CN114314924A - Method for treating wastewater in tunnel construction period - Google Patents
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Abstract
A method for treating wastewater in a tunnel construction period comprises the following steps: step 1, performing solid-liquid separation, namely adding a coagulant into the wastewater, and fully reacting to form smaller flocs to obtain first treated water; adding a flocculating agent into the first treated water to form large and compact flocs and obtain second treated water; performing solid-liquid separation on the second treated water to obtain supernatant as third treated water; step 2, neutralization flocculation, wherein neutralization rough filtration is carried out on the third treated water, flocs which are not completely precipitated in the third treated water are further filtered, and primary pH adjustment is carried out to obtain fourth treated water; performing neutralization flocculation on the fourth treated water, mixing medical stone fine powder with oxalic acid, adding into the fourth treated water, performing secondary pH adjustment and micro flocculation on the fourth treated water, and performing full reaction to obtain fifth treated water; and 3, filtering and adsorbing, wherein the fifth treated water passes through a screen and a multilayer filter material consisting of quartz sand and activated carbon to obtain final effluent.
Description
Technical Field
The invention belongs to the technical field of sewage treatment, and particularly relates to a method for treating wastewater in a tunnel construction period.
Background
The proportion of tunnel engineering in mountainous or heavily-hilled areas is increasing day by day, the problem of ecological environment pollution caused by tunnel construction waste water generated by tunnel construction is attracting attention gradually, in recent years, along with the development of green construction and the strict of ecological environment protection standards, the attention and investment for treating tunnel construction waste water are increased year by year for each railway tunnel construction project, and the proper treatment of tunnel construction waste water is of great importance for protecting the surrounding environment along the railway.
At present, railway tunnel construction mainly adopts two types, namely an explosion method and a TBM method, wastewater generated in the construction process mainly comes from gushing water generated when a railway tunnel passes through a bad geological unit, wastewater generated by tunnel construction machinery, wastewater for dust fall after explosion, and wastewater generated by concrete spraying and grouting, and indexes of main pollutants in the construction wastewater are Ca, Mg ions and the like caused by the gushing water under pH, SS, ammonia nitrogen, COD, petroleum and special geological conditions. A large amount of literature research data show that the problems that pollution factors mainly exceeding the standard are SS and the pH value exceeds the standard in the railway tunnel construction wastewater are prominent.
At present, for the turbid wastewater containing SS, the main treatment methods comprise the technologies of flocculant coagulant aid, coagulating sedimentation, air flotation, micro-flocculation filtration, medium loading flocculation, high-efficiency clarification and the like, and large-particle suspended matters can be removed by the technical means; however, the suspended matter in the tunnel construction wastewater is inorganic particles, the content, the particle size and the surface physicochemical property are related to tunnel lithology and construction method, and the dust which is low in turbidity or fine in special lithology and difficult to settle is difficult to effectively treat. Aiming at the treatment of low-turbidity wastewater, the micro-flocculation reaction time is shorter, and the micro-flocculation reaction time is an option of a tunnel wastewater treatment process with low turbidity and fine suspended matter pollution, but the micro-flocculation is rarely applied to tunnel construction wastewater treatment at present.
For the problem that the pH value of tunnel wastewater exceeds the standard, inorganic acids such as sulfuric acid and hydrochloric acid are often adopted for neutralization adjustment, the use is limited due to control, railway tunnel construction is often in mountainous areas, the transportation condition is inconvenient, the treatment cost and medicament storage risk are greatly increased by adopting a large amount of inorganic acids such as sulfuric acid and hydrochloric acid for pH adjustment, and the procedure is complex. Therefore, a treatment method is needed to ensure that the pH of the tunnel construction wastewater effluent can reach the discharge standard more safely and economically.
Patent document CN104310658B discloses a tunnel sewage treatment device, which comprises a primary sedimentation tank for primary filtration of sewage, an organic matter treatment tank for decomposing and removing organic matters in sewage, a tertiary sedimentation tank for further filtration of sewage, and a water collecting tank for collecting water after purification treatment, in sequence according to the advancing direction of water flow, wherein a plurality of different decontamination tanks are arranged to pertinently filter, remove impurities, remove oil and adjust the pH value of sewage. However, fine dust particles which are difficult to settle in water cannot be efficiently removed only by methods such as natural precipitation, gauze filtration, plate blocking removal, flocculant addition or mechanical filtration treatment (a centrifugal machine or an air flotation machine) and the like, and suspended matters in the effluent are difficult to reach the standard.
