Temporal interactions: seasonal effect on plant growth and concentration decrease of nitrogen and COD

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Local context in regions with concentrated animal feeding operations (CAFO)

In animal production, intensive production systems have been developed to increase animal production during green revolution. They improved the conversion ratio of feed to meat and the biosecurity of animal products.
However, negative effects of these systems were observed with several pollutions. During the production process, the quantity of livestock waste is higher than the recycling capability of nature. Ammonia (NH3), nitrous oxide (NO2) and methane (CH4) are released during the process of animal production and manure management. They induce air pollution. Intensive animal production also produces bad odor that can have negative effects on health. When high rates of organic effluents are spread on crop areas, leakages can induce water pollution through contamination by nitrates (NO3), phosphates (PO4), organic carbon (COD) and potassium (K+). Accumulation of copper (Cu), zinc (Zn) and xenobiotics in soils is also pollution.
Agriculture contributes to greenhouse gas emissions worldwide. Four-fifth of agriculture emissions is from livestock sector (Friel et al. 2009). Strategies to reduce negatives effect are proposed in many countries but their application is difficult because of economical competition between countries.
Brittany is the region with the highest animal production in France. Its intensive animal production system is an example of negative effects on the environment. Water consumption by these system is very high, and their wastewater added to mineral fertilizing pollutes the ecosystem (Morand et al. 2009). Pig production is particularly exposed to critics because of the bad odors generated by animal housing and slurry spreading.
“Concentrated animal feeding operations” (CAFO) is the American name for systems that are used for feeding the animal in intensive animal production. This system is effective to increase the animal production. However, CAFO has several negative impacts on the environment; such as air, soil and water pollution because the animal numbers increase without increasing the area of effluent recycling (Constance and Bonanno, 1999). Rule et al. (2005) explained that CAFO in pig building make poor air quality for worker, the community and farm production.
The development of these industrial systems is expected to continue because they allow increasing rapidly the animal production and supplying the food consumed by the developing towns.

Ecological engineering

Transformation processes are important when recycling fresh animal effluents into crop productions. We assume that the recycling efficiency of natural processes is higher when they are less disturbed (Odum, 1971). At the beginning, the animal effluents are too concentrated and too reactive to be directly recycled into crop productions. To improve the recycling efficiency, the animal effluents can be added with low dose, corresponding to natural fluxes of reactive organic matter in soils. If a high dose of organic matter is added to the soil, the animal effluents should be transformed so that the added organic matter is more stable, having similar properties as soil organic matter.
Earthworms have effective digestive system: common knowledge of vermicomposters say that they are supposed to transform each day approximately their weight of organic matter. When organic matter passes the digestive system, the biochemical reaction (the reactions associated to microorganisms) will increase the stability of the organic matter.
In aquatic systems, plants are important factor (Keffala and Ghrabi, 2005). They can absorb mineral forms of nutrients. They can reduce the velocity of liquid flow. This action provokes the sedimentation process of organic particles. The plant root is a habitat for microorganisms. The microorganisms have a major influence on nitrogen transformations through nitrification and denitrification. In freewater lagoons the water is exposed to solar radiation that can contribute to hygienization and increase the rate of some chemical reactions. The experiment of (Vymazal, 2002) with horizontal flow constructed wetland or that of (Brix and Arias, 2005b) with vertical ones showed that ecological systems were efficient for chemical nutrient removal.
Earthworms and plants can be observed easily by farmers. Thus, their use in biological treatment systems is not only to contribute to the treatment, directly or indirectly, but also to help the management, as bioindicators.

