TWI555708B - System and method for treating simultaneously wastewater containing organic and inorganic pollutants - Google Patents

Description

Wastewater treatment system for removing organic and inorganic pollutants at the same time, and wastewater treatment method

The invention relates to a wastewater treatment system and a wastewater treatment method, and in particular to a wastewater treatment system and a wastewater treatment method capable of simultaneously removing organic pollutants and inorganic pollutants in wastewater.

According to historical and forecast data, from 1990 to 2020, the world's population has grown by about six times, but the water resources on which humans depend for survival have only quadrupled. The lack of water resources and the shortage are the dilemmas that human beings will face together. Solve and overcome. In addition to continuous open source and increased water resources, in addition to saving water in terms of throttling, water recycling is considered an important part. After the wastewater has been properly treated, it can be recycled and reused depending on the target. In the early stage, due to the treatment technology and cost constraints, the main purpose is to remove and reuse the particles and inorganic ions in the water, and it is not common to recycle and reuse the high-concentration organic wastewater. In recent years, membrane bioreactors (MBRs) combined with microbes and membranes have greatly increased the chances of recycling and recycling organic wastewater. However, the organic wastewater itself also contains inorganic ions. Therefore, even after the MBR treatment, the organic waste water remains in the water, so the value of direct water recovery and reuse is not high, even if it is recycled and reused. It is also restricted unless the salt in the water is removed.

In this regard, US Patent Application No. 20100072130 proposes a thin film distillation bioreactor which causes wastewater to flow into a biological reaction tank in which aerobic bacteria are present to decompose organic pollutants in the wastewater by aerobic bacteria, and then distillate. The wastewater is passed through a distillation membrane. Although this U.S. patent mentions that anaerobic bacteria may also be present in the bioreactor, the disclosed thin film distillation bioreactor is only suitable for aerobic bacteria (see, for example, Figures 1, 4, 5, 6, 10, 12). In the examples, there are devices for aerating the biological reaction tank), and it is not suitable for anaerobic bacteria to survive. Therefore, those skilled in the art, after referring to the disclosure of US Patent Application No. 20100072130, can only purify wastewater in a bioreactor containing aerobic bacteria, and cannot purify wastewater in a bioreactor containing anaerobic bacteria. . In addition, since the wastewater in the biological reaction tank needs to be heated to a certain temperature to have a sufficient vapor pressure to pass through the distillation membrane, the temperature of the wastewater in the biological reaction tank is so high that the dissolved oxygen in the wastewater is lowered, and it is disadvantageous. Survival of aerobic bacteria. Furthermore, the wastewater that fails to pass through the distillation membrane will be refluxed into the biological reaction tank so that the wastewater in the biological reaction tank has a cumulative effect of salt concentration, which easily leads to dehydration of the aerobic bacteria osmotic pressure, so the aerobic bacteria The ability to treat wastewater will decrease as operating time increases.

The invention provides a wastewater treatment system, which is suitable for simultaneously purifying a wastewater containing organic pollutants and inorganic pollutants. The wastewater treatment system comprises a medium-high temperature anaerobic tank containing anaerobic bacteria and suitable for being at 30 ° C to 90 ° C. At the temperature, the anaerobic bacteria decompose the organic pollutants in the wastewater, wherein the oxidation and reduction potential of the wastewater in the medium-high temperature anaerobic tank is 0 mV to -600 mV; and a thin film distillation device for separating the high temperature anomalies The wastewater of the oxygen tank allows at least a portion of the wastewater to pass through a membrane of the thin film distillation apparatus in the form of steam to remove inorganic contaminants from the wastewater.

The invention further provides a wastewater treatment method, which is suitable for simultaneously purifying a wastewater containing organic pollutants and inorganic pollutants, comprising flowing the wastewater into a medium-high temperature anaerobic tank containing anaerobic bacteria at 30 ° C to 90 ° C. The organic pollutants in the wastewater are decomposed by anaerobic bacteria at a temperature, wherein the redox potential of the wastewater in the medium-high temperature anaerobic tank is 0 mV to -600 mV; and the wastewater located in the middle and high temperature anaerobic tank flows into the wastewater. In the thin film distillation apparatus, at least a portion of the wastewater is passed through a film of the thin film distillation apparatus in the form of steam to remove inorganic contaminants from the wastewater.

The above described objects, features and advantages of the present invention will become more apparent and understood.

