Wetland Phosphorus Cycle

Transcription

1 Diffusion Sedimentation Diffusion allows dissolved forms of Phosphorus to be transferred from the incoming surface water into the soil and back again on occasion. A concentration gradient is what allows different forms of phosphorus to move into and back out of the sediment. This concentration gradient causes phosphorus to move from a region of high concentration to low concentration resulting in the back and forward movement of phosphorus from the overlying water to the sediment or vice versa. The shallow, slow moving water found in wetlands allows for particulate matter (inorganic and/or organic sediment) floating in the water column to settle out and collect on the surface of the soil, in a process known as sedimentation. This settling process allows for the removal of contaminants from the water. Wetland Phosphorus Cycle Plant uptake Plants which are present in wetlands typically root into the soil or float around in the overlying water. Inorganic phosphorus, primarily orthophosphate, is then taken up by these plants, ultimately removing the phosphorus form the water where it is stored in the plants. Microorganisms which live within wetlands, utilize organic carbon for energy by breaking down organic matter, including plant detritus, organic sediments and peat. Organic phosphorus compounds are broken down into smaller organic molecules including particulate and dissolved molecules. In the end, these molecules are broken down into inorganic phosphate (orthophosphate) which can either be utilized as energy by the microorganisms or released back into the soil or water. Sorption Litterfall Dead plant tissue such as leaves and stems fall from plants that live in and around the wetland where they collect at the sediment/ water interface. The dead plant tissue sometimes contains inorganic phosphorus which was previously removed from the water through processes like plant uptake. The result is the accumulation of dead plant tissue (detrius) containing phosphorus at the bottom of the wetland in the process known as litterfall. Decomposition Burial and peat accretion Dead plant tissue (detrius) which has accumulated at the sediment/ water interface gradually is buried and incorporated into the soil. This buried material represents the portion of organic material that is more resistant to decomposition. Over time, the organic material ages while it decomposes and compresses, forming peat in the process known as peat accretion. This formation of peat allows for the long term storage Sorption involves two processes. The first process is the adsorption of inorganic phosphate by clays and iron or aluminum oxides present in the soil. The second process involves the retention of inorganic phosphate (PO43-) with either iron and aluminum oxides or dissolved calcium, to form solid compounds in the sediment or water column. These processes allow for unstable inorganic phosphorus to become stable so they can then be stored for long periods of time in the process known as sorption.

2

3 The Future of Constructed Wetlands for Wastewater Treatment Haliburton Hatcheries Facts: Treating aquaculture wastewater using constructed wetlands at the Haliburton Fish Hatcheries will provide valuable information and insight for now and for the future. The efficiency and effectiveness of biological, chemical, and physical wetland processes in treating wastewater will be established. Alternative methods for treating wastewater will be begin to develop based on the findings and information gathered from this aquaculture treatment wetland. The surrounding community will benefit from the educational opportunities provided from this constructed wetland which they can carry onto future generations. Since 1998, the Haliburton Fish Hatchery has raised 200,000 Rainbow and Brook Trout, 40,000 Walleye, and 70,000 Haliburton Gold Lake Trout. Constructed Wetland at the Haliburton Hatcheries Treating Aquaculture Wastewater using Constructed Wetlands With the help of the scientific community and the public, the treatment of aquaculture wastewater through wetland processes can be made public in efforts of broadening the knowledge on wastewater treatment alternatives. With any luck, one day constructed wetlands such as this, may replace wastewater treatment plants of the present. Haliburton Highlands Outdoor Association P.O. Box 184 Haliburton, Ontario K0M 1S0 Phone: 705) Fax: (705) Website: "Water should not be judged by its history, but by its quality" - L. Van Vuuren