Patent document CN108275801B discloses a tunnel construction wastewater treatment process, which improves the treatment speed and treatment effect of tunnel construction wastewater through primary natural sedimentation treatment, pre-flocculation post-coagulation treatment, secondary natural sedimentation treatment, sludge concentration treatment, and sludge dewatering treatment, wherein the pre-flocculation post-coagulation adopts ABC medicament combination (a medicament is flocculant polyaluminum chloride, B medicament is coagulant aid polyacrylamide, and C medicament is pH regulator), the removal of suspended matters and pH adjustment are performed by adding a flocculant, a coagulant aid, and a pH regulator at one time, but the medicament consumption is large, and the secondary natural sedimentation can be performed only after the sediments and particles in water are flocculated into larger groups, and the reaction time is longer.
Generally speaking, tunnel construction waste water has tiny suspended solid to handle the difficulty and the pH is handled the difficulty at present, and the processing cost of both and the long problem of handling duration.
Therefore, a method for treating wastewater during tunnel construction needs to be designed.
Disclosure of Invention
The invention aims to provide a method for treating wastewater in a tunnel construction period, which aims to solve the problems that the prior tunnel construction wastewater in the background art is difficult to treat fine suspended matters and pH, and the treatment cost and the treatment time of the two are long.
In order to achieve the aim, the invention provides a method for treating wastewater in a tunnel construction period, which comprises the following steps:
step 1, performing solid-liquid separation, namely adding a coagulant into the tunnel construction wastewater to ensure that the wastewater and the coagulant are fully reacted through rapid stirring, and the coagulant and suspended matters in the wastewater form small flocs to obtain first treated water; adding a flocculating agent into the first treated water, and further combining suspended matters and flocs in the wastewater through slow stirring to form large and compact flocs to obtain second treated water; performing solid-liquid separation on the second treated water to obtain supernatant as third treated water;
step 2, neutralization flocculation, wherein neutralization rough filtration is carried out on the third treated water, flocs which are not completely precipitated in the third treated water are further filtered through a double-layer medical stone combined filler, and primary pH adjustment is carried out to obtain fourth treated water; performing neutralization flocculation on the fourth treated water, mixing medical stone fine powder with oxalic acid, adding into the fourth treated water, performing secondary pH adjustment and micro flocculation on the fourth treated water, and performing full reaction to obtain fifth treated water;
and 3, filtering and adsorbing, namely filtering and adsorbing the fifth treated water by using a screen and a multilayer filter material consisting of quartz sand and activated carbon, recovering medical stone fine powder in the fifth treated water by filtering and adsorbing, and removing calcium oxalate precipitates, micro flocculates and COD (chemical oxygen demand) which possibly exceeds the standard due to the addition of organic acid in the fifth treated water to obtain final effluent.
In a specific embodiment, in the step 1, the coagulant added is one or more of polyaluminium chloride, polyaluminium sulfate, polyferric sulfate, ferrous sulfate and aluminium sulfate, the stirring speed of the rapid stirring is 150-.
In a specific embodiment, in the step 1, the added flocculant is polyacrylamide, the stirring speed of the slow stirring is 50-100r/min, and the reaction time after the flocculant is added is 2-10 min.
In a specific embodiment, in the step 1, the solid-liquid separation mode is one or more of precipitation, centrifugal separation, filtration and air flotation.
In a specific embodiment, in the step 2, the two layers of medical stone combined fillers comprise a layer of medical stone filler with the particle size of 1-3mm and a layer of medical stone filler with the particle size of 0.5-1mm, the two layers of medical stone fillers are separated by layers through a perforated partition plate or a screen with the pore diameter smaller than 0.5mm, and the filling volume ratio of the two layers of medical stone fillers is 1: 10-20.