The manner of making and using the embodiments of the present invention will be described in detail below. It should be noted, however, that the present invention provides many inventive concepts that can be applied in various specific forms. The specific embodiments discussed herein are merely illustrative of specific ways of making and using the invention, and are not intended to limit the scope of the invention. Moreover, repeated numbers or labels may be used in different embodiments. These repetitions are merely for the purpose of simplicity and clarity of the invention and are not to be construed as a limitation of the various embodiments and/or structures discussed. Furthermore, when a first element is referred to as being "above", "above" The case of other components. In the drawings, the shapes and thickness of the embodiments may be exaggerated in order to clearly illustrate the features of the invention. Furthermore, in the following, elements constituting or directly related to the elements of the apparatus of the present invention will be specifically described, and elements not shown or described in the drawings may be in various forms well known to those skilled in the art.

The invention provides a wastewater treatment system capable of simultaneously removing organic pollutants and inorganic pollutants in waste water, which is a medium-high temperature anaerobic bacteria to decompose organic pollutants in waste water. Therefore, the invention does not need to additionally install an aeration system, so It can reduce the production cost of the wastewater treatment system.

1 is a schematic view of a wastewater treatment system according to an embodiment of the present invention. In Fig. 1, the flow direction of the wastewater in the wastewater treatment system is represented by an arrow symbol, and in addition, for simplicity of explanation, the pump is omitted in Fig. 1 .

Referring to FIG. 1, the wastewater treatment system 100 of the present embodiment is suitable for simultaneously purifying a wastewater containing organic pollutants and inorganic pollutants. The wastewater treatment system 100 includes a medium temperature anaerobic tank 110 and a thin film distillation unit 120.

The medium-high temperature anaerobic tank 110 is suitable for accommodating waste water and decomposing organic pollutants in the wastewater by an anaerobic bacteria at a temperature of 30 ° C to 90 ° C. The oxidation-reduction potential of the wastewater in the medium-high temperature anaerobic tank is 0 mV to -600. mV is preferably -300 mV to -500 mV.

In addition, since the anaerobic bacteria are microorganisms capable of withstanding high salt concentration, the anaerobic bacteria can maintain good wastewater treatment capacity for a long period of time without being affected by the accumulation of salt concentration in the medium-high temperature anaerobic tank 110. In the present embodiment, the conductivity of the wastewater located in the medium-high temperature anaerobic tank 110 is equal to or greater than 500 μs/cm, and even the conductivity in the tank may be accumulated to more than 3000 μs/cm, in other words, the high temperature annoyance in the present invention. The oxygen tank 110 can perform wastewater treatment at an extremely high salt concentration.

In addition, in the medium-high temperature anaerobic tank 110, there may be methane or hydrogen generated by the organic pollutants in the anaerobic bacteria decomposition wastewater, wherein both methane and hydrogen can be used as fuel. Therefore, the medium-high temperature anaerobic tank 110 can convert organic pollutants in the wastewater into anaerobic bacteria and convert them into fuels of economic value as a source of heating energy for the system.

The thin film distillation apparatus 120 is used for separating the waste water from the medium-high temperature anaerobic tank 110 by passing some or all of the waste water in the form of steam through a film 122 of the thin film distillation apparatus 120 to remove inorganic pollutants in the waste water. . In one embodiment, the film 122 is a hydrophobic material, and the film 122 has a water contact angle of less than 40 degrees. The film 122 has pores (not shown), wherein the pores have an average pore diameter of, for example, 0.01 to 10 μm and a porosity. More than 30%.

In detail, the thin film distillation apparatus 120 has a high temperature film region side 124 and a low temperature film region side 126 separated by a film 122, and the liquid in the high temperature film region side 124 and the liquid in the low temperature film region side 126 There is a temperature difference (vapor pressure difference) between them. After the high temperature wastewater flows into the high temperature film zone side 124, since there is a temperature difference (vapor pressure difference) between the high temperature wastewater and the low temperature wastewater in the low temperature film zone side 126, the steam of the high temperature wastewater passes through the film 122 to reach the low temperature film. In the zone side 126, wastewater having a high inorganic contaminant concentration is left in the high temperature film zone side 124, which can be returned to the intermediate high temperature anaerobic tank 110.