4 How are Fish Hatcheries and Wetlands related? As fish grow they excrete organic materials into the water. This is generally considered aquaculture wastewater, similar to human wastewater. If increased amounts of wastewater enters into natural rivers and streams without treatment then elevated algal levels and decreased oxygen levels can occur. Ultimately, the same effect can occur when human wastewater is not treated before entering into the environment. Wetlands aid in the treatment of aquaculture wastewater by using biological, physical, and chemical processes to clean the water. Wetlands Clean Aquaculture Wastewater Typical plant species found in wetlands such as the common reed (Phragmites australis), cattail (Typha spp.), and bulrush (Scirpus spp.) allow microbes such as bacteria, fungi, algae, and protozoa to attach and live on their exposed stems, leaves, and roots. A symbiotic association between the plant and the microbe occurs in which the plant is provided with an increased ability to capture water and elements esential to the plants growth such as phosphorus, zine, manganese, and copper. In return, the plant provides the microbe with carbohydrates and vitamins essential for the microbes growth. Aquaculture wastewater contains nutrients, metallic ions, and other compounds in which microbes modify to obtain nutrients and energy for carrying out their life cycles. The Common Wastewater Treatment Method The treatment of wastewater generated by humans is treated using wastewater treatment plants located in each community. One, two, or even three treatment stages are required before wastewater can be discharged back into the surrounding area for consumption. The first stage, known as primary treatment, allows the solids in the wastewater to settle to the bottom where it can be collected and disposed of. (either in a landfill or an incinerator). Primary treatment uses a series of pools and screens which settles the wastewater enough to separate solids from solution. At best, primary treatment might remove half of the solids, organic materials and bacteria from the water. If this is the only treatment stage for the water then chlorine must be used to kill remaining bacteria. Secondary treatment of wastewater removes organic materials and nutrients using bacteria. Large tanks contain bacteria which actively take in nutrients. The bacteria which have accumulated amounts of nutrients are then removed from the wastewater in settling tanks. Once secondary treatment is completed, 90% of all solids and organic materials are removed. The third and final stage of wastewater treatment uses chemicals to remove phosphorus and nitrogen from the water. It should be noted that in wetlands, soil bacteria take the place of chemicals in removing phosphorus and nitrogen from the water. Chlorine is further added to the water to kill all remaining bacteria before the discharge of the water. Managing Water Quality in Canada Health Canada sets the guidelines for Canadian drinking water based on various contaminants known to be present. Although Health Canada sets the guidelines, drinking water is a provincial, territorial and municipal governments responsibility. It is their responsibility to inform the public about pollution risks related to recreational uses of water in efforts of keeping public water safe. The collection and analyzation of water samples are compared to the Canadian drinking water quality guidelines to ensure the water in each jurisdiction is safe to use. From the Canadian drinking water quality guidelines, provincial, territorial and municipal governments form water quality objectives and standards for their regions. The Health Canada water quality guidelines specify limits for substances and describe conditions that affect drinking water quality. Regionally established water quality objectives and standards specify the concentrations of substances allowable in water bodies. A water quality safety test must meet both the regulations, objectives, and standards outlined by Health Canada and setup by regional governments in order to pass the test.

5 Ammonification (Mineralization) The transformation of organic nitrogen into ammonia is known as ammonification or nitrogen mineralization. Bacteria are typically responsible for the breakdown and decomposition of nitrogen-based organic tissues consisting mostly of dead organic materials. These bacteria and various fungi incorporates the nitrogen into amino acids and proteins and releases the remaining nitrogen into the soil water where it becomes ammonium ions (NH 4 + ). The amino acids and proteins which are produced, are taken up by plants to synthesis plant protein enabling them to grown. Nitrification The oxidation of ammonium ions (NH 4 + ) by bacteria into nitrate ions (N 2 - ) is known as nitrification. Once the nitrate ions are formed they can then be taken up by plants, allowing them to grown. Denitrification Denitrification invovles the reduction of nitrate (N0 3 - ) into volatile forms of nitrogen like nitrogen gas (N 2 ) and nitrous oxide (N 2 0) which are then released into the atmosphere. The removal of nitrogen in various forms into the atmosphere in the process of denitrification occurs in sediments of wetlands with the help of denitrifying bacteria. Wetland Nitrogen Cycle Nitrogen Fixation The replenishment of nitrogen in the soil occurs primarily as a result of nitrogen fixation carried out by specialized bacteria. Nitrogen fixation is the process in which atmospheric nitrogen (N 2 ) is reduced to ammonium ions (NH 4 + ). This reduction allows ammonium ions to become available for transfer to carbon-containing compounds to produced amino acids and other organic nitrogen-containing compounds. Nitrogen fixation is especially important because it is a key process in which all living things depend. Ammonia Volatilization Ammonia present in the sediments of a wetland can sometimes become gaseous at which time they become unstable. Ammonia gas which is an unstable form of nitrogen can be easily released to the atmosphere in the process of ammonia volatilization. The ability of ammonia to become unstable tends to increase as the temperature of the water and subsequent wetland becomes warm. Nitrogen Assimilation The assimilation of inorganic nitrogen (N0 3 and NH 4 + ) into organic nitrogen compounds is known as nitrogen assimilation. Initially, the conversion of nitrate (NO 3 - ) to nitrite (N0 2 - ) occurs which is then followed by a reduction to ammonia (NH 4 + ) by nitrite reductase. The ammonia is incorporated into glutamine as an amino nitrogen which is then transferred to 2-oxoglutarate to form two molecules of glutamate by glutamate synthase. Nitrogen assimilation allows for inorganic nitrogen present in the sediment to be converted into organic nitrogen which can be used by plants and organisms in the water of the wetland. Nitrate >Nitrite >Ammonia >Glutamine >Glutamate (NiR) (GoGAT) There are two enzymes which help to catalyze the overall pathway which include: nitrite reductase (NiR) and glutamate synthase (GoGAT)