In a specific embodiment, in the step 2, the contact time of the wastewater and the medical stone filler with the particle size of 1-3mm is 5-8min, the contact time of the wastewater and the medical stone filler with the particle size of 0.5-1mm is 50-160min, and flocs which are not completely removed after solid-liquid separation of coagulating sedimentation are removed through step filtration and pH adjustment of the medical stone fillers with different particle sizes, so that the pH adjustment effect is enhanced.
In a specific embodiment, in the step 2, medical stone fine powder with the particle size of 0.05mm-0.08mm is added during the neutralization flocculation, and the adding amount is 100-500mg/L wastewater; the time for the fourth treated water to carry out neutralization flocculation reaction is 1-5min, and the stirring speed during the reaction is 100-200 r/min.
In a specific embodiment, the step 2 further comprises performing pH measurement on the fourth treated water to determine the adding amount of the oxalic acid, so that the pH of the fifth treated water and the final effluent reaches 6-9.
In a specific embodiment, in the step 3, the filtration speed of the adsorption filtration is 5-10m/h, the aperture of the screen mesh is less than 0.05mm, the particle size of the quartz sand is 1-2mm, and the thickness of the filtration layer of the multi-layer filtration material is 0.2-1 m.
In a specific embodiment, in the step 3, the particle size of the activated carbon is preferably 0.2-0.8mm, and the thickness of the filter layer of the multi-layer filter material is preferably 0.2-0.5 m.
Compared with the prior art, the invention has the following beneficial effects:
(1) through the regulation of medical stone and oxalic acid, the alkalinity of the tunnel construction wastewater is reduced, inorganic strong acid such as sulfuric acid, hydrochloric acid and the like is not required to be added, and the field management is safer and more convenient.
(2) Through primary coagulation flocculation, secondary micro flocculation and graded flocculation, the secondary micro flocculation is based on components with flocculation effect such as silicon, aluminum and the like in medical stone and calcium ions contained in oxalic acid and tunnel wastewater, calcium oxalate precipitation can be generated, various coagulants and organic flocculants do not need to be added again, and the adding amount of the coagulants and the flocculants is reduced.
(3) The recycled medical stone fine powder can also play a role in filtration, and part of the medical stone fine powder can be recycled to the step of mixing with calcium oxalate to be used as a flocculant source for recycling.
(4) The treatment of two main overproof indexes SS and pH in tunnel construction wastewater is more thorough, the hardness in the wastewater can be reduced by calcium oxalate precipitation, and pollutants such as ammonia nitrogen, total phosphorus, heavy metals, COD and the like which possibly exist in the wastewater can be reduced by coagulation, micro flocculation and adsorption of medical stone, quartz sand and activated carbon.
In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below.
Detailed Description
The present invention will be described in detail with reference to specific examples, which are provided for illustration only and are not intended to limit the invention.
The invention relates to a method for treating wastewater in a tunnel construction period, which comprises the following steps:
step 1: and (4) solid-liquid separation.
Adding one or more of a certain amount of polyaluminium chloride solution, polyaluminium sulfate solution, polyferric sulfate solution, ferrous sulfate solution and aluminum sulfate solution into the tunnel construction wastewater as a coagulant, rapidly stirring at a stirring speed of 150-;
adding a certain amount of polyacrylamide solution as a flocculating agent into the first treated water, and stirring at a low speed of 50-100r/min for 2-10min to fully combine most suspended matters in the wastewater with flocs to form large and compact flocs to obtain second treated water;
and carrying out solid-liquid separation on the flocs and the wastewater by one or more of precipitation, centrifugal separation, filtration and air flotation on the second treated water to obtain supernatant which is third treated water.
Step 2: neutralizing and flocculating.
Neutralizing and coarse-filtering the third treated water by using a combined double-layer filler with a filling volume ratio of 1:10-1:20, and firstly, performing contact filtration for 5-8min by using a filler layer with a particle size of 1-3 mm; then passing through a filler layer with the particle size of 0.5-1mm, and performing contact filtration for 50-160 min; further filtering the incompletely precipitated flocs in the third treated water, and carrying out primary pH adjustment to obtain fourth treated water;
and (2) performing neutralization flocculation on the fourth treated water, mixing medical stone fine powder with the particle size of 0.05-0.08 mm with an oxalic acid solution, adding the mixture into the fourth treated water to ensure that the content of the medical stone fine powder in the fourth treated water is 100-500mg/L, reacting for 1-5min under the condition that the stirring speed is 100-200r/min, and performing secondary pH adjustment and micro flocculation on the fourth treated water until the pH of the effluent reaches 6-9 to obtain fifth treated water.
