Background technology
Water pollution is the ubiquitous important environmental problem in the whole world, and in Discussion On Measures of Rivers Pollution Treatment process, the improvement of polluted bed mud is main difficult point always.Pollutent is by atmospheric precipitation, rain, discharge of wastewater, soil erosion and the approach such as wash away and enter water body, and sedimentation is enriched in Sediments gradually.By and overlying water between physics, chemistry and biological exchange effect, the pollutent in bed mud can discharge again, becomes the important presence of pollution sources of impact and restriction overlying water matter.
EPA (EPA) proposes " polluted bed mud reparation guide rule " in 2004, has proposed three kinds of main method: dredging, naturally repairing and covering under monitoring.Contaminated bed mud often comprises the complex mixture of poisonous artificial organic and inorganic pollutant.If directly degrade these mixtures, not only cost is large but also efficiency is very limited, if it is recovered naturally, speed is very slow again.In this case, cover to process contaminated bed mud by original position.By covering, bed mud and overlying water are separated, stop the release of pollutants in sediments to overlying water.Meanwhile, covering material is polluted bed mud firmly, prevents that it from suspending or moving, and has adsorption, can reduce to a certain extent the flux of pollutent to overlying water diffusion.In-situ covering method is exactly to cover with layer of material the pollutent that bed mud surface isolates aquatic ecosystem in simple terms.But in the time that covering material is saturated, polluted bed mud there will be again the risk of the mankind and Environmental Health.Remedial measures based on electrochemical techniques is developed, and electrode is likely placed in the pollutent of processing chlorinated solvent and active compound in underground water or bed mud, mixes organic inorganic wastes and heavy metal.Electrode in these cases can be used directly to degradation of contaminant, at electrode isolation pollutent, or collects pollutent for further processing by electrokinetic process; And these processes all require high-voltage or a large amount of electrode, increase cost.Obviously, these methods can't meet user demand at present completely.
Summary of the invention
Goal of the invention: for the deficiencies in the prior art, the object of the present invention is to provide a kind of in-situ remediation method of polluted bed mud, not only can stimulate the contaminant degradation in settling, and create a redox gradient and for contaminant degradation provides electron donor and acceptor, strengthen the degradation efficiency of pollutent in bed mud at bed mud tectum.
Technical scheme: in order to realize foregoing invention object, the technical solution used in the present invention is:
A kind of in-situ remediation method of polluted bed mud: the loess formation that cladding thickness is 10 ~ 15cm on polluted bed mud, loess formation and polluted bed mud interface place establish polarity carbon electrode I, establish polarity carbon electrode II at loess formation and water interface place, polarity carbon electrode I is connected as negative electrode with power cathode, polarity carbon electrode II is connected as anode with positive source, and energising hydrolysis is carried out original position reparation to polluted bed mud.
Described loess density is 2 ~ 3gcm
-3, median size 0.1 ~ 0.2mmol/L.
Described energising hydrolysis, the output voltage of power supply is 3 ~ 4V.
Principle of work: sediment in-situ soverlay technique provided by the invention is to place certain thickness loess at water sludge interface to arrive overlying water layer as barrier isolation Pollutants Diffusion, and settles therein electrode, and when energising hydrolysis, negative electrode produces H
2, the reduction reaction of stimulating organism degraded, anode produces O
2, the oxidizing reaction of stimulating organism degraded; Overcome natural condition and can not provide continuous Redox Condition for the permineralization of pollutent, can not provide enough electron donors and the restricted condition of acceptor for pollutent biological degradation, electron donor and receptor for stimulating microorganism growth are provided when creating a redox gradient rapidly, strengthen the biological degradation of pollutent.
Beneficial effect: compared with prior art, the in-situ remediation method of polluted bed mud of the present invention, not only advantages of simple, in covering material, add electrode, when energising hydrolysis, pollutent in the bed mud of can effectively degrading, in bed mud tectum, create rapidly a redox gradient, electron donor and acceptor are provided simultaneously, stimulate microorganism growth, strengthen the biological degradation of pollutent.
