CN105541057A - Resource utilization method for pig farm biogas slurry - Google Patents

Abstract

The invention relates to a method for resource utilization of pig farm biogas slurry, that is, the fermented biogas slurry of pig farms is sequentially passed through multi-stage aeration and filtration, inoculated and cultivated with photosynthetic bacteria, inoculated with cladocera filter-feeding photosynthetic bacteria and collected cladocera, The filtrate is inoculated with single-cell algae and cultured, inoculated with cladocera filter-feeding single-cell algae and collected cladocera, and the treated water reaches the standard for reuse or discharge. During the treatment process, photosynthetic bacteria are first used to degrade the organic matter in the biogas slurry and generate bacteria. , and then use microalgae to absorb nutrients such as nitrogen and phosphorus in the water body and generate algae, and use cladocera to filter-feed bacteria and algae in the water body non-selectively. The pig farm biogas slurry resource utilization method of the present invention can use the photosynthetic bacteria, unicellular algae and cladocera generated in the biogas slurry treatment process for aquaculture and bait, and realize resource utilization of the pollutants in the biogas slurry by means of the food chain, It has the characteristics of low investment, low energy consumption, and can produce obvious economic and ecological benefits.

Description

A method for resource utilization of pig farm biogas slurry

technical field

The invention relates to the technical field of pig farm biogas slurry treatment, in particular to a method for resource utilization of pig farm biogas slurry.

Background technique

With the growth of population, the improvement of people's living standards and the rapid development of social economy, the human demand for animal protein is also gradually increasing. The key to solving the shortage of human animal protein depends on breeding, and the development of livestock and aquaculture is an important measure to solve the shortage of animal protein. The waste gas, waste liquid and waste residue produced in the process of large-scale livestock and poultry breeding often cause great pressure on the surrounding ecological environment protection. Breeding pollution has become the main source of agricultural and rural environmental pollution. Breeding sewage and liquid excrement are the difficulties in the harmless treatment of pollutants in intensive livestock and poultry farms. The main pollutants are organic matter, nitrogen and phosphorus. At present, the sewage of large-scale livestock and poultry farms is usually treated by anaerobic fermentation in biogas tanks (Technical Specifications for Pollution Control Engineering of Livestock and Poultry Breeding Industry), but the huge amount of biogas slurry still contains high concentrations of nutrients such as nitrogen and phosphorus. Taking pig farms as an example, the concentration of pollutants in the biogas slurry is still high after the aquaculture sewage is treated by anaerobic fermentation in the biogas tank, and the concentrations of BOD ₅ , ammonia nitrogen and total phosphorus are as high as 389mg/L, 578.5mg/L and 32.9 mg/L, there is still a large distance from the national livestock and poultry breeding pollutant discharge standard (DB33/593-2005; GB/T18596-2001) (BOD ₅ , total nitrogen and total The maximum allowable daily average discharge concentration of phosphorus is 150mg/L, 80mg/L and 8mg/L respectively). Directly discharging the generated biogas slurry to the water body will inevitably lead to serious eutrophication of the natural water body. Therefore, biogas slurry still needs secondary treatment. There are two conventional treatment modes for biogas slurry in livestock and poultry farms, one is the "standard discharge" mode and the other is the "comprehensive utilization" mode ("Large-scale Livestock and Poultry Farm Biogas Engineering Design Regulations" (NY/T1168)) . Under the standard discharge mode, after anaerobic digestion treatment, livestock and poultry wastewater must undergo appropriate aerobic treatment or natural treatment, etc., to meet the specified environmental protection standards for discharge or reuse. The project cost and operation cost of this mode are relatively high, and it is a non-resource utilization mode. The "comprehensive utilization" mode is to discharge biogas slurry into the farmland and rely on the natural absorption of crops, which is a low-efficiency resource utilization mode. With the development of social economy, the disadvantages of this treatment method are becoming more and more obvious: first, the treatment effect is difficult to guarantee due to the influence of crop growing season; second, the adjustment of agricultural industrial structure and the acceleration of urbanization development make the arable land for digesting biogas slurry insufficient , Therefore, it is particularly necessary to adopt other more efficient ways to carry out advanced treatment of biogas slurry. How to purify biogas slurry has increasingly become a restrictive factor for the sustainable production of large-scale livestock and poultry farms.

