Patent Grant
10800686
The present invention relates to an apparatus and a method for removing nitrogen and phosphorus in sewage by using sponge iron and activated sludge.
In recent years, due to continuous development of sewage treatment fillers, carrier—bound microbiological immobilization method has become popular. It is a method to keep free cells or enzymes active and reusable by positioning the same within a defined spatial region using chemical or physical means, which has an advantage of high biological density and rapid response. In particular, organic porous carriers, which is represented by polyurethane foam, provide an aerobic and anoxic microenvironment required for the growth of nitrifying bacteria due to its unique spatial structure, thereby providing reactors with the possibility for simultaneous nitrification and denitrification. The carriers, though greatly increase the rate of denitrification in the aerobic reactor, have little effect on phosphorus removal. Studies have demonstrated that zero-valent iron materials can improve the treatment effect of the reactor to a certain extent through the improvement of microbial activity and chemical flocculation, especially iron will react with phosphorus to precipitate such that the phosphorus removal effect is enhanced.
Sponge iron has characteristics of large specific surface area and high specific surface energy due to its loose spongy structure, meanwhile it also has properties as strong electrochemical enrichment, redox, physical adsorption, and flocculation precipitation. Sponge iron as an immobilized biological carrier filler has the following advantages: 1) provides sufficient space for microbial enrichment and growth, and provides a good “microenvironment” for the synergistic symbiosis of various aerobic, facultative, and anaerobic microorganisms in biochemical reactors; 2) can form a large number of primary batteries due to the special chemical composition, the nascent state Fe2+ produced by the electrode reaction, and the further oxidized Fe3+ and their hydrates, under the action of precipitation, flocculation, adsorption and sweeping, etc. may greatly reduce the concentration of nitrogen and phosphorus in the sewage; 3) has the effect of biological iron, which can enhance the purification function of activated sludge. However, in practical engineering applications, sponge iron has the problems of easy sinking, poor fixation, and small contact with the sewage, and in particular, it will be difficult to directly feed into a biochemical pool owing to its hardening.
How to improve the efficiency and effectiveness of nitrogen and phosphorus removal from sewage by using sponge iron has become a hotspot in research.
With regard to the problems existing in the prior art, the present inventors have surprisingly found that the nitrogen and phosphorus removal efficiency can be improved by modifying sponge iron and inoculating activated sludge as compared with the conventional sewage treatment using the sponge iron.
An object of the present invention is to provide a method for removing nitrogen and phosphorus from sewage, comprising steps of sponge iron modification, preparation of a composite filler, inoculation and domestication of sludge, and sewage treatment.
In the above solution,
According to an aspect of the present invention, the method for removing nitrogen and phosphorus from sewage may comprise the following steps:
1) washing the sponge iron with the dilute acid solution, and then heating under reflux with the dilute acid solution, by controlling the temperature not exceed 60° C., after heating is stopped, rinsing the solution with a deionized water to neutral; placing the solution in the copper sulfate solution to react and controlling the temperature of the solution to 32-36° C., removing the remaining solution by filtration and washing the solid portion with pure water and drying to obtain the modified sponge iron solid;
According to an aspect of the present invention, the method for preparing the paulownia coarse grain is: washing branches of the natural Paulownia, cutting into segments of 3 to 20 cm in length, uniformly spraying on the surface with 3% in weight concentration of sodium bicarbonate solution, placing in a steam oven with steam for 2-5 h, removing and cooling to room temperature, drying, crushing with a pulverizer to obtain a coarse grain in a diameter of 1-3 mm.
According to an aspect of the present invention, the activated sludge is prepared by mixing the remaining fresh sludge from sewage treatment plant and granular sludge from anammox and anaerobic granular sludge at a volume ratio of 2:1 so that the concentration of the granular sludge is about 3 to 5 g/L, the mixed activated sludge contains both aerobic bacteria and anaerobic bacteria.
Further, the activated sludge is also inoculated with iron bacteria, preferably, the percentage of the iron bacteria in the total weight of the activated sludge is 0.03-0.1 wt %, which can realize the oxidation of iron, by the biological oxidation of FeP→Fe2+Fe3+, a complementary effect can be achieved by the composite filler made therefrom with sponge iron in a same reactor, especially the phosphorus removal efficiency is improved.