Embodiment
Below in conjunction with specific embodiment, the present invention is further illustrated, and the present invention is not limited only to following examples.
Embodiment 1
As shown in Figure 1, the in-situ remediation method of polluted bed mud, comprises the following steps:
1) place polarity carbon electrode I at muddy water interface perpendicular to contaminant transmission path, polarity carbon electrode I connects power cathode as negative electrode;
2) (loess formation, the density of loess is 2 ~ 3gcm on polarity carbon electrode I, to cover the covering material of 10 ~ 15cm thickness
-3, median size 0.1 ~ 0.2mmol/L);
3) settle another polarity carbon electrode II at loess formation and water interface place perpendicular to contaminant transmission path, polarity carbon electrode II connects positive source as anode;
4) energising hydrolysis, the output voltage of power supply is 3V.
The in-situ remediation method of polluted bed mud is to place certain thickness loess at water sludge interface to arrive overlying water layer as barrier isolation Pollutants Diffusion, and settles therein electrode, and when energising hydrolysis, negative electrode produces H
2, the reduction reaction of stimulating organism degraded, anode produces O
2, the oxidizing reaction of stimulating organism degraded; Overcome natural condition and can not provide continuous Redox Condition for the permineralization of pollutent, can not provide enough electron donors and the restricted condition of acceptor for pollutent biological degradation, electron donor and receptor for stimulating microorganism growth are provided when creating a redox gradient rapidly, strengthen the biological degradation of pollutent.
Embodiment 2
T-cell reactor is as shown in Figure 2 to evaluate carbon electrode as lab setup to create the ability of redox gradient, thereby is reflected in the biodegradability of pollutent under this environment.The settling (taking from the Confucius Temple, the Qinhuaihe River, Nanjing section) of 4cm thickness is placed by this reactor lower floor, and 14 × 7 cm braiding carbon cloths are placed on settling upper strata as polarity carbon electrode I.(density is 2 ~ 3gcm on negative electrode, to place the loess formation of 10cm thickness
-3, median size 0.1 ~ 0.2mmol/L).On loess formation, place 14 × 7 cm braiding carbon cloths as polarity carbon electrode II.In reactor, add and the water of above-mentioned settling with location.Polarity carbon electrode I is connected as negative electrode with power cathode, and polarity carbon electrode II is connected as anode with positive source.
In experiment, compare experiment with three above-mentioned reactors, be labeled as respectively T-cell 1 reactor, T-cell 2 reactors, T-cell 3 reactors.T-cell 1 is connected with two 4 V China instrument 382202 direct supplys with copper cash respectively with the electrode in T-cell 2 reactors.Power supply 1 was to T-cell 1 reactor output voltage 4V continued power 100 days.Power supply 2 is to T-cell 2 reactor output voltage 4V and continue 30 days, then disconnects power supply.T-cell 3 reactors do not connect power supply.Observe above-mentioned three reactors, measure three reactor different steps different depthss (take loess with water layer interface as 0, the degree of depth increases successively) redox potential downwards with Pt microelectrode, thereby reflect the ability of carbon electrode creation redox gradient.Result is as shown in Fig. 3 ~ 5, and in Fig. 3 ~ 5, d represents the degree of depth, and unit is rice.
As Fig. 3, T-cell 1 redox potential variation diagram.Before T-cell 1 reactor output voltage 4V, anode and cathode oxidation reduction potential are poor is 90mV, while continuing output voltage the 98th day, anode and cathode oxidation reduction potential are poor is 700mV, much larger than poor to anode before reactor output voltage and cathode oxidation reduction potential.
As Fig. 4, T-cell 2 redox potential variation diagrams.Before T-cell 2 reactor output voltage 4V, anode and cathode oxidation reduction potential are poor is 80mV, while continuing output voltage the 28th day, anode and cathode oxidation reduction potential are poor is 700mV, much larger than poor to anode before reactor output voltage and cathode oxidation reduction potential.Power supply disconnection rear oxidation reduction potential is poor to be reduced gradually.
