treatment. According to the method, the high-concentration ammonia nitrogen concentrated solution is generated through the forward osmosis-reverse osmosis synergistic technology, and the magnesium ammonium phosphate is generated through the subsequent chemical precipitation method, so that the influence of other pollutants such as suspended matters in the wastewater on the purity of the magnesium ammonium phosphate is reduced, and the purity of the magnesium ammonium phosphate is improved (greater than 90%). The method is suitable for ammonia-nitrogen wastewater with different concentrations, the deamination effect is good, secondary pollution is not generated, ammonia nitrogen can be converted into high-purity magnesium ammonium phosphate, magnesium ammonium phosphate can be used for slow release fertilizers, chemical additives and the like, and the method has good market prospects and subsequent utilization value.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a method for treating ammonia nitrogen wastewater. Background Art

[0002] Tank trucks are also called tank cars. Liquid ammonia is transported by tank trucks. Tank trucks need to be cleaned and inspected every year. Due to long-term use of sedimentation and corrosion of liquid ammonia, impurities will inevitably be generated on the inner wall of the tank truck. These impurities include a large amount of suspended matter, heavy metals and other pollutants. When cleaning, these impurities will be discharged from the tank truck with the flushing wastewater. At the same time, the wastewater also contains a large amount of ammonia nitrogen. How to deal with these wastewaters so that they do not harm the environment has become one of the main tasks of tank truck cleaning.

[0003] The biological method uses microorganisms to convert a series of organic nitrogen into ammonia nitrogen, and then converts ammonia nitrogen into nitrogen gas through the nitrification and denitrification of nitrifying bacteria and denitrifying bacteria to achieve the purpose of removing ammonia nitrogen. The biological method is suitable for the treatment of low-concentration ammonia nitrogen wastewater. It has the advantages of good deammonification effect, convenient operation, and no secondary pollutants. However, the survival and reproduction of bacteria have strict requirements on environmental conditions such as pH and temperature, and the deammonification cost is high.

[0004] The stripping method uses the volatility of ammonia nitrogen. After the wastewater is adjusted to be alkaline, ammonia will dissociate and escape from the wastewater. The purpose of removing ammonia nitrogen from the wastewater can be achieved by blowing away the ammonia gas with air or steam. The stripping method is suitable for treating high-concentration ammonia nitrogen wastewater. It has the advantages of simple operation and stable operation, but it has the disadvantages of large air or steam consumption, high power consumption, high cost, poor production workshop operating environment, and high safety risks. Summary of the invention

[0005] The purpose of the present invention is to provide a method for treating waste liquid from cleaning ammonia transport tanks. The present invention is applicable to wastewater with ammonia nitrogen of different concentrations, has good deammoniation effect, does not generate secondary pollution, and can convert ammonia nitrogen into high-purity magnesium ammonium phosphate, which has extremely high utilization value.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for treating ammonia nitrogen wastewater, comprising the following steps:

[0008] Microfiltering the ammonia nitrogen wastewater to obtain a microfiltrate;

[0009] The microfiltrate is sequentially subjected to forward osmosis treatment and reverse osmosis treatment to obtain an ammonia nitrogen concentrated solution;

[0010] The pH value of the ammonia nitrogen concentrated solution is adjusted to 9.0-10.7, and then disodium hydrogen phosphate and magnesium chloride are added to the ammonia nitrogen concentrated solution with a pH value of 9.0-10.7 to carry out precipitation reaction to form magnesium ammonium phosphate precipitation, and then separate the solid and liquid.

[0011] Preferably, the ammonia nitrogen wastewater is coarsely filtered before the microfiltration.

[0012] Preferably, the ammonia nitrogen wastewater includes liquid ammonia tank truck cleaning wastewater.

[0013] Preferably, the microfiltration membrane used in the microfiltration is a polyethersulfone microfiltration membrane with a pore size of 0.22-0.45 μm.

[0014] Preferably, the osmotic membrane used in the forward osmosis treatment is Aquaporin HFFO2 module, water flux is 11±1.5LMH, specific salt flux is 0.15±0.05g / L, and the membrane material is polyamide film composite material.

[0015] Preferably, the reverse osmosis membrane used in the reverse osmosis treatment is Suez SE reverse osmosis membrane SE1812C-34D.

[0016] Preferably, the molar ratio of ammoniacal N in the ammonia nitrogen concentrated solution with a pH value of 9.0 to 10.7, P in disodium hydrogen phosphate and Mg in magnesium chloride is 1.0:1.4:1.1.