And step 3: and (5) filtering and adsorbing.
And the fifth treated water sequentially passes through a screen with the aperture smaller than 0.05mm, a quartz sand filter layer with the thickness of 0.5-1m and the particle size of 1-2mm and an active carbon filter layer with the thickness of 0.2-0.5m and the particle size of 0.2-0.8mm at the filtering speed of 5-10m/h, medical stone fine powder in the fifth treated water is intercepted and recovered through the screen, calcium oxalate precipitates, micro flocculates and COD which is possibly out of standard due to the addition of organic acid are removed through filtration and adsorption recovery, and the final effluent is obtained.
Example 1
Taking 1L of wastewater in a certain tunnel construction period, and measuring that the SS content in the wastewater is 3668mg/L, the pH value is 12.5, the calcium ion content is 171mg/L, the ammonia nitrogen content is 2.08mg/L, the COD concentration is 16mg/L, and the total phosphorus is 0.22 mg/L.
And (4) solid-liquid separation. Adding 50mg/L of polyaluminum chloride into the wastewater, stirring for 1min at 200r/min, uniformly mixing the medicament and the wastewater, adding 3mg/L of polyacrylamide, stirring for 3min at 80r/min, uniformly mixing the medicament and the wastewater, and precipitating for 4min to obtain a supernatant.
Neutralizing and flocculating. And (3) sequentially passing the supernatant obtained by solid-liquid separation through a medical stone filler layer with the particle size of 1.5-2mm and a medical stone filler layer with the particle size of 0.6-0.8mm according to the filling volume ratio of 1:12 for neutralization and rough filtration, and controlling the contact time of the two filler layers to be 5min and 1h respectively. Adding a mixed solution of medical stone fine powder with the particle size of 0.08mm and oxalic acid into the effluent after the neutralization and rough filtration, controlling the adding amount of the medical stone and the adding amount of the oxalic acid in the wastewater to be 120mg and 600mg, and stirring and reacting for 5min at the stirring speed of 150 r/min.
And (5) filtering and adsorbing. The neutralized and flocculated effluent sequentially passes through a screen with the aperture of 0.05mm, a quartz sand filtering layer with the thickness of 0.5m and the thickness of 1-2mm and an active carbon filtering layer with the thickness of 0.2m and the thickness of 0.5-0.8mm at the filtering speed of 6m/h to obtain the final effluent.
The SS content of the final effluent is 24mg/L, the pH value is 7.9, the calcium ion content is 12mg/L, the ammonia nitrogen content is 1.28mg/L, the COD concentration is 22mg/L, and the total phosphorus content is 0.12 mg/L.
Example 2
Taking 1L of wastewater in a certain tunnel construction period, and measuring that the SS content in the wastewater is 1288mg/L, the pH is 10.5, the calcium ion content is 181mg/L, the ammonia nitrogen content is 4.2mg/L, the COD concentration is 38mg/L, and the total phosphorus is 0.16 mg/L.
And (4) solid-liquid separation. Adding 20mg/L of polyaluminum chloride into the wastewater, stirring for 1min at 200r/min, uniformly mixing the medicament and the wastewater, adding 1.5mg/L of polyacrylamide, stirring for 3min at 60r/min, uniformly mixing the medicament and the wastewater, and precipitating for 5min to obtain supernatant.
Neutralizing and flocculating. And (3) sequentially passing the supernatant obtained by solid-liquid separation through a medical stone filler layer with the particle size of 1.5-2mm and a medical stone filler layer with the particle size of 0.6-0.8mm according to the filling volume ratio of 1:10 for neutralization and rough filtration, and controlling the contact time of the two filler layers to be 5min and 50min respectively. Adding mixed solution of Maifanitum fine powder with particle size of 0.08mm and oxalic acid into the neutralized and coarsely-filtered effluent, controlling the adding amount of Maifanitum to be 100mg and the adding amount of oxalic acid to be 200mg, and stirring at a stirring speed of 150r/min for reaction for 5 min.