Photosynthetic bacteria (Photosynthetic Bacteria, referred to as PSB) are the earliest prokaryotic organisms that appeared on the earth, are ubiquitous in nature, and have a primitive light energy synthesis system. , Microbes that can use organic matter, sulfide, ammonia, etc. in nature as hydrogen donors and carbon sources for photosynthesis under anaerobic light or aerobic dark conditions, play an important role in the purification process of natural substances, especially for degradation The organic matter in the water body has an obvious effect and plays a role in purifying the water quality.

As a class of low-level photoautotrophic organisms, microalgae are rich in species. Microalgal cells can use light energy as energy to absorb nutrients such as nitrate nitrogen, ammonia nitrogen, and phosphate from water to synthesize cell components. Existing experimental studies have shown that different microalgae have different tolerance, absorption and utilization capabilities to different forms of nitrogen, phosphorus and other nutrients in water. In terms of the practice of using microalgae to purify sewage, in 1957, Oswald et al. first used microalgae as a biological system to replace activated sludge in sewage treatment, laying the foundation for algae sewage biological treatment technology. Since then, people have paid more and more attention to the application of the combination of bacteria and algae, and the oxidation pond technology based on the principle of algae-bacteria symbiotic self-purification in artificial model water has been widely used and developed. In recent years, studies on the coupling of livestock and poultry sewage purification to the production of high value-added products from microalgae have also been reported, mainly focusing on the field of microalgae biodiesel production using livestock and poultry sewage. Hu Hongying et al. (2009) discussed the coupling technology of deep water purification and high-value biomass production based on microalgae cell culture. Sydney et al. (2010) pioneered the coupling of microalgae wastewater treatment and microalgae biodiesel production. Hu Hongying and Li Xin (2010) analyzed the key technology and potential analysis of using sewage resources to produce microalgae biodiesel.

Cladocera, belonging to the phylum Arthropoda, Crustacea, Branchopod, and small crustaceans of Cladocera, are widely distributed in fresh water, sea water and inland brackish water, and are high-quality natural bait for aquatic animals. Some of them have Strong pollution resistance, non-selective filter-feeding of organic detritus, algae cells and bacteria in the water body, so as to transform the micro nutrients that are difficult to harvest in the water body into small particles that are easy to harvest

To sum up, the development of recyclable, efficient and low-cost sewage treatment technology is an important measure for the sustainable development of large-scale livestock and poultry farming. The comprehensive utilization of livestock and poultry breeding waste and turning waste into treasure is the fundamental way to reduce the random discharge of livestock and poultry breeding waste and fundamentally solve the problem of livestock and poultry breeding pollution prevention and control.

Contents of the invention

The purpose of the present invention is to provide a method for resource utilization of pig farm biogas slurry in view of the deficiencies in the prior art, but there is no report about this method for resource utilization of pig farm biogas slurry.

For realizing above-mentioned object, the technical scheme that the present invention takes is:

A method for resource utilization of pig farm biogas slurry, characterized in that the fermented biogas slurry flowing out of the pig farm biogas digester is sequentially passed through multi-stage aeration and filtration, inoculated and cultivated with photosynthetic bacteria, inoculated with cladocera filter-feeding photosynthetic bacteria and Collect cladocera, inoculate the filtrate with unicellular algae and cultivate them, inoculate cladocera filter-feeding unicellular algae and collect cladocera, and discharge or reuse the treated water that meets the standard. During the treatment process, photosynthetic bacteria are used to degrade the biogas slurry Then use microalgae to absorb nutrients such as nitrogen and phosphorus in the biogas slurry and generate algal cells, and then use organic debris, photosynthetic bacteria and single cells formed during the non-selective filter feeding process of Cladocera Algae, Cladocera, photosynthetic bacteria, and single-cell algae produced can be used in aquaculture or bait, so as to realize the resource utilization of pollutants in biogas slurry.

Furthermore, the fermented biogas liquor flowing out of the pig farm biogas digester is firstly filtered through multi-stage aeration, and the specifications of the multi-stage aeration and filtration stainless steel screens used are 200 mesh, 300 mesh, 400 mesh and 500 mesh in sequence. It is inclined at a certain angle, and nano-aeration tubes are installed at the bottom of the screen to blow off part of the ammonia nitrogen in the biogas slurry under the action of aeration, while preventing the mesh of the screen from being blocked.