Vermicomposting and vermifiltration

Vermicomposting is a biological transformation of organic wastes. Earthworms can stabilize organic wastes (Sharma et al. 2005). Earthworms are important actors of the processes in this part (Atiyeh et al. 2000). Earthworms and animal manure can help to recycle industrial organic by-products (Garg and Kaushik, 2005).
Vermifilter earthworms need organic matter as their food. The experimental results of Pramanik et al. (2007) demonstrated vermicomposting as an alternate technology for the management of biodegradable organic wastes. Decrease in chemical elements is achieved within the vermifilter. The species that are used for vermifilter are epigeic earthworms such as Eisenia fetida and Eisenia andrei. These species are often used for a suitable technology for the decomposition of different types of organic wastes (Kaviraj and Sharma 2003, Garg et al. 2006). Vermicompost is also used to filter wastewater and transform the organic matter (Taylor et al., 2003).
Metals in wastewater are absorbed by vermicompost (Urdaneta et al. 2007). Earthworms influence the absorption process. In this case, earthworms work as ecological engineers. In vermifilter, the ecological engineering function of earthworms is used to reduce the pollutions effects of pig slurry. Earthworms make several pores in vermifilter. It promotes air diffusion and the reactions in vermifilter are quite aerobic. It avoids the fermentation that produces polluting gases such as methane and ammonia. The porosity also helps the transfer of liquid and organic matter. Removal of earthworm casts will avoid the accumulation organic matter that could fill the free air space and make the environment toxic.
Transformation process of vermicomposting resulted in significant reduction in C:N ratio and increase in nitrogen phosphorus, potassium, and calcium concentrations (Kaushik and Garg 2004). Gaseous losses can be polluting gases. It should be controlled to avoid pollution transfer when transforming organic matter. Methane (CH4) atmospheric concentration has doubled in the past several hundred years to the present 1.7 ppm which is rising by around 4 ppb/yr. It is 18 around percent of enhanced global greenhouse effect. Nitrous oxide (N2O) atmospheric concentration is approximately 311 ppb and rising by around 0.75 ppb yr (Frederickson et al., 2006). Vermicomposting could contribute to greenhouse gas emissions (Frederickson and Howell 2003). Nitrous oxide fluxes observed in winter (week 60) were 3.2 ± 0.3 mg m–2 h–1 (unheated beds), 1.8 ± 0.3 mg m–2 h–1 (heated beds). Emissions during summer (week 80) were 20.1 ± 3.0 mg m–2 h–1 (unheated beds), 21.3 ± 2.8 mg m–2 h–1 (heated beds). No relationship between earthworm density and nitrous oxide flux was found for the large-scale beds. However, in a subsequent laboratory experiment, nitrous oxide emissions were positively correlated with earthworm density (R2 = 0.76).
However, despite these observations, Edwards & Arancon (2008) consider that it is not possible that vermicomposting contributes significantly to global warming, on the basis of the US example. In U.S in 2006, 84 percent of greenhouse gas emissions were carbon dioxide (CO2), 7.8 percent were methane (CH4),and 5.2 percent were nitrous oxide (N2O). The N2O emissions, 72 percent came from managing agricultural crop residues, 3.9 percent from animal manures and 0.5 percent from all forms of composting, including vermicomposting.
The vermifilter input is diluted pig slurry. It has several functions. First function of pig slurry is organic matter source. If there is not enough pig slurry, the system in vermifilter will not function normally because the feed is not sufficient to meet the needs of the earthworm population. On the contrary, if the input of pig slurry is too high, the excess of fresh organic matter will transform into anoxic compounds and it will induce toxicity for vermifilter earthworm population. In this case, the effect of pig slurry is a source of organic pollutants. Therefore a critical knowledge for the design and management of the vermifilter is to define the optimal quantity of pig slurry as its input. If the quantity of pig slurry is less than earthworm ingestion capability, the earthworm abundance will decrease slowly, organic matter transformation process will work slowly, water movement will increase if earthworm activity induces higher porosity and free air space, and water biotreatment will be stable. On the contrary, if quantity pig slurry is more than earthworm ingestion capability, the earthworm abundance will decrease rapidly, because organic matter transformation will induce anoxic conditions, and there will be earthworm mortality because of the anoxic environment and polluting gases can be emitted such as ammonia (NH3) or methane (CH4).
Once the input of vermifilter is defined, critical knowledge concerns the transformation of organic matter. Pig slurry is a source of chemical elements. When crossing the vermifilter the concentration of nutrients change and the chemical nature of nutrients also changes. The same concepts of optimal input and transformations can be applied to the constructed wetlands. The detailed knowledge of all transformation processes occurring in this experiment, including microbial, chemical and physical.