6

7 Primary Applications of Wetland Water Treatment Industrial: Constructed Wetlands for De-Icing Fluid Treatment, Edmonton Alberta -Pollutants found in stormwater runoff at airports, including surface and aircraft de-icing/anti-icing glycols can be treated and removed to low levels in well-designed constructed wetland systems. The Edmonton International airport uses a 2.7ha constructed wetland to remove up to 230,000m3 of glycol-contaminated runoff anually. Aquaculture: Rosewall Fish Farms Constructed Wetland, Coral Creek BC -111m3/day of salmon hatchery wastewater is treated using constructed wetlands before it is discharged. Haliburton Hatcheries Facts: How are Fish Hatcheries and Wetlands related? Since 1998, the Haliburton Fish Hatchery has raised 200,000 Rainbow and Brook Trout, 40,000 Walleye, and 70,000 Haliburton Gold Lake Trout. Constructed Wetland at the Haliburton Hatcheries Treating Aquaculture Wastewater using Constructed Wetlands Institutional: Combination Peat Filter and Constructed Wetland, Forteau Newfoundland -The connection of an existing septic system to a combination natural peat filter and constructed wetland wastewater treatment system has taken place allowing each system to complement each other in the harsh landscape which they operate in. The wetland operates most efficiently in warmer weather, while the locally available sphagnum peat moss excels at treatment in colder weather. Municipal : Constructed Wetlands, Cobalt ON -The Town of Cobalt is undertaking a five year research program with the Ministry of the Environment to demonstrate the effectiveness of constructed wetland technology even under extreme northern Ontario climatic conditions. Agricultural: Mushroom Farm Leachate Treatment Wetland, Blenheim ON - Irrigation leachate water used to irrigate mushrooms, barn cleaning run-off and run-off from outdoor composing toilets are treated using constructed wetlands with water being directed back into the barns for re-use in irrigation and barn cleaning. Water in excess of re-use is used in the compost making process for mushroom growing media Residential: Curve Lake PeatLand Sewage Treatment Systems, Curve Lake First Nations -A constructed wetland system was designed for a daily flow rate of 14,850 L/day to treat wastewater from 27 bedrooms of a multi-residence building. The system combines constructed wetland technology and peat filtration. Haliburton Highlands Outdoor Association P.O. Box 184 Haliburton, Ontario K0M 1S0 Phone: 705) Fax: (705) info@hhoa.on.ca Website: "Water should not be judged by its history, but by its quality" - L. Van Vuuren Fish hatcheries rely on the growth of fish and therefore many chemicals are used to promote growth and reduce disease in fish. As fish grow they excrete organic materials into the water they live in typically called aquaculture wastewater. However, aquaculture wastewater is not only fecal matter from the fish, it can also include chemical additives used in aquaculture including: antibiotics to control diseases; pesticides to control parasites; hormones to induce spawning; anesthetics to immobilize fish during transport and handling; and pigments, vitamins, and minerals which promote rapid growth and desired qualities in the fish. If increased amounts of aquaculture wastewater enters into freshwater lakes and streams without treatment then elevated algal levels and decreased oxygen levels can occur. With that said, wetlands can treat aquaculture wastewater by means of biological, physical, and chemical processes.