In the present embodiment, the wastewater treatment system 100 can include a heating device 130 for heating the wastewater located in the medium-high temperature anaerobic tank 110, and the heating device 130 can be selected to be anaerobic in the medium-high temperature anaerobic tank 110. The methane or hydrogen produced by the decomposition of the bacteria is an auxiliary fuel. As a result, the need for additional energy for the heating device 130 can be reduced, thereby substantially reducing the energy cost of the wastewater treatment system during operation. In another embodiment, the heating device 130 can include a heating couple 132 disposed in the medium temperature anaerobic tank 110 to heat and maintain the water temperature in the medium temperature anaerobic tank 110.

In the present embodiment, the wastewater treatment system 100 can include a condensing unit 140 and a reflux water storage tank 150, wherein the condensing unit 140 is coupled to the membrane distillation unit 120 and the reflux water storage tank 150, and is condensed in the form of steam through the membrane 122. The water is introduced into the return water storage tank 150. In detail, the condensing device 140 includes a condensing pipe 142 and a heat exchanger 144, wherein the condensing pipe 142 is connected to the thin film distillation device 120 and the return water storage tank 150, and the heat exchanger 144 is connected to the condensing pipe 142 to be used in the condensing pipe 142. The cooling liquid is withdrawn and exchanged for heat to cool it, and then the cooled liquid is injected into the condenser tube 142 to maintain the condenser tube 142 at a low temperature.

A method of treating wastewater using the wastewater treatment system 100 will be described in detail below.

First, the wastewater is placed in an influent water tank 160 connected to the medium-high temperature anaerobic tank 110, and then the wastewater is pumped into the medium-high temperature anaerobic tank 110 by the pump. The heating fluid is used to maintain the wastewater in the medium-high temperature anaerobic tank 110 at 30 ° C to 90 ° C (for example, 55 ± 1 ° C), and the anaerobic bacteria in the medium-high temperature anaerobic tank 110 can decompose organic pollutants in the wastewater. Produce methane or hydrogen. At this time, the methane or hydrogen generated by the decomposition of the anaerobic bacteria can be pumped away from the medium-high temperature anaerobic tank 110 to the heating device 130 to serve as an auxiliary fuel for the heating device 130, thereby reducing the heating device 130 for additional energy. Demand.

Then, the wastewater treated by the medium-high temperature anaerobic tank 110 is pumped to the thin film distillation apparatus 120 for separation. At this time, a part of the wastewater passes through the membrane 122 in the form of steam, and the other part of the wastewater is returned to the middle. In the high temperature anaerobic tank 110.

Thereafter, the water vapor passing through the film 122 is carried away from the surface of the film 122 by condensation of cold water, and is condensed by the condensation pipe 142 to produce water, and flows into the return water storage tank 150, and the reflux water storage tank can be A portion of the water in 150 is pumped into the low temperature membrane zone side 126 to condense the water vapor passing through the membrane 122. The return water storage tank 150 has an overflow port designed to allow the condensed water to flow into the filtrate collection tank 170 connected to the return water storage tank 150.

In addition, in the present embodiment, a chemical cleaning step can be performed on the film 122 to remove inorganic scaling and biofouling generated by filtering the surface of the film 122 for a long time, thereby maintaining the film distillation. The stability of the amount, wherein the chemical cleaning step comprises pickling (for example with sulfuric acid) and medicinal washing (for example with sodium hypochlorite). For example, 1M sulfuric acid can be used for pickling and 1% sodium hypochlorite for drug washing. When pickling with 1 M sulfuric acid, the flow rate is 0.05 m/sec, the frequency is 0.5 hour/day, and 1%. When sodium hypochlorite was used for drug washing, the flow rate was also 0.05 m/sec and the frequency was 0.5 hour/week.

Fig. 2 is a graph showing changes in film flux versus operating time of a thin film distillation apparatus according to an embodiment of the present invention.

Referring to Fig. 2, this embodiment uses a hydrophobic film having a film pore size of 0.22 μm as a film of a thin film distillation apparatus, and maintains a sweep flow rate of 0.05 m/sec. The embodiment is divided into a first stage and a second stage, wherein the first stage is a change of the film flux to the operation time when the film is not subjected to a periodic chemical cleaning step, and the second stage is after the end of the first stage. The change in membrane flux versus operating time for the film during a periodic chemical cleaning step.

In the first stage, the starting flux of the film is 9 LMH (L/m ² /h), and as the operating time increases, the flux of the film slowly decays to 2 LMH, after which a fairly stable operation can be maintained. the amount. When the first stage of the experiment is completed, the chemical cleaning step of the film allows the flux of the film to be restored to 6 LMH, and the operating flux is used as the starting flux for the second stage. Since the second stage of the experiment involves a periodic chemical cleaning step on the film, the film can be maintained at a relatively constant flux.