Different types of lagooning

Constructed wetland is effective technology for wastewater treatment (Kadlec and Knight, 1996). In tropical region, the experiment of (Kivaisi, 2001) found constructed wetland was potential technology for wastewater treatment. In subtropical region (Kadlec, 2003) found the same result. Several researchers used constructed wetland for agriculture wastewater treatments (Jordan et al. (2003); Kovacic et al. (2006); Healy, Rodgers and Mulqueen (2007)). Constructed wetlands are often used as alternates to or components of conventional nutrient management practices to reduce or eliminate contaminant and nutrient from animal wastewater (Lansing and Martin, 2006; Dunne et al., 2005; Verhoeven and Meuleman, 1996; Tanner et al. 1995). The experiment of Lavrova and Koumanova (2007) showed that constructed wetland could reduce nutrients of piggery
The wastewater will be treated by physical filtration, chemical adsorption on organic particles, and biological transformations by microbial populations and absorption by macrophytes. Although the plants are growing in these constructed wetlands, they are not the first factors that influence the decrease of chemical elements. They help to monitor the processes that are dominant, and to check that the transformations are stable. The treatment functions of a wetland can be optimized depending on the season (Gerke et al., 2001).
For nitrogen specifically, the complexity of nitrogen removal in water systems, including water, plants, sediments, fauna, and microbes with specific seasonal effects and nutrition dependencies, have been extensively reviewed and discussed recently by Birgand et al. (2007).
According to U.S. Environmental Protection Agency (EPA) (1999) and (Vymazal 2007), there are three types of constructed wetlands.

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Constructed wetland with free floating plants (FFP)

In this case, basins are covered with floating aquatic plants (Figure 1). It has open water areas. The free floating plants can be water hyacinth (Eichhornia crassipes), duckweed (Lemna spp., Spirodela spp., Wolffia spp.), water fern (Azolla caroliniana and Salvinia rotundifolia) or water lettuce (Pistia stratiotes). Also common are rooted plants growing in a floating form, including pennywort (Hydrocotlyle spp.), water lily (Nymphaea spp.), frog’s bit (Limnobium spongia), spatterdock (Nuphar spp.), and pondweed (Potemogeton spp.).
In the open water source system like FFP, volatilization works effective as removal elements. This system is lacking soil process. Plant uptake is the major removal mechanism. Ammonification is effective in this system. The removal level by denitrification is medium.
The major mechanism of P removal is plant uptake. The microbial uptake is low. The adsoption and soil accretion has very small influence on P removal (Vymazal 2007).

Free water surface (FWS)

Constructed wetlands are designed using a combination of open-water areas and emergent vegetation. These wetlands are constructed wetlands that provide wastewater treatment through flocculation and sedimentation during the flow of wastewater through stands of aquatic plants growing in shallow water. In some FWS wetlands, there are also open areas where aerobic bio-oxidation complements the physical removal processes (Figure 2). FWS systems resemble natural wetlands in function and appearance. FWS systems have also been termed “surface flow systems.”
Denitrification is the major process of nitrogen removal in this system. Volatilization and nitrification are effective in this system. Plant uptake does not have an important role in nitrogen removal. The soil processes are very limited (Vymazal 2007).

Constructed wetland with subsurface flow (SF)

This type of systems provide wastewater treatment within a filter media. Water is not directly exposed to the atmosphere but may be slightly influenced by the roots of surface vegetation. Subsurface flow (SF) wetlands systems also have been termed rock reed filters, submerged filters, root zone method, reed bed treatment systems, and microbial rock plant filters. Gravel beds rather than hydric soils are the support media for wetland plants; as a result, the systems are not truly wetlands.
If the flow of liquid is horizontal, the system is called Horizontal subsurface flow (HSF, Figure 3). If the liquid flows from up to bottom, the system is called Vertical subsurface flow (VSF, Figure 4).