And (5) filtering and adsorbing. And (3) sequentially passing the neutralized and flocculated effluent through a screen with the aperture of 0.05mm, a quartz sand filter layer with the thickness of 0.5m and the particle size of 1-2mm and an activated carbon filter layer with the thickness of 0.2m and the particle size of 0.5-0.8mm at the filtering speed of 6m/h to obtain the final effluent.
The SS content of the final effluent is 18mg/L, the pH value is 7.2, the calcium ion content is 18mg/L, the ammonia nitrogen content is 1.14mg/L, the COD concentration is 4mg/L, and the total phosphorus content is 0.1 mg/L.
Example 3
Taking 1L of wastewater in a certain tunnel construction period, and measuring that the SS content in the wastewater is 362mg/L, the pH value is 12.9, the calcium ion content is 32mg/L, and the COD content is 13 mg/L.
And (4) solid-liquid separation. Adding 12mg/L of polyaluminium chloride into the wastewater, stirring for 1min at 200r/min, uniformly mixing the medicament and the wastewater, adding 1.5mg/L of polyacrylamide, stirring for 2min at 60r/min, uniformly mixing the medicament and the wastewater, and precipitating for 5min to obtain supernatant.
Neutralizing and flocculating. And (3) sequentially passing the supernatant obtained by solid-liquid separation through a medical stone filler layer with the particle size of 1.5-2mm and a medical stone filler layer with the particle size of 0.6-0.8mm according to the filling volume ratio of 1:10 for neutralization and rough filtration, and controlling the contact time of the two filler layers to be 5min and 50min respectively. Adding mixed solution of Maifanitum fine powder with particle size of 0.08mm and oxalic acid into the neutralized and coarsely-filtered effluent, controlling the adding amount of Maifanitum to be 100mg and the adding amount of oxalic acid to be 200mg, and stirring at a stirring speed of 150r/min for reaction for 5 min.
And (5) filtering and adsorbing. And (3) sequentially passing the neutralized and flocculated effluent through a screen with the aperture of 0.05mm, a quartz sand filter layer with the thickness of 0.5m and the particle size of 1-2mm and an active carbon filter layer with the thickness of 0.2m and the particle size of 0.5-0.8mm at the filtering speed of 6m/h to obtain the final effluent.
The SS content of the final effluent is 4mg/L, the pH value is 8.1, the calcium ion content is 0.05mg/L, and the COD concentration is 32 mg/L.
Comparative example 1
Taking 1L of wastewater in a certain tunnel construction period, and measuring that the SS content in the wastewater is 3668mg/L, the pH value is 12.5, the calcium ion content is 171mg/L, the ammonia nitrogen content is 2.08mg/L, the COD concentration is 16mg/L, and the total phosphorus is 0.22 mg/L.
Adding 50mg/L of polyaluminum chloride into the wastewater, stirring for 1min at 200r/min, uniformly mixing the medicament and the wastewater, adding 3mg/L of polyacrylamide, stirring for 3min at 80r/min, uniformly mixing the medicament and the wastewater, precipitating for 4min, and obtaining supernatant as effluent.
The SS content of the effluent is 172mg/L, the pH value is 10.8, the calcium ion content is 166mg/L, the ammonia nitrogen content is 2.48mg/L, the COD concentration is 14mg/L, and the total phosphorus content is 0.14 mg/L.
Comparative example 2
Taking 1L of wastewater in a certain tunnel construction period, and measuring that the SS content in the wastewater is 3668mg/L, the pH value is 12.5, the calcium ion content is 171mg/L, the ammonia nitrogen content is 2.08mg/L, the COD concentration is 16mg/L, and the total phosphorus is 0.22 mg/L.
Adding 50mg/L of polyaluminum chloride into the wastewater, stirring for 1min at 200r/min, uniformly mixing the medicament and the wastewater, adding 3mg/L of polyacrylamide, stirring for 3min at 80r/min, uniformly mixing the medicament and the wastewater, and precipitating for 4min to obtain a supernatant.