Further, photosynthetic bacteria are inoculated in the biogas slurry filtered through multistage aeration to degrade and absorb organic matter. The species of photosynthetic bacteria are Rhodopseudomonas, Rhodospirillum and Rhodobacter. The ratio of the initial inoculum of bacteria to the biogas slurry filtered by multi-stage aeration is 3:7-5:5. The inflow and outflow speeds of photosynthetic bacteria liquid are continuously cultivated, and the inflow and outflow speeds are adjusted according to the growth of photosynthetic bacteria.

Further, part of the cultured photosynthetic bacteria can be directly harvested for aquaculture production according to needs, and the other part of the outflowing photosynthetic bacteria liquid enters the square culture tank, inoculates cladocera, and utilizes cladocera to filter-feed them non-selectively. The organic detritus and photosynthetic bacteria in the water body can remove the organic and inorganic particles in the water body and improve the transparency of the water body. The species of Cladocera inoculated are Moinaaffinis of the genus Pyrophylla and Daphniamagna of the genus and the weevil flea Bosminalongirostris.

Further, the cultivated Cladocera can be enriched through a filter harvesting device, and the enriched Cladocera can be used as live bait for aquatic animal seedlings or ornamental fish, and can also be recycled for filter-feeding single-cell algae.

Further, through biogas slurry fed by Cladocera once, unicellular algae are inoculated to absorb nutrients such as nitrogen and phosphorus in the water body. The algae of the genus Chlorococcum and the genus Scenedesmus, the ratio of the initial inoculum of single cells to the biogas slurry that has been filtered by Cladocera is 1:1~5, in a transparent plexiglass column or a columnar flexible plastic film bag After 5-10 days of aerated culture, maintain a certain biogas slurry inflow and single-cell algae liquid outflow speed to implement continuous culture, and the inflow and outflow speed is adjusted according to the growth of single cells and the content of nitrogen and phosphorus in the water.

Further, part of the cultivated algae liquid can be directly harvested for aquaculture production according to needs, and the other part of the outflowed algae liquid enters the square culture tank and is inoculated with cladocera, utilizing the non-selective filter-feeding characteristics of cladocera. The organic detritus and unicellular algae among them are filtered for the second time, and the water body is further purified. The species of Cladocera inoculated are Moinaaffinis of the genus Pleia, Daphniamagna of the genus Daphniamagna, and the genus Elephantis Elephant flea Bosminalongirostris.

Furthermore, the biogas slurry that has undergone the secondary filtering of Cladocera can be treated and discharged as up-to-standard water after being tested to meet the sewage discharge standards for livestock and poultry farming, or reused as manure flushing water for pig houses. If the test does not meet the discharge standards, then Do repeated processing.

The present invention has the advantage that:

1. The pig farm biogas slurry resource utilization method of the present invention can use the photosynthetic bacteria, unicellular algae and cladocera generated in the biogas slurry treatment process for aquaculture and bait, and realize resource utilization of the pollutants in the biogas slurry by means of the food chain Utilization has the characteristics of low investment, low energy consumption, and can produce obvious economic and ecological benefits;

2. Traditional wastewater treatment projects can only reduce the discharge volume and intensity of pollutants, and usually produce few products, which can only produce environmental, ecological and social benefits, and are difficult to produce economic benefits. This mode of only investing but not producing results in enterprises being inactive in environmental protection investment, and the present invention couples sewage treatment with live bait production, not only can realize effective treatment of sewage, but also can reduce the cost of live bait production and realize environmental sustainability and resource recycling, in line with the national trend of developing ecological agriculture, green agriculture and circular agriculture;

3. The sewage from livestock and poultry breeding is not only a serious source of pollution, but also a valuable resource. However, the present invention introduces photosynthetic bacteria, microalgae and Cladocera into the traditional livestock and poultry breeding sewage treatment process, and couples the pig farm biogas slurry purification and live bait production through the photosynthetic bacteria-microalgae-Cladocera food chain. Photosynthetic bacteria and microalgae are cultivated with high-concentration nitrogen, phosphorus, organic matter and other nutrients in the liquid, and the cultured photosynthetic bacteria and microalgae are filtered through cladocerae to produce live bait for animal breeding and production, so as to achieve environmental protection and resource efficiency Recycling ensures the sustainable development of production and ecology.