Solid (vermicompost)

For each treatment, a sample of the vermifilter media was taken on days 18th September, 30th September and 7th October. Samples were taken after mixing the vermicompost in each mesocosm. In the running vermifilter, the vermicompost was also mixed every week. Thus it is assumed that the sampling and mixing operation did not alter the representatives of the experiment. Samples were also taken at the surface of the mesocosm (0-10 cm).
The sampling procedure is shown in Figure 17. On sampling days, there were not pig slurry applications. Each container was weighted. The surface solid samples were taken. The tray (11 cm x 10cm x 6 cm) was used for surface sampling.
The vermicompost was taken out from container. The vermicompost was gently mixed to preserve the earthworms. Vermicompost was divided into two parts. The operation (mix-divide) has been done three times.
One-half part of vermicompost was returned to the container and the other part was mixed. This operation (mix-divide) was repeated for each container until the quantity of material in a sample (about 2 l) was obtained. Three trays (11 cm x 10 cm x 6 cm) were used for mix samplings. The part of vermicompost that was not used as mix solid sampling would be returned to container. After the sampling, the new quantity of vermicompost was weighed to have the initial mass of the next period, the container was progressively filled, the thermocouple was installed horizontally around 20 cm below the surface (e.g. 21±2 cm on 11th September 2009), finally the surface was slightly compacted to ensure homogenous infiltration of the wastewater.
The sample was divided among 3 trays (approximately 400 mL per tray), and each tray was weighed. One tray was conserved in a deep freezer (-18°C) for further analysis. One tray was used for earthworm counting. One tray was used for dry matter analysis, and then its contents was ground and analyzed for C and N by INRA (Institut National de la Recherche Agronomique) in Rennes.

Table of contents :