Adding 600mg of oxalic acid into the supernatant for pH adjustment, and stirring and reacting at a stirring speed of 150r/min for 5min to obtain final effluent.
The SS content of the effluent is 148mg/L, the pH value is 9.6, the calcium ion content is 16mg/L, the ammonia nitrogen content is 1.77mg/L, the COD concentration is 88mg/L, and the total phosphorus content is 0.16 mg/L.
Comparative example 3
Taking 1L of wastewater in a certain tunnel construction period, and measuring that the SS content in the wastewater is 3668mg/L, the pH value is 12.5, the calcium ion content is 171mg/L, the ammonia nitrogen content is 2.08mg/L, the COD concentration is 16mg/L, and the total phosphorus is 0.22 mg/L.
Adding 50mg/L of polyaluminum chloride into the wastewater, stirring for 1min at 200r/min, uniformly mixing the medicament and the wastewater, adding 3mg/L of polyacrylamide, stirring for 3min at 80r/min, uniformly mixing the medicament and the wastewater, and precipitating for 4min to obtain a supernatant.
Adding 12mg/L of polyaluminium chloride into the supernatant, stirring for 1min at 200r/min to uniformly mix the medicament with the wastewater, adding 2mg/L of polyacrylamide, stirring for 5min at 80r/min, and filtering at a filtering speed of 6m/h sequentially through a 1-2mm quartz sand filtering layer with the thickness of 0.5m and a 0.5-0.8mm active carbon filtering layer with the thickness of 0.2 m.
Adding 1500mg of oxalic acid into the filtrate for pH adjustment, and stirring and reacting at a stirring speed of 150r/min for 5min to obtain final effluent.
The SS content of the effluent is 76mg/L, the pH value is 8.8, the calcium ion content is 6mg/L, the ammonia nitrogen content is 1.96mg/L, the COD concentration is 115mg/L, and the total phosphorus content is 0.12 mg/L.
Comparative example 4
Taking 1L of wastewater in a certain tunnel construction period, and measuring that the SS content in the wastewater is 3668mg/L, the pH value is 12.5, the calcium ion content is 171mg/L, the ammonia nitrogen content is 2.08mg/L, the COD concentration is 16mg/L, and the total phosphorus is 0.22 mg/L.
Adding 50mg/L of polyaluminum chloride into the wastewater, stirring for 1min at 200r/min, uniformly mixing the medicament and the wastewater, adding 3mg/L of polyacrylamide, stirring for 3min at 80r/min, uniformly mixing the medicament and the wastewater, and precipitating for 4min to obtain a supernatant.
And (3) sequentially passing the supernatant obtained by solid-liquid separation through a medical stone filler layer with the particle size of 1.5-2mm and a medical stone filler layer with the particle size of 0.6-0.8mm according to the filling volume ratio of 1:12 for neutralization and rough filtration, and controlling the contact time of the two filler layers to be 5min and 1h respectively. Adding Maifanitum fine powder with particle diameter of 0.08mm into the neutralized and coarsely-filtered effluent, controlling the adding amount of Maifanitum in wastewater to be 120mg, and stirring at 150r/min for reaction for 5 min.
And (5) filtering and adsorbing. The neutralized and flocculated effluent sequentially passes through a screen with the aperture of 0.05mm, a quartz sand filtering layer with the thickness of 0.5m and the thickness of 1-2mm and an active carbon filtering layer with the thickness of 0.2m and the thickness of 0.5-0.8mm at the filtering speed of 6m/h to obtain the final effluent.
The SS content of the final effluent is 86mg/L, the pH value is 10.1, the calcium ion content is 158mg/L, the ammonia nitrogen content is 1.15mg/L, the COD concentration is 8mg/L, and the total phosphorus content is 0.14 mg/L.