8 Wetlands Clean Aquaculture Wastewater Typical plant species found in wetlands such as the common reed (Phragmites australis), cattail (Typha spp.), and bulrush (Scirpus spp.) allow microbes such as bacteria, fungi, algae, and protozoa to attach and live on their exposed stems, leaves, and roots. A symbiotic association between the plant and the microbe occurs in which the plant is provided with an increased ability to capture water and elements esential to the plants growth such as phosphorus, zine, manganese, and copper. In return, the plant provides the microbe with carbohydrates and vitamins essential for the microbes growth. Aquaculture wastewater contains nutrients, metallic ions, and other compounds in which microbes modify to obtain nutrients and energy for carrying out their life cycles. The modification of compounds produces alternative forms of the initial pollutant which is then lost to the atmosphere (eg. denitrification), accumulated in wetland soil (eg. phosphorus), or taken up and stored in plants. This modification of compounds by microbes allows for the actual treatment and cleaning of the wastewater. Aside from nutrient removal, wetlands also remove bactiera and protozoans typical of aquaculture wastewater by attaching them to suspended solids that are then trapped by wetland vegetation. Overtime, the bacteria will die as a result of remaining outside their host organisms, through degredation by sunlight, or from low ph of wetland water. Common Wastewater Treatment Method The treatment of wastewater generated by humans is treated using wastewater treatment plants located in each community. One, two, or even three treatment stages are required before wastewater can be discharged back into the surrounding area for consumption. The first stage, known as primary treatment, allows the solids in the wastewater to settle to the bottom where it can be collected and disposed of. (either in a landfill or an incinerator). Primary treatment uses a series of pools and screens which settles the wastewater enough to separate solids from solution. At best, primary treatment might remove half of the solids, organic materials and bacteria from the water. If this is the only treatment stage for the water then chlorine must be used to kill remaining bacteria. Secondary treatment of wastewater removes organic materials and nutrients using bacteria. Large tanks contain bacteria which actively take in nutrients. The bacteria which have accumulated amounts of nutrients are then removed from the wastewater in settling tanks. Once secondary treatment is completed, 90% of all solids and organic materials are removed. The third and final stage of wastewater treatment uses chemicals to remove phosphorus and nitrogen from the water. It should be noted that in wetlands, soil bacteria take the place of chemicals in removing phosphorus and nitrogen from the water. Chlorine is further added to the water to kill all remaining bacteria before the discharge of the water. The Future of Constructed Wetlands for Wastewater Treatment Treating aquaculture wastewater using constructed wetlands at the Haliburton Fish Hatcheries will provide valuable information and insight for now and for the future. The efficiency and effectiveness of biological, chemical, and physical wetland processes in treating wastewater will be established. Alternative methods for treating wastewater will be begin to develop based on the findings and information gathered from this aquaculture treatment wetland. The surrounding community will benefit from the educational opportunities provided from this constructed wetland which they can carry onto future generations. Managing Water Quality in Canada Health Canada sets the guidelines for Canadian drinking water based on various contaminants known to be present. Although Health Canada sets the guidelines, drinking water is a provincial, territorial and municipal governments responsibility. It is their responsibility to inform the public about pollution risks related to recreational uses of water in efforts of keeping public water safe. The collection and analyzation of water samples are compared to the Canadian drinking water quality guidelines to ensure the water in each jurisdiction is safe to use. From the Canadian drinking water quality guidelines, provincial, territorial and municipal governments form water quality objectives and standards for their regions. The Health Canada water quality guidelines specify limits for substances and describe conditions that affect drinking water quality. Regionally established water quality objectives and standards specify the concentrations of substances allowable in water bodies. A water quality safety test must meet both the regulations, objectives, and standards outlined by Health Canada and setup by regional governments in order to pass the test. With the help of the scientific community and the public, the treatment of aquaculture wastewater through wetland processes can be made public in efforts of broadening the knowledge on wastewater treatment alternatives. With any luck, one day constructed wetlands such as this, may replace wastewater treatment plants of the present.