Further, the replaced composite filler may be subjected to recycle treatment: the composite filler that is replaced after 5 to 8 cycles is subject to microwave radiation treatment, and the microwave power is 1100-1300 W, and the processing time is 3-10 min, then is washed with pure water to neutral, dried, mixed with equal weight of polyethylene glycol powder and 0.2-3% of ethylene glycol, extruded and pelletized with a twin-screw extruder to obtain pellets, the pellets and the microwave-treated composite filler are mixed, then 0.1 to 0.5% of a chemical foaming agent is added, mixed uniformly, and extruded using multiple single-screw extruders in series to obtain a regenerated composite filler, which can further be used for 2-4 cycles.
Another object of the present invention is to provide an apparatus for removing nitrogen and phosphorus in sewage by using sponge iron and activated sludge to realize rapid and efficient nitrogen and phosphorus removal.
In particular, an apparatus for removing nitrogen and phosphorus from sewage using sponge iron and activated sludge, comprising a raw tank for accommodating sewage, a pH adjusting tank connected to the raw tank to adjust the pH of the sewage to neutral and is provided at bottom with a first vent valve for discharging sewage and sludge, a temperature adjustment device inside the pH adjusting tank to adjust the temperature of the sewage to 28-32° C., a primary SBR reactor connected to the pH adjusting tank for accommodating the composite filler prepared from the sponge iron, acclimating the activated sludge and conducting sewage treatment, an intermediate tank connected to the primary SBR reactor and is provided at bottom with a second vent valve for emptying the sewage, a secondary SBR reactor connected to the intermediate tank and the pH adjusting tank, respectively, for accommodating the composite filler prepared from the sponge iron, acclimating the activated sludge and conducting sewage treatment, and a discharge tank connected to the secondary SBR reactor and is provided at bottom with a third vent valve for discharging sewage and sludge.
In the above solution, the primary SBR reactor may comprise: a first aeration device located at a lower part, which is supplied by an external first air pump, wherein a first gas flow control valve is provided at a pipeline between the first aeration device and the first air pump, a first support plate above the first aeration device, a first filler stents mounted between the first support plate and the top of the primary SBR reactor for accommodating the composite filler prepared from sponge iron, a first agitator between the first aeration device and the first support plate, the first agitator being driven by a first drive motor located outside the primary SBR reactor, a dissolved oxygen concentration measuring device for determining the dissolved oxygen concentration in the primary SBR reactor, and a first drain valve located at an upper part for discharging the sewage in the primary SBR reactor to the intermediate tank.
Particularly suitably, the volume of the first filler stents accounts for ⅗ to ⅘ of the total volume of the primary SBR reactor.
In the above solution, the secondary SBR reactor may comprise: a second aeration device located at a lower part, which is supplied by an external second air pump, wherein a second gas flow control valve is provided at a pipeline between the second aeration device and the second air pump, a second support plate above the second aeration device, a second filler stents mounted between the second support plate and the top of the secondary SBR reactor for accommodating the composite filler prepared from sponge iron, a second agitator between the second aeration device and the second support plate, the second agitator being driven by a second drive motor located outside the secondary SBR reactor, a dissolved oxygen concentration measuring device for determining the dissolved oxygen concentration in the secondary SBR reactor, and a second drain valve located at an upper part for discharging the sewage in the secondary SBR reactor to the discharge tank.
Particularly suitably, the volume of the second filler stents accounts for ⅗ to ⅘ of the total volume of the secondary SBR reactor.
In the abovementioned solution, the apparatus may further comprise a multi-stage filtration adsorption column to purify water from the discharge tank, and discharge the purified water from an outlet of the multi-stage filtration adsorption column.
In one or more of the above aspects, a first to fourth inlet pumps are provided between the pH adjustment tank and the primary SBR reactor and the secondary SBR reactor, between the intermediate tank and the secondary SBR reactor, and between the discharge tank and the multi-stage filtration adsorption column, for pumping sewage between the respective containers, the first inlet water pump, the second inlet water pump, the third inlet water pump, the first gas flow control valve, and the second gas flow control valves are all electrically connected to the PLC automation controller for control operation.
According to an aspect of the present invention, the method of removing nitrogen and phosphorus from sewage according to the present invention may be performed in the apparatus according to the present invention.
Beneficial Effects of the Present Invention
In the present invention, sponge iron is made into a suitable composite filler and fed into a reactor, inoculates activated sludge, and used for two-phase treatment of sewage by SBR reactors, aerobic nitrification and anaerobic denitrification are alternatively conducted by combined action of sponge iron, activated sludge and iron bacteria, and by the control of the concentration of dissolved oxygen in the SBR reactors, such that an effect of simultaneous denitrification and dephosphorization is achieved in one reactor, the present method for sewage treatment has excellent effect on nitrogen and phosphorus removal.