Description of drawings

Accompanying drawing 1 is a schematic flow chart of a method for resource utilization of swine farm biogas slurry according to the present invention.

detailed description

Example 1

In a large-scale standardized pig breeding enterprise in Chongming, Shanghai, the resource utilization and purification treatment of pig farm biogas slurry based on photosynthetic bacteria-microalgae-cladocera was carried out. By building a 200-square-meter greenhouse next to the biogas slurry tank and installing a culture tank, a transparent columnar plexiglass column, a columnar flexible plastic film bag, a multi-stage aeration filter device, a zooplankton enrichment and collection device, pipelines and inflatable facilities etc., to carry out resource utilization and purification treatment of pig farm biogas slurry.

Please refer to FIG. 1 , which is a schematic flowchart of a method for resource utilization of swine farm biogas slurry according to the present invention. A method for resource utilization of pig farm biogas slurry, the main method is that the fermented biogas slurry flowing out of the pig farm biogas tank is sequentially filtered through multi-stage aeration, inoculated with photosynthetic bacteria and cultured, inoculated with cladocera filter-feeding photosynthetic bacteria and collected branches Inoculation and cultivation of unicellular algae with cladocera and filtrate, inoculation of cladocera with filter-feeding unicellular algae and collection of cladocera, discharge or reuse of treated water up to standard, etc. In the process of treatment, photosynthetic bacteria are used to degrade the organic matter in the biogas slurry and generate bacteria, and then microalgae are used to absorb nutrients such as nitrogen and phosphorus in the biogas slurry and generate algal cells, and then use cladocera non-selective filter feeding during the treatment process The formed organic debris, photosynthetic bacteria and unicellular algae can be used for aquaculture or bait, so as to realize the resource utilization of pollutants in the biogas slurry.

Among them, the fermented biogas slurry flowing out of the biogas digester is firstly filtered by multi-stage aeration. The specifications of the stainless steel screen mesh used for multi-stage aeration filtration are 200 mesh, 300 mesh, 400 mesh and 500 mesh in turn. The screen mesh is inclined at a certain angle. Nano-aeration tubes are installed at the bottom of the screen to blow off part of the ammonia nitrogen in the biogas slurry under the action of aeration, while preventing the mesh of the screen from being blocked.

Among them, photosynthetic bacteria are inoculated into the biogas slurry that has been filtered by multi-stage aeration to degrade and absorb organic matter. The species of photosynthetic bacteria are Rhodopseudomonas, Rhodospirillum and Rhodobacter. The ratio of the initial inoculation amount to the biogas slurry filtered by multi-stage aeration is 3:7-5:5, and after 5-10 days of cultivation in a transparent plexiglass column or columnar flexible plastic film bag, a certain amount of biogas slurry inflow is maintained. Carry out continuous culture with the outflow speed of photosynthetic bacteria, and the inflow and outflow speed is adjusted according to the growth of photosynthetic bacteria.

Among them, part of the cultured photosynthetic bacteria can be directly harvested for aquaculture production according to needs, and the other part of the outflowing photosynthetic bacteria liquid enters the square culture tank, inoculates cladocera, and utilizes cladocera to non-selectively filter feed them. Organic detritus and photosynthetic bacteria, so as to remove organic and inorganic particles in the water body and improve the transparency of the water body. The species of Cladocera inoculated are Moinaaffinis of the genus Pleia, Daphniamagna of the genus Daphniamagna and Weevil flea Bosminalongirostris.

Wherein, the cultivated Cladocera can be enriched through the filter harvesting device, and the enriched Cladocera can be used as live bait for aquatic animal seedlings or ornamental fish, and can also be recycled for filter-feeding single-celled algae.

Among them, the biogas slurry that has been filtered by Cladocera once is inoculated with unicellular algae to absorb nutrients such as nitrogen and phosphorus in the water body. The algae species of unicellular algae are Chlorella, Oocystis, and Chlorella It belongs to the species of Chlorococcum and Scenedesmus, the ratio of the initial inoculum of single cells to the biogas slurry that has been filtered by Cladocera is 1:1~5, and it is carried out in a transparent plexiglass column or a columnar flexible plastic film bag After 5-10 days of aerated culture, maintain a certain biogas slurry inflow and single-cell algae liquid outflow speed to implement continuous culture. The inflow and outflow speed is adjusted according to the growth of single cells and the nitrogen and phosphorus content in the water.