As Fig. 5, T-cell 3 redox potential variation diagrams.In T-cell 3 reactors initial anode poor with cathode oxidation reduction potential be 65mV, the 98th day time, anode and cathode oxidation reduction potential are poor is 5mV, the little redox potential of maintenance variation is poor substantially.
Draw thus, in reactor owing to adding electrode output voltage creating rapidly a redox gradient, having overcome natural condition can not provide for the permineralization of pollutent the restriction of continuous Redox Condition, thereby strengthens the ability of microbiological oxidation organic pollutant.
Embodiment 3
As shown in Figure 6, be laboratory test reactor, it contains two glass chambers, is connected with cationic exchange membrane, settles respectively the carbon cloth of 12.6 × 6.25cm as electrode in glass chamber; Two electrodes are by diameter 0.64cm, and the graphite rod of length 15.2cm is connected with an E3620A DC power supply; Each chamber has 60ml headspace and 250ml buffered soln, and buffered soln contains 20mmol/L NaHCO
3with 20mmol/L NaCl, and regulate pH to 6.5 with the NaOH of 5% concentration, match with the intensity of bed mud pore water.This unit simulation conventional water environment, be used for test voltage, primary pollutant concentration and the impact of natural organic matter concentration on degradation of contaminant, thereby for the tectal design of original position that contains electrode provides reference data, make best design.
Oil of mirbane is pollutent more common in general waters.Take oil of mirbane as pollutent, study respectively applied voltage, the impact of the existence of primary pollutant concentration and natural organic matter on contaminant degradation.In a chamber, add oil of mirbane therein, in reduction reaction, be connected to power cathode as negative electrode, then in oxidizing reaction, be switched to anodal as anode.In this reactor, oil of mirbane is aniline by theory in cathodic reduction, and intermediate product is nitrosobenzene, and aniline is removed at anode subsequently.
As Fig. 7, the impact of test applied voltage p-nitrophenyl rate of reduction.When voltage 2V during to 3.5V the rate of reduction of oil of mirbane be increased to 1.6 h 1 from 0.3 h 1, the rate of reduction of nitrosobenzene is from 0.04 h
1be increased to 0.64 h
1; Voltage is during higher than 3.5V, and the rate of reduction of oil of mirbane and nitrosobenzene does not continue to increase with voltage; When voltage is less than 2V, instead would not occur.
As Fig. 8, test initial nitro phenenyl concentration p-nitrophenyl rate of reduction impact.If initial nitro phenenyl concentration is reduced to 5 μ M from 100 μ M, nitrobenzene reduction speed is from 0.88 h
1be increased to 7.9 h
1, rate of reduction 0.36 h of nitrosobenzene
1be increased to 1.7 h
1.
As Fig. 9, test the natural organic impact that has p-nitrophenyl rate of reduction.Test with humic acid solution (containing 14.4 mg/L DOC).In the time there is no natural organic matter, nitrobenzene reduction rate constant is 2.2 h
1.While adding humic acid solution, nitrobenzene reduction rate constant is 0.8 h
1.And nitrosobenzene rate of reduction constant is all at 0.4 h
1left and right.
Sediment in-situ soverlay technique provided by the invention is to arrive overlying water layer at the loess of sediment water interface placement 10 ~ 15cm thickness as barrier isolation Pollutants Diffusion; Because natural condition can not provide continuous Redox Condition for the permineralization of pollutent, can not provide enough electron donor and acceptors for pollutent biological degradation.The present invention settles electrode in Upper loess covering, and electron donor and receptor for stimulating microorganism growth are provided when creating rapidly a redox gradient, strengthens the biological degradation of pollutent.Reach a conclusion from above experiment, when voltage 2V during to 3.5V oil of mirbane and nitrosobenzene rate of reduction constant all increase with the increase of applied voltage, when voltage stops increasing during higher than 3.5V, therefore preferred voltage is 3 ~ 4V.In the time that initial nitro phenenyl concentration is reduced to 5 μ M from 100 μ M, nitrobenzene reduction rate constant becomes original 9 times, and nitrosobenzene rate of reduction constant becomes original 5 times.The existence of natural organic matter reduces nitrobenzene reduction speed, and nitrosobenzene rate of reduction is substantially constant.