[0017] Preferably, the temperature of the precipitation reaction is 20-35°C.

[0018] Preferably, the precipitation reaction time is 30 to 70 minutes.

[0019] Preferably, the precipitation reaction is carried out under stirring conditions, and the stirring speed is 100-400 r / min.

[0020] The present invention provides a method for treating ammonia nitrogen wastewater, comprising the following steps: microfiltration of ammonia nitrogen wastewater to obtain microfiltrate; sequentially performing forward osmosis treatment and reverse osmosis treatment on the microfiltrate to obtain an ammonia nitrogen concentrated solution; adjusting the pH value of the ammonia nitrogen concentrated solution to 9.0-10.7, and then adding disodium hydrogen phosphate and magnesium chloride to the obtained ammonia nitrogen concentrated solution with a pH value of 9.0-10.7 for precipitation reaction to form magnesium ammonium phosphate precipitation, and solid-liquid separation. The present invention produces a high-concentration ammonia nitrogen concentrated solution through forward osmosis-reverse osmosis synergistic technology, and subsequently performs a chemical precipitation method to produce magnesium ammonium phosphate, thereby reducing the influence of other pollutants such as suspended matter in wastewater on the purity of magnesium ammonium phosphate, and improving the purity of magnesium ammonium phosphate (>90%).

[0021] The present invention is applicable to ammonia nitrogen wastewater with different concentrations, has good deammoniation effect, does not generate secondary pollution, and can convert ammonia nitrogen into high-purity magnesium ammonium phosphate. Magnesium ammonium phosphate can be used for slow-release fertilizers, chemical additives, etc., and has good market prospects and subsequent utilization value. DETAILED DESCRIPTION

[0022] The present invention provides a method for treating ammonia nitrogen wastewater, comprising the following steps:

[0023] Microfiltering the ammonia nitrogen wastewater to obtain a microfiltrate;

[0024] The microfiltrate is sequentially subjected to forward osmosis treatment and reverse osmosis treatment to obtain an ammonia nitrogen concentrated solution;

[0025] The pH value of the ammonia nitrogen concentrated solution is adjusted to 9.0-10.7, and then disodium hydrogen phosphate and magnesium chloride are added to the ammonia nitrogen concentrated solution with a pH value of 9.0-10.7 to carry out precipitation reaction to form magnesium ammonium phosphate precipitation, and then separate the solid and liquid.

[0026] In the present invention, unless otherwise specified, the raw materials and equipment used are commercially available products well known in the art.

[0027] The invention microfilters ammonia nitrogen wastewater to obtain microfiltrate.

[0028] In the present invention, the ammonia nitrogen wastewater preferably includes liquid ammonia tank truck cleaning wastewater; the present invention has no special requirements on the concentration of ammonia nitrogen in the ammonia nitrogen wastewater, and any concentration is applicable to the present invention.

[0029] Before the microfiltration, the present invention preferably performs coarse filtration on the ammonia nitrogen wastewater.

[0030] The present invention does not make any special requirements on the specific implementation process of the coarse filtration, and any coarse filtration process known in the art can be used. The present invention utilizes coarse filtration to preliminarily remove solid particles.

[0031] In the present invention, the microfiltration membrane used for microfiltration is preferably a polyethersulfone microfiltration membrane, and the pore size is preferably 0.22-0.45 μm. In the embodiment of the present invention, two microfiltration membranes are specifically used, and the microfiltration membrane adopts the Xingda brand microfiltration membrane, and the membrane pore sizes are 0.45 μm and 0.22 μm respectively, and the membrane area is 0.23 m 2 The membrane shell is made of 304 stainless steel, and the membrane material is polyethersulfone (PES) microfiltration membrane. The present invention further removes solid particles through microfiltration.

[0032] After obtaining the microfiltrate, the present invention sequentially performs forward osmosis treatment and reverse osmosis treatment on the microfiltrate to obtain an ammonia nitrogen concentrated solution.

[0033] In the present invention, the osmotic membrane used in the forward osmosis treatment is preferably commercially available Aquaporin HFFO2 module, specifically: water flux is 11±1.5LMH, specific salt flux is 0.15±0.05g / L, membrane material is polyamide film composite material, membrane area is 2.3m 2 The present invention utilizes the driving force caused by the osmotic pressure difference between the microfiltrate and the forward osmosis draw liquid to retain the pollutants in the microfiltrate on one side of the membrane, and then water flows into the draw liquid through the membrane to dilute the draw liquid. Through the continuous forward osmosis process, the substances in the wastewater are continuously retained and the microfiltrate is continuously concentrated.