Among them, part of the cultured algae liquid can be directly harvested for aquaculture production according to needs, and the other part of the outflowed algae liquid enters the square culture tank and is inoculated with Cladocera, using the non-selective filter-feeding characteristics of Cladocera for secondary feeding. Filter-feed the organic debris and single-celled algae in it to further purify the water body. The species of Cladocera inoculated are Moinaaffinis of the genus Pyrophora, Daphniamagna of the genus Daphniamagna, and elephants of the genus Elephantrum Nasal flea Bosminalongirostris.

Among them, the biogas slurry that has undergone the secondary filtration of cladocera can be treated and discharged after being tested to meet the sewage discharge standards for livestock and poultry breeding, or reused as flushing water for pig houses. If it does not meet the discharge standards, it can be treated Duplicate processing.

Implementation Effect:

In 2015, the pig farm biogas slurry resource utilization and purification treatment was carried out through the method of the present invention, and a total of about 450 cubic meters of biogas slurry was processed, of which 75 cubic meters of photosynthetic bacteria liquid, 50 cubic meters of single-cell algae liquid, and fresh branches were produced. 355 kg of horns, about 310 cubic meters of discharge water, the main water quality indicators of discharge water are as follows: chemical oxygen consumption<300mg/L, ammonia nitrogen<50mg/L, total phosphorus<5mg/L, pH6.8-7.5, Transparency > 40cm.

Compared with traditional methods, a method for resource utilization of pig farm biogas slurry has obvious advantages. The method for resource utilization of pig farm biogas slurry can use photosynthetic bacteria, unicellular algae and cladocerans generated in the process of biogas slurry treatment For aquaculture and bait, the pollutants in the biogas slurry can be utilized as resources by means of the food chain, which has the characteristics of low investment, low energy consumption, and can produce obvious economic and ecological benefits; traditional wastewater treatment projects can only reduce the amount of pollutants Emissions and emission intensity usually have little product output, which can only produce environmental, ecological and social benefits, and it is difficult to produce economic benefits. This mode of only investing but not producing results in enterprises being inactive in environmental protection investment, and the present invention couples sewage treatment with live bait production, not only can realize effective treatment of sewage, but also can reduce the cost of live bait production and realize environmental sustainability and resource recycling, in line with the national trend of developing ecological agriculture, green agriculture and circular agriculture;

Livestock and poultry breeding sewage is not only a serious source of pollution, but also a valuable resource. The invention introduces photosynthetic bacteria, microalgae and cladocera into the traditional livestock and poultry breeding sewage treatment process, and couples the pig farm biogas slurry purification and live bait production through the photosynthetic bacteria-microalgae-cladocera food chain, and utilizes the pig farm biogas slurry Medium and high concentrations of nitrogen, phosphorus, organic matter and other nutrient salts are used to cultivate photosynthetic bacteria and microalgae, and the cultured photosynthetic bacteria and microalgae are used to produce live bait through Cladocera filter feeding for animal breeding and production, thereby realizing environmental protection and efficient recycling of resources Use to ensure the sustainable development of production and ecology.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the method of the present invention, some improvements and supplements can also be made, and these improvements and supplements should also be considered Be the protection scope of the present invention.

Claims (8)

1. the method for natural pond, pig farm liquid recycling, it is characterized in that, the fermentation biogas liquid flowed out in digester of pig farm filters through multi-stage aeration successively, inoculation photosynthetic bacterium is also cultivated, inoculation cladocera filter food photosynthetic bacterium also collects cladocera, filtrate inoculation unicellular algae is also cultivated, inoculation cladocera filter food single-cell algae also collects cladocera and water discharge up to standard or reuse link after processing, first utilize the organism in the liquid of photosynthetic bacterium degraded natural pond in treating processes and generate thalline, micro-algae is utilized to absorb the nutritive salt such as nitrogen phosphorus in natural pond liquid and generate frustule afterwards, the organic debris formed in recycling cladocera non-selective filter food treating processes, photosynthetic bacterium and unicellular algae, the cladocera produced, photosynthetic bacterium, unicellular algae is used for aquaculture or bait, thus realize the recycling of pollution substance in the liquid of natural pond.