Part 1: Vermifiltration process: optimal input and gaseous emissions.
Chapter 1: Optimal input of pig fresh liquid manure during vermifiltration
1. Résumé du chapitre 1 : Intrant optimal de lisier frais d’un élevage de porcs pour la lombrifiltration
2. Abstract
3. Introduction
4. Hypothesis
5. Material and methods
5.1. Experimental site
5.2. Pig slurry application
5.3. Sampling
5.3.1. Solid (vermicompost)
5.3.2. Liquid
5.3.3. Earthworms
5.4. Analytical methods
5.4.1. Statistical analysis
5.4.2. Mass balance
5.4.3. Calculation of the porosity
6. Results
6.1. Abundance of population and biomass
6.2. Cluster analysis
6.3. Evolution of free air space
6.4. Evolution of C and N contents
7. Discussion of hypothesis
7.1. Existence of an optimum
7.2. Speed of evolution of the earthworm population
7.3. Distribution of the earthworm population in the vermifilter
7.4. Clogging
8. Conclusions
9. Knowledge application to design and management
Chapter 2: Effect of input dose and earthworm presence on gaseous emissions during vermifiltration
1. Résumé du chapitre 2 : effet de la dose et de la présence des lombriciens sur les émissions gazeuses durant la lombrifiltration
2. Abstract
3. Introduction
4. Hypothesis
5. Material and methods
5.1. Experimental site
5.2. Containers
5.3. Pig slurry application
5.4. Sampling
5.4.1. Solid (compost)
5.4.2. Liquid
5.5. Measurements
5.5.1. Temperature
5.5.2. Water and dry matter input and output
5.5.3. Earthworms
5.5.4. Gaseous emissions
5.6. Data processing
6. Results
6.1. Liquid budget
6.1.1. Liquid input
6.1.2. Liquid output
6.1.3. Net liquid input of mesocosm
6.1.4. Water input
6.1.5. Water output
6.1.6. Net water input in mesocosms
6.1.7. Dry matter content of the liquids
6.1.8. Dry matter input of mesocosms
6.1.9. Dry matter output of mesocosms
6.1.10. Net dry matter inputs of mesocosms
6.1.11. Conclusions concerning the liquid input
6.2. Mesocosm weights
6.2.1. Water content of the vermifilters
6.2.2. Wet weight of the mesocosms
6.2.3. Mass of water in the mesocosm
6.2.4. Dry matter of mesocosm
6.2.5. Conclusions the vermifilter media
6.3. Mesocosm temperatures
6.4. Gaseous emissions
6.4.1. Methane (CH4) Emission
6.4.2. Ammonia emission
6.4.3. Carbon dioxide emission
6.4.4. Water emissions
6.4.5. Nitrous oxide emission
6.5. Earthworm populations
6.5.1. Earthworm abundance
6.5.2. Earthworm biomass
6.5.3. Conclusions concerning earthworms
7. Discussion of hypothesis
7.1. Representativity of the observations
7.2. Confirmation of the existence of an optimal input of liquid and organic matter of the mesocosms
7.3. Heat transfer
7.4. Effect of earthworms on mixing the input matter and on liquid circulation
7.5. Effect of earthworms on maintaining a connected free air space inside the porous media and on the resulting gas emissions
7.6. Resulting effect of earthworms on gaseous emissions
7.6.1. Confirmation of methane sink by earthworm casts
7.6.2. Negligible ammonia emission
7.6.3. Carbon dioxide emission
7.6.4. Nitrous oxide emission
7.6.5. A new hypothesis to explain the effect of earthworms on either increase or decrease of nitrous oxide emission
7.7. Potential impact of vermifiltration of pig fresh manure on global warming
8. Conclusions
9. Knowledge application to design and management
Part 2: Bio recycling systems: optimal interactions between subsystems including vermifiltration, macrophyte lagooning, and constructed wetlands
Chapter 3: Spatial interactions: biological filtration of liquid manure and water recycling through vermifiltration and macrophyte lagooning
1. Résumé du chapitre 3 : interactions spatiales, filtration biologique d’un effluent liquide et recyclage de l’eau par lombrifiltration et lagunage à macrophytes
2. Abstract
3. Introduction
4. Hypothesis
5. Material and methods
5.1. Experimental design
5.2. Measurements
5.3. Mass balance estimate
5.4. Data processing
6. Results
6.1. Concentration of nutrients in the water
6.1.1. COD evolution
6.1.2. Total N, total P and total K evolution
6.1.3. NH4 evolution
6.1.4. Evolution of NO3 and NO2
6.2. Concentration of nutrients in sludge and plants
6.3. Nutrient retention in sludge and plants
7. Discussion of hypothesis
7.1. Removal of macronutrients
7.1.1. Decrease in nitrogen
7.1.2. Decrease in phosphorus
7.1.3. Decrease in potassium
7.1.4. Removal of COD
7.1.5. Role of precipitation and evaporation
7.2. Variability of concentration measurements
7.3. Nitrification-denitrification, sedimentation and plant uptake
8. Conclusions
9. Knowledge application to design and management
Chapter 4: Temporal interactions: seasonal effect on plant growth and concentration decrease of nitrogen and COD
1. Résumé du chapitre 4 : interactions temporelles : effet de la saison sur la croissance des plantes et l’abatement d’azote et de DCO
2. Abstract
3. Introduction
4. Hypothesis
5. Material and methods
5.1. System design
5.2. Experimental design
6. Results
6.1. Removal of COD
6.2. Removal of total nitrogen
6.3. Nitrate evolution
6.4. Plant growth
7. Discussion of hypothesis
7.1. Removal of COD
7.2. Variation in removal of total nitrogen and nitrate
7.3. Plants, seasons and chemical elements
7.4. Role of precipitation and evaporation
8. Conclusions
9. Knowledge application to design and management
General discussion
1. Comparison of efficiency in « station expérimentale » and “prototype”
1.1. Size effect
1.2. Recycling effect
2. Hypothesis on gaseous emissions from lagooning
2.1. Sample places
2.2. Size among components
2.3. Dose application
2.4. Calculation for N2O
2.5. Hypothesis for CO2, CH4 and NH3
3. “Treating” or “Recycling”


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