Materials and reagents used in the examples are all conventionally used in the art or commercially available unless otherwise specified.
As shown in
A general urban sewage is selected as the raw water, the sampling volume is 100 L, the sampling is repeated twice. The main water quality indicators are determined by a water quality analyzer as: CODCr=360-400 mg/L, BOD5=120-260 mg/L, SS=120-250 mg/L, ammonia nitrogen=25-50 mg/L, TN=13-60 mg/L, TP=3-7 mg/L.
The nitrogen and phosphorus removal from sewage is conducted using the present apparatus, comprising:
the main water quality indicators of the effluent are determined and the results are: CODCr=10-20 mg/L, BOD5=1-2 mg/L, SS=0 mg/L, Ammonia nitrogen=0.5-4 mg/L, TN=1-7 mg/L, TP<0.3 mg/L, removal efficiency: CODCr≥96%, BOD5≥97%, SS=100%, TN≥87%, TP≥92%.
Example 2 is substantially the same as Example 1, except that the activated sludge is further inoculated with iron bacteria, and the iron bacteria account for 0.03 wt % of the total weight of the activated sludge. The results are: CODCr=10-20 mg/L, BOD5=1-2 mg/L, SS=0 mg/L, TN=1-5.8 mg/L, TP<0.26 mg/L, removal efficiency: CODCr≥96%, BOD5≥97%, SS=100%, TN≥90.6%, TP≥95%.
Conclusion: After the inoculation of iron bacteria in activated sludge, the removal of phosphorus is significantly enhanced.
The treated water of Example 1 is further passed through a multi-stage filtration adsorption column 5 (as shown in
Conclusion: The removal rate of nitrogen and phosphorus is further increased by multi-stage filtration and adsorption column treatment.
The replaced composite filler in Example 1 is subjected to microwave irradiation for 7 minutes and the microwave power is 1200 W. Then it is washed with pure water to neutral, dried, and mixed with equal weight of polyethylene glycol powder and 1.6% of ethylene glycol, extruded and pelletized with a twin-screw extruder to obtain pellets. The pellets are mixed with microwave-treated composite fillers and 0.3% of a chemical foaming agent is added and mixed uniformly, extruded with a plurality of multiple single-screw extruders connected in series to obtain a regenerated composite filler.
The regenerated composite filler is loaded into the primary SBR reactor 3, and the processing conditions are the same as those in Example 1. After 3 cycles, the results are: CODCr=15-40 mg/L, BOD5=2-11 mg/L, SS=0 mg/L. Ammonia nitrogen=5-24 mg/L, TN=1-12 mg/L, TP<0.7 mg/L, removal efficiency: CODCr≥92.7%, BOD5≥96%, SS=100%, TN≥82.2%, TP≥86%.
Conclusion: the replaced composite fillers can be reused for sewage treatment through recycling. Although the processing capacity has been reduced, the overall effect is good.
the effect of the volume of different filler scaffolds on the treatment effect was determined using the method of Example 1:
The results are: CODCr=12-32 mg/L, BOD5=1-2.2 mg/L, SS=0 mg/L, TN=1-10 mg/L, TP<0.38 mg/L, removal efficiency: CODCr≥92%, BOD5≥95.6%, SS=100%, TN≥86.8%, TP≥90.9%.
The results are: CODCr=10-20 mg/L, BOD5=1-2 mg/L, SS=0 mg/L, TN=1-5 mg/L, TP<0.28 mg/L, removal efficiency: CODCr≥95%, BOD5≥97%, SS=100%, TN≥91.6%, TP≥92.8%.
The results are: CODCr=12-30 mg/L, BOD5=1-2.3 mg/L, SS=0 mg/L, TN=1-10 mg/L, TP<0.35 mg/L, removal efficiency: CODCr≥93%, BOD5≥96.8%, SS=100%, TN≥85.3%, TP≥91.5%.
The results are: CODCr=20-40 mg/L, BOD5=1-4 mg/L, SS=0 mg/L, TN=1-20 mg/L, TP<0.85 mg/L, removal efficiency: CODCr≥92.1%. BOD5≥95.2%, SS=100%, TN≥71.2%, TP≥83%.
Conclusion: When the volume of the filler stents is ⅗-⅘ and ⅖-⅘ respectively, the sewage treatment capacity is relatively strong, and is strongest at 7/10, as volume becomes larger or smaller, the capacity for sewage removal of the device has declined (data not shown).