As can be seen from the analysis of the above examples and comparative examples, the SS content of the effluent treated by the example for treating wastewater according to the invention is significantly lower than that of the treated by the comparative example, and the pH value of the treated wastewater by the example for treating wastewater according to the invention is closer to neutral than that of the comparative example.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions and substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (10)
1. A method for treating waste water in a tunnel construction period is characterized by comprising the following steps:
step 1, performing solid-liquid separation, namely adding a coagulant into the tunnel construction wastewater to ensure that the wastewater and the coagulant are fully reacted through rapid stirring, and the coagulant and suspended matters in the wastewater form small flocs to obtain first treated water; adding a flocculating agent into the first treated water, and further combining suspended matters and flocs in the wastewater through slow stirring to form large and compact flocs to obtain second treated water; performing solid-liquid separation on the second treated water to obtain supernatant as third treated water;
step 2, neutralization flocculation, wherein neutralization rough filtration is carried out on the third treated water, flocs which are not completely precipitated in the third treated water are further filtered through a double-layer medical stone combined filler, and primary pH adjustment is carried out to obtain fourth treated water; performing neutralization flocculation on the fourth treated water, mixing medical stone fine powder with oxalic acid, adding into the fourth treated water, performing secondary pH adjustment and micro flocculation on the fourth treated water, and performing full reaction to obtain fifth treated water;
and 3, filtering and adsorbing, namely filtering and adsorbing the fifth treated water by using a screen and a multilayer filter material consisting of quartz sand and activated carbon, recovering medical stone fine powder in the fifth treated water by filtering and adsorbing, and removing calcium oxalate precipitates, micro flocculates and COD (chemical oxygen demand) which possibly exceeds the standard due to the addition of organic acid in the fifth treated water to obtain final effluent.
2. The method for treating wastewater during tunnel construction according to claim 1, wherein in step 1, the coagulant is one or more of polyaluminium chloride, polyaluminium sulfate, polyferric sulfate, ferrous sulfate and aluminium sulfate, the stirring speed of the rapid stirring is 150-300r/min, and the reaction time of the rapid stirring after the coagulant is added is 0.5-3 min.
3. The method for treating the wastewater during the tunnel construction period according to claim 1, wherein in the step 1, the added flocculating agent is polyacrylamide, the stirring speed of slow stirring is 50-100r/min, and the reaction time after the flocculating agent is added is 2-10 min.
4. The method for treating wastewater during tunnel construction according to claim 1, wherein in the step 1, the solid-liquid separation is one or more of precipitation, centrifugal separation, filtration and air flotation.
5. The method for treating wastewater during tunnel construction according to claim 1, wherein in step 2, the dual-layer Maifanitum composite filler comprises a layer of Maifanitum filler with particle size of 1-3mm and a layer of Maifanitum filler with particle size of 0.5-1mm, and the two layers of Maifanitum fillers are separated by layers through a perforated partition board or a screen with pore size less than 0.5mm, and the filling volume ratio of the two layers of Maifanitum fillers is 1: 10-20.
6. The method for treating wastewater during tunnel construction according to claim 5, wherein in the step 2, the contact time of the wastewater and the Maifanitum filler with the particle size of 1-3mm is 5-8min, and the contact time of the wastewater and the Maifanitum filler with the particle size of 0.5-1mm is 50-160 min.
7. The method for treating wastewater during tunnel construction according to claim 1, wherein in the step 2, medical stone fine powder with a particle size of 0.05mm-0.08mm is added during neutralization flocculation, and the addition amount is 100-500mg/L wastewater; the time for the fourth treated water to carry out neutralization flocculation reaction is 1-5min, and the stirring speed during the reaction is 100-200 r/min.
8. The method for treating wastewater during tunnel construction according to claim 1, wherein the step 2 further comprises measuring pH of the fourth treated water to determine the amount of oxalic acid added so that the pH of the fifth treated water and the final effluent water is 6-9.
9. The method for treating wastewater during tunnel construction according to claim 1, wherein in the step 3, the filtration speed of adsorption filtration is 5-10m/h, the aperture of the screen is less than 0.05mm, the particle size of quartz sand is 1-2mm, and the thickness of the filter layer of the multi-layer filter material is 0.2-1 m.
10. The method for treating wastewater during tunnel construction according to claim 9, wherein in the step 3, the particle size of the activated carbon is 0.2-0.8mm, and the thickness of the filter layer of the multi-layer filter material is 0.2-0.5 m.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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