[0034] In the present invention, the reverse osmosis membrane used in the reverse osmosis treatment is preferably the commercially available Suez SE reverse osmosis membrane SE1812C-34D, specifically: the membrane area is 0.32m 2 The average NaCl rejection rate is 98.5%, the minimum NaCl rejection rate is 97.5%, and the membrane material is TFM (thin layer composite membrane: a patented film layer of SUEZ-WTS is inserted between the polyamide film layer (PA) and the polysulfone layer (PS)). The present invention regenerates the draw liquid through the reverse osmosis process, so that the draw liquid concentration returns to the initial concentration, maintains a large driving force to maintain the water flux set by the forward osmosis process, and then the reverse osmosis process recovers the clean water.

[0035] The present invention can efficiently concentrate the ammonia nitrogen content through the forward osmosis-reverse osmosis synergistic technology, is applicable to wastewaters with ammonia nitrogen of different concentrations, and simultaneously reduces the influence of other pollutants such as suspended matter in the wastewater on the purity of the subsequently generated magnesium ammonium phosphate precipitate.

[0036] After obtaining the ammonia nitrogen concentrated solution, the present invention adjusts the pH value of the ammonia nitrogen concentrated solution to 9.0-10.7, then adds disodium hydrogen phosphate and magnesium chloride to the obtained ammonia nitrogen concentrated solution with a pH value of 9.0-10.7 for precipitation reaction to form magnesium ammonium phosphate precipitation, and separates the solid from the liquid.

[0037] In the present invention, NaOH is preferably used to adjust the pH value of the ammonia nitrogen concentrate to 9.0 to 10.7, more preferably 9.5 to 10.0. Magnesium ammonium phosphate reacts easily with H under acidic conditions. + Therefore, when using the magnesium ammonium phosphate precipitation method, the pH value cannot be too low and should be operated in an alkaline environment. In theory, as the pH value gradually increases, more visible white crystals will precipitate, and the effect of recovering ammonia nitrogen will be better. However, according to research, when the pH value exceeds a certain limit, Mg3(PO4)2, which is more difficult to dissolve in water, will be generated, and it will corrode pipelines and equipment to a certain extent, resulting in increased subsequent operating costs. At the same time, too high a pH value requires the consumption of a large amount of NaOH, and the cost of the drugs used will increase accordingly, which is not economical. Therefore, the pH value of ammonia nitrogen concentrate is 9.0-10.7.

[0038] In the present invention, the molar ratio of ammoniacal N in the ammonia nitrogen concentrated solution with a pH value of 9.0 to 10.7, P in disodium hydrogen phosphate and Mg in magnesium chloride is preferably 1.0:1.4:1.1.

[0039] In the present invention, the temperature of the precipitation reaction is preferably 20-35° C.; the time of the precipitation reaction is preferably 30-70 min, more preferably 50 min.

[0040] The present invention is beneficial to improving the purity of magnesium ammonium phosphate precipitation by controlling the molar ratio of N, P and Mg within the above range as well as the temperature and time of the reaction, and the high-purity magnesium ammonium phosphate has a higher application value.

[0041] In the present invention, the precipitation reaction is preferably carried out under stirring conditions, and the stirring speed is preferably 100 to 400 r / min.

[0042] The present invention has no special requirements for the solid-liquid separation method, and any solid-liquid separation method known in the art can be used.

[0043] The following is a detailed description of the method for treating the cleaning waste liquid of the liquid ammonia transport tank provided by the present invention in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0044] Example 1

[0045] The liquid ammonia tank truck cleaning wastewater (water quality indicators are shown in Table 1) was coarsely filtered, and the coarse filtered wastewater and ammonia nitrogen wastewater were microfiltered. Specifically, two microfiltration membranes were used. The microfiltration membranes were Xingda brand microfiltration membranes with pore sizes of 0.45 μm and 0.22 μm, respectively, and membrane areas of 0.23 m 2 , the membrane shell is made of 304 stainless steel, and the membrane material is polyethersulfone (PES) microfiltration membrane to obtain microfiltrate;

[0046] The microfiltrate is sequentially subjected to forward osmosis treatment and reverse osmosis treatment, and the forward osmosis membrane is Aquaporin HFFO2 module, the reverse osmosis membrane is Suez SE reverse osmosis membrane SE1812C-34D, and ammonia nitrogen concentrate is obtained;

[0047] The pH value of the ammonia nitrogen concentrate was adjusted to 9.5 and the temperature was 35° C. Then, disodium hydrogen phosphate and magnesium chloride were added to the ammonia nitrogen concentrate with a pH value of 9.5, and the molar ratio of N, P and Mg was 1.0:1.4:1.1. The mixture was stirred for 50 min at a stirring speed of 100 r / min to form magnesium ammonium phosphate precipitate. The solid-liquid separation was performed to obtain magnesium ammonium phosphate as a slow-release fertilizer and treated wastewater (water quality indicators are shown in Table 2).