The effect of different dissolved oxygen concentrations on the treatment effect is measured using the method of Example 1.
The early-stage dissolved oxygen concentration (DO) is 2.9 mg/L, and the late-stage dissolved oxygen concentration (DO) is 0.04 mg/L.
The results are: CODCr=10-20 mg/L, BOD5=1-2 mg/L, SS=0 mg/L, ammonia nitrogen=0.5-4 mg/L, TN=1-5.3 mg/L, TP<0.2 mg/L, removal efficiency: CODCr≥96%, BOD5≥97%, SS=100%, TN≥89.2%, TP≥92.5%.
The early-stage dissolved oxygen concentration (DO) is 3.5 mg/L, and the late-stage dissolved oxygen concentration (DO) is 0.08 mg/L.
The results are: CODCr=10-26 mg/L, BOD5=1-2 mg/L, SS=0 mg/L, ammonia nitrogen=0.5-6 mg/L, TN=1-8 mg/L, TP<0.4 mg/L, removal efficiency: CODCr≥96%, BOD5≥97%, SS=100%, TN≥87%, TP≥92%.
Comparative Example 1: the early-stage dissolved oxygen concentration (DO) is 1.5 mg/L, and the late-stage dissolved oxygen concentration (DO) is 0.0005 mg/L.
The results are: CODCr=18-30 mg/L, BOD5=2-20 mg/L, SS=0 mg/L, ammonia nitrogen=5-24 mg/L, TN=2-16 g/L, TP<1.5 mg/L, removal efficiency: CODCr≥93.6%, BOD5≥94.2%, SS=100%, TN≥75.3%, TP≥70%.
Comparative Example 2: the early-stage dissolved oxygen concentration (DO) is 4 mg/L, and the late-stage dissolved oxygen concentration (DO) is 0.1 mg/L.
The results are: CODCr=18-40 mg/L, BOD5=2-28 mg/L, SS=0 mg/L, ammonia nitrogen=5-24 mg/L, TN=3-20 mg/L, TP<2.2 mg/L, removal efficiency: CODCr≥92.3%, BOD5≥92.1%, SS=100%, TN≥68.5%, TP≥56%.
Conclusion: when the early-stage dissolved oxygen concentration is in the range of 2.3-3.5 mg/L, and the late-stage dissolved oxygen concentration is in the range of 0.01 mg/L≤DO<0.08 mg/L, the capacity of sewage treatment is relatively good, especially when the early-stage dissolved oxygen concentration (DO) is 2.9 mg/L, and the late-stage dissolved oxygen concentration (DO) is 0.04 mg/L, the capacity of sewage treatment is the best. When the early-stage and late-stage dissolved oxygen concentration are not within the above range, the sewage treatment capacity was relatively low.
Compared with Example 1, the composition and proportions of modified sponge iron and other components are different, and the resulting composite filler components are different, as shown in Table 1:
The results of Comparative Example 1 are: CODCr=10-20 mg/L, BOD5=1-2 mg/L, SS=0 mg/L, TN=1-7.8 mg/L, TP<0.38 mg/L, removal efficiency: CODCr≥96%, BOD5≥97%, SS=100%, TN≥83.5%, TP≥89.4%.
The results of Comparative Example 2 are: CODCr=10-20 mg/L, BOD5=1-2 mg/L, SS=0 mg/L, TN=1-6 mg/L, TP<0.4 mg/L, removal efficiency: CODCr≥96%, BOD5≥97%, SS=100%, TN≥84.6%, TP≥88.2%.
Conclusion: The sponge iron and the final composite filler prepared by the method and the component proportions of Example 1 has the best sewage treatment capacity.
The effect of different sewage temperature on the treatment effect is determined using the method of Example 1, as shown in Table 2:
Conclusion: When the sewage temperature is 28-32° C., the treatment effect is excellent, especially at 30° C., the sewage treatment effect is best, when the sewage temperature is lower than 28° C. or higher than 32° C., the sewage treatment effect decreased significantly.
The sewage treatment process and system provided by the present invention have been described in detail above. The specific embodiments are used in this specification to describe the principle and implementation manners of the present invention. For those skilled in the art, the specific implementation manner and application scope may change during implementation based on the ideas according to the present invention. Therefore, what is described in the present specification should not be construed as limiting the present invention.
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| Number | Date | Country | |
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| 20200109073 A1 | Apr 2020 | US |