2. the method for natural pond, a kind of pig farm according to claim 1 liquid recycling, it is characterized in that, first the fermentation biogas liquid flowed out in digester of pig farm filter through multi-stage aeration, the stainless steel mesh specification that the multi-stage aeration adopted filters is followed successively by 200 orders, 300 orders, 400 orders and 500 orders, screen cloth tilts at an angle, installs nanometer aeration pipe in screen bottom, by the part ammonia-nitrogen desorption in the liquid of natural pond under the effect of aeration, prevent sieve mesh from blocking simultaneously.

3. the method for natural pond, a kind of pig farm according to claim 1 liquid recycling, it is characterized in that, photosynthetic bacterium is inoculated with degraded and absorption organism in the natural pond liquid that multi-stage aeration filters, the bacterial classification of photosynthetic bacterium is Rhodopseudomonas Rhodopseudomonas, rhodospirillum Rhodospirillum and red bacterium belong to the kind of Rhodobacter, the ratio that the initial inoculum of photosynthetic bacterium and multi-stage aeration filter natural pond liquid is 3:7 ~ 5:5, carry out cultivation in 5 ~ 10 days in transparent synthetic glass post or column flexible plastic film bag after, maintain certain natural pond liquid to flow into and photosynthetic bacteria liquid take-off rate implementation cultured continuously, the speed of inflow and outflow adjusts according to photosynthetic bacterium growth situation.

4. the method for natural pond, a kind of pig farm according to claim 1 liquid recycling, it is characterized in that, a cultured photosynthetic bacterium part is directly gathered as required for aquaculture production, after the photosynthetic bacteria liquid that another part flows out enters square cultivation tank, inoculation cladocera, utilize the organic debris in the non-selective filter Shiqi of cladocera and photosynthetic bacterium, thus the organic and particles of inorganic material in removal water body, promote water transparency, the kind of the cladocera inoculated is the seemingly close naked abdomen flea Moinaaffinis that naked abdomen flea belongs to, the Daphnia magna Daphniamagna that flea belongs to and the trunk flea Bosminalongirostris that trunk flea belongs to.

5. the method for natural pond, a kind of pig farm according to claim 1 liquid recycling, it is characterized in that, the cladocera cultivated is by filtering recovering device enrichment, and the cladocera of enrichment is used as the living bait of aquatic animal seedling or aquarium fish, is also cycled to used in filter food unicellular algae.

6. the method for natural pond, a kind of pig farm according to claim 1 liquid recycling, it is characterized in that, the natural pond liquid of food is once filtered through cladocera, inoculation unicellular algae is to absorb the nutritive salt such as nitrogen phosphorus in water body, the algae kind of unicellular algae is Chlorella Chlorella, egg capsule Trentepohlia Oocystis, the kind of Chlorococcum Chlorococcum and Scenedesmus Scenedesmus, single celled initial inoculum is 1:1 ~ 5 with the ratio of once filtering the natural pond liquid of food through cladocera, carry out 5 ~ 10 days air-charging incubation in transparent synthetic glass post or column flexible plastic film bag after, maintain certain natural pond liquid to flow into and single-cell algae liquid take-off rate implementation cultured continuously, the speed of inflow and outflow adjusts according to the content of single cells grown situation and Water phosphorus.

7. the method for natural pond, a kind of pig farm according to claim 1 liquid recycling, it is characterized in that, a cultured algae liquid part is directly gathered as required for aquaculture production, after the algae liquid that another part flows out enters square cultivation tank, inoculation cladocera, utilize the organic debris in cladocera nonselective filter food characteristic secondary filter drinking water body and unicellular algae, further purifying water body, the kind of the cladocera inoculated is the seemingly close naked abdomen flea Moinaaffinis that naked abdomen flea belongs to, the Daphnia magna Daphniamagna that flea belongs to and the trunk flea Bosminalongirostris that trunk flea belongs to.

8. the method for natural pond, a kind of pig farm according to claim 1 liquid recycling, it is characterized in that, through the natural pond liquid of cladocera secondary filter food, after meeting livestock and poultry cultivation sewage drainage standard after testing, carry out discharge of wastewater process up to standard or reuse and rush liquid dung as pig house, do not reach emission standard if detect, carry out re-treatment.