Figure 3 is a graph showing changes in total organic carbon (TOC) concentration versus operating time for influent wastewater, wastewater in a medium and high temperature anaerobic tank, and wastewater passing through a membrane according to an embodiment of the present invention.

Referring to Figure 3, the TOC concentration of the influent water is between 500 and 1000 mg/L, while the TOC concentration in the medium-high temperature anaerobic tank is lower than the TOC concentration of the influent water, indicating that the TOC is in the medium-high temperature anaerobic tank. There is no cumulative effect of concentration, in other words, anaerobic bacteria in the medium and high temperature anaerobic tank can effectively decompose organic pollutants. The TOC concentration of the distilled filtrate through the membrane is between 1 and 10 mg/L, and the TOC concentration of the distilled filtrate passing through the membrane between the first stage (days 0-40) and the second stage (after day 40) The difference is not large, and most of the TOC concentrations are maintained at about 1 mg/L, which shows that a relatively good treatment water quality can be obtained by the thin film distillation apparatus.

Fig. 4 is a graph showing changes in the conductivity of the influent wastewater, the wastewater in the medium-high temperature anaerobic tank, and the wastewater passing through the membrane according to an embodiment of the present invention.

Referring to Figure 4, the conductivity of the influent wastewater is about 700 μs/cm, while the conductivity of the wastewater in the medium-high temperature anaerobic tank (also representing the concentration of inorganic pollutants in the wastewater) is higher than that of the influent wastewater. This represents a cumulative effect of conductivity in a medium-high temperature anaerobic tank, wherein the conductivity of the wastewater in the medium-high temperature anaerobic tank is maintained substantially at about 3000 μs/cm. The conductivity of the distilled filtrate through the membrane is between 20 μs/cm and 200 μs/cm, and the conductivity is maintained at 100 μs/cm, which means that the thin film distillation apparatus can effectively separate the salts and obtain quite good results. Handle water quality.

In summary, since the wastewater treatment system of the present invention uses a medium-high temperature anaerobic tank to decompose organic pollutants in the wastewater, the present invention can reduce the cost of manufacturing the wastewater treatment system without additional installation of an aeration system. . Furthermore, since there is no need to consider the problem of low oxygen content in the water, the medium-high temperature anaerobic tank can be maintained at a high temperature for a long time without affecting the organic pollutants in the anaerobic decomposition wastewater in the medium-high temperature anaerobic tank. ability. In addition, since anaerobic bacteria are organisms that can withstand high salt concentrations, anaerobic bacteria can maintain a certain wastewater treatment capacity for a long time without being affected by the accumulation of salt concentrations in the medium-high temperature anaerobic tank. Furthermore, the medium-high temperature anaerobic tank can generate economical fuel (methane, hydrogen) by decomposing organic pollutants in the wastewater by anaerobic bacteria, which can be used to heat the wastewater in the medium-high temperature anaerobic tank, thereby reducing The need for additional energy.

The present invention has been disclosed in the above preferred embodiments, and is not intended to limit the scope of the present invention. Any one of ordinary skill in the art can make a few changes without departing from the spirit and scope of the invention. The scope of protection of the present invention is therefore defined by the scope of the appended claims.

100. . . Wastewater treatment system

110. . . Medium and high temperature anaerobic tank

120. . . Thin film distillation unit

122. . . film

124. . . High temperature film side

126. . . Low temperature film zone side

130. . . heating equipment

132. . . Heating coupling

140. . . Condensing device

142. . . Condenser

144. . . Heat exchanger

150. . . Reflux water storage tank

160. . . Inflow sink

170. . . Filtrate collection tank

1 is a schematic view of a wastewater treatment system according to an embodiment of the present invention.

Fig. 2 is a graph showing changes in film flux versus operating time of a thin film distillation apparatus according to an embodiment of the present invention.

Figure 3 is a graph showing changes in total organic carbon (TOC) concentration versus operating time for influent wastewater, wastewater in a medium and high temperature anaerobic tank, and wastewater passing through a membrane according to an embodiment of the present invention.

Fig. 4 is a graph showing changes in the conductivity of the influent wastewater, the wastewater in the medium-high temperature anaerobic tank, and the wastewater passing through the membrane according to an embodiment of the present invention.