[0048] Table 1 Water quality indicators of liquid ammonia tanker cleaning wastewater

[0049] parameter Sample content method Detection limit SS (suspended solids) 511mg / L GB / T11901-1989 / BOD 50.0mg / L HJ505-2009 0.5mg / L COD (Chemical Oxygen Demand) 128mg / L HJ828-2017 4mg / L TN (Total Nitrogen) 96.5mg / L HJ636-2012 0.05mg / L Turbidity 167.6NTU HJ1075-2019 0.3NTU Total dissolved solids 1482mg / L GB / T5750.4-2023 / Petroleum 17.7mg / L HJ637-2018 0.06mg / L pH 10.02 HJ1147-2020 /

[0050] Table 2 Water quality of liquid ammonia tanker cleaning wastewater after treatment

[0051] parameter Sample content method Detection limit SS (suspended solids) 30mg / L GB / T11901-1989 / BOD 20.0mg / L HJ505-2009 0.5mg / L COD (Chemical Oxygen Demand) 18mg / L HJ828-2017 4mg / L TN (Total Nitrogen) 8.4mg / L HJ636-2012 0.05mg / L Turbidity 10NTU HJ1075-2019 0.3NTU Total dissolved solids 58mg / L GB / T5750.4-2023 / Petroleum 6mg / L HJ637-2018 0.06mg / L pH 9.5 HJ1147-2020 /

[0052] It can be seen from the data in Table 1 and Table 2 that after being treated by the method of the present invention, the ammonia nitrogen removal rate can reach 91.30%, the water purification effect is good, and the content of magnesium ammonium phosphate in the obtained precipitate is as high as 90.57%, which has good recycling value.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for treating ammonia nitrogen wastewater, characterized in that: The following steps are involved: Microfiltering the ammonia nitrogen wastewater to obtain a microfiltrate; The microfiltrate is sequentially subjected to forward osmosis treatment and reverse osmosis treatment to obtain an ammonia nitrogen concentrated solution; The pH value of the ammonia nitrogen concentrated solution is adjusted to 9.0-10.7, and then disodium hydrogen phosphate and magnesium chloride are added to the ammonia nitrogen concentrated solution with a pH value of 9.0-10.7 to carry out precipitation reaction to form magnesium ammonium phosphate precipitation, and then separate the solid and liquid.

2. The processing method according to claim 1, characterized in that: The method also includes coarse filtration of the ammonia nitrogen wastewater before the microfiltration.

3. The processing method according to claim 1 or 2, characterized in that: The ammonia nitrogen wastewater includes liquid ammonia tank truck cleaning wastewater.

4. The processing method according to claim 1, characterized in that: The microfiltration membrane used in the microfiltration is a polyethersulfone microfiltration membrane with a pore size of 0.22-0.45 μm.

5. The processing method according to claim 1, characterized in that: The osmotic membrane used in the forward osmosis treatment is Aquaporin HFFO2 module, water flux is 11±1.5LMH, specific salt flux is 0.15±0.05g / L, and the membrane material is polyamide film composite material.

6. The processing method according to claim 1, characterized in that: The reverse osmosis membrane used in the reverse osmosis treatment is Suez SE reverse osmosis membrane SE1812C-34D.

7. The processing method according to claim 1, characterized in that: The molar ratio of ammoniacal N in the ammonia nitrogen concentrated solution with a pH value of 9.0 to 10.7, P in disodium hydrogen phosphate and Mg in magnesium chloride is 1.0:1.4:1.

1.

8. The processing method according to claim 1, characterized in that: The temperature of the precipitation reaction is 20-35°C.

9. The processing method according to claim 1, characterized in that: The precipitation reaction time is 30 to 70 minutes.

10. The processing method according to claim 1, 8 or 9, characterized in that: The precipitation reaction is carried out under stirring conditions, and the stirring speed is 100-400r / min.