100. . . Wastewater treatment system

110. . . Medium and high temperature anaerobic tank

120. . . Thin film distillation unit

122. . . film

124. . . High temperature film side

126. . . Low temperature film zone side

130. . . heating equipment

132. . . Heating coupling

140. . . Condensing device

142. . . Condenser

144. . . Heat exchanger

150. . . Reflux water storage tank

160. . . Inflow sink

170. . . Filtrate collection tank

Claims (19)

A wastewater treatment system suitable for simultaneously purifying a wastewater containing organic pollutants and inorganic pollutants, the wastewater treatment system comprising: a medium-high temperature anaerobic tank containing anaerobic bacteria at a temperature of 30 ° C to 90 ° C Decomposing organic pollutants in the wastewater by anaerobic bacteria, wherein the wastewater in the medium-high temperature anaerobic tank has an oxidation-reduction potential of 0 mV to -600 mV; and a thin film distillation apparatus for separating the high temperature anisotropy from the medium temperature The wastewater of the oxygen tank is such that at least a portion of the wastewater passes through a membrane of the thin film distillation apparatus in the form of steam to remove inorganic contaminants in the wastewater, wherein the wastewater in the medium-high temperature anaerobic tank has a conductivity greater than that of the wastewater Or equal to 200μs/cm. The wastewater treatment system of claim 1, wherein the film is a hydrophobic material and the film has a water contact angle of less than 40 degrees. The wastewater treatment system of claim 1, wherein the film has pores, and each of the pores has a pore diameter of from 0.01 μm to 10 μm. The wastewater treatment system of claim 1, wherein the film has a porosity of more than 30%. The wastewater treatment system of claim 1, further comprising: a heating device for heating the wastewater in the medium-high temperature anaerobic tank. The wastewater treatment system of claim 5, wherein the heating device comprises: a heating coupling disposed in the medium-high temperature anaerobic tank. The wastewater treatment system of claim 5, wherein the medium-high temperature anaerobic tank has methane or hydrogen generated by anaerobic bacteria decomposing organic pollutants in the wastewater, and is suitable as the heating device. Auxiliary fuel. The wastewater treatment system of claim 1, further comprising: a condensing device connected to the thin film distillation device to condense water vapor through the film. A wastewater treatment method suitable for simultaneously purifying a wastewater containing organic pollutants and inorganic pollutants, comprising: flowing the wastewater into a medium-high temperature anaerobic tank containing anaerobic bacteria at a temperature of 30 ° C to 90 ° C The anaerobic bacteria decompose the organic pollutants in the wastewater, wherein the wastewater in the medium-high temperature anaerobic tank has an oxidation-reduction potential of 0 mV~-600 mV, and the wastewater located in the medium-high temperature anaerobic tank The conductivity is greater than or equal to 200 μs/cm; and the wastewater in the medium-high temperature anaerobic tank is flowed into a thin film distillation apparatus, and at least a portion of the wastewater is passed through a film of the thin film distillation apparatus in the form of steam. To remove inorganic contaminants from the wastewater. The wastewater treatment method of claim 9, further comprising: performing a chemical cleaning step on the film, the chemical cleaning step comprising pickling and medicinal washing. The wastewater treatment method according to claim 10, wherein the chemical cleaning step is to clean the film with sulfuric acid and sodium hypochlorite. The wastewater treatment method according to claim 9, wherein The wastewater in the medium-high temperature anaerobic tank has a conductivity greater than or equal to 200 μs/cm. The wastewater treatment method according to claim 9, wherein the film is made of a hydrophobic material, and the water contact angle of the film is less than 40 degrees. The wastewater treatment method according to claim 9, wherein the film has pores, and each of the pores has a pore diameter of 0.01 μm to 10 μm. The wastewater treatment method according to claim 9, wherein the film has a porosity of 30% or more. The wastewater treatment method of claim 9, further comprising: heating the wastewater in the medium-high temperature anaerobic tank with a heating device. The method of treating wastewater according to claim 16, wherein the heating device comprises: a heating coupling disposed in the medium-high temperature anaerobic tank. The wastewater treatment method according to claim 16, wherein the medium-high temperature anaerobic tank has methane or hydrogen generated by the anaerobic bacteria decomposing the organic pollutants in the wastewater, and the heating device is anaerobic. The methane or hydrogen produced by the decomposition of the bacteria is an auxiliary fuel. The method for treating waste water according to claim 9, further comprising: flowing water vapor passing through the film in the form of steam to a condensing device connected to the thin film distillation device, thereby condensing water vapor to form condensation by the condensing device water.