pondtechnology.com - BOG FILTERS

	BOG FILTERS Bogs, marshes, and other wetlands serve as a natural filtering system by supporting lush plant growth and large populations of microorganisms. The microorganisms break down organic matter into simple nutrients, and the plants extract the nutrients as food. Variations of this natural ecosystem can provide low-maintenance pond filtration while becoming an attractive addition to the pond environment.
	cross-section of molded bog filter showing how water enters the side reservoir, flows down to the bottom, and then flows up through a graded gravel fill
	MOLDED BOG FILTERS: Our molded bog filters consist of a plastic basin with an integral water distribution chamber built into the bottom and a water reservoir built into one side. The basin is buried flush with the ground surface and then filled with graded filter material (typically coarse gravel at the bottom, medium gravel in the middle, and fine gravel at the top) into which is planted nutrient-loving marsh vegetation. Water is pumped from the pond into the side reservoir (a bulkhead fitting is required), from where it flows by gravity under the basin, through a perforated plate, and up through the gravel and plant roots. The water then surfaces and spills back into the pond or into a waterfall that leads back to the pond. The graded filter material traps organic matter and provides enormous surface area for bacterial growth, while the plant roots extract the nutrients released by the bacteria.
	SIZES: We offer two sizes: a small bog (2.5 ft x 4 ft x 1.5 ft deep) for ponds up to 1500 gallons and a large bog (4 ft x 5 ft x 1.5 ft deep) for ponds up to 3000 gallons. Several of the large bogs can be used in parallel to filter larger ponds. We suggest a maximum water flow rate of 500 GPH for the small bog and 1000 GPH for the large bog. Following is the recommended fill for the small molded bog filter, listed from the bottom up. For the large molded bog filter, double each. 1 cubic foot of 3/4" to 1-1/2" gravel 2 cubic feet of 3/8" to 3/4" gravel 4 cubic feet of 1/8" to 3/8" gravel For enhanced filtration, ceramic filter can be substituted for some of the fine gravel. The top of the filter should be planted with plants that thrive in saturated soil, such as water iris, cattails, and rushes. If the edges of the bog are concealed with large rocks, the filter will be invisible after a month. Several times per year, the bog should be backwashed by pumping (or pouring) pond water onto the surface. This will flush accumulated organic matter from the bottom of the basin into the reservoir, where it can be removed with a small bucket or with a wet-and-dry vacuum. After three to five years, all the gravel should be removed and cleaned, and the bog should be rebuilt. Bog Filter, 1500 gallon, $240.00 Bog Filter, 3000 gallon, $320.00 Ceramic Filter Rock, 25 lbs, 24.00	small bog large bog
	SITE-BUILT BOG FILTERS: For filtration in larger ponds, site-built bog filters can be incorporated in the landscape. The bog surface area should be at least one-tenth the surface area of the pond. The bog is lined with a rubber pond liner; a network of perforated drain pipe is laid; and gravel is spread in the same proportions listed for the molded bogs. Water can be pumped under pressure into the pipe network, or it can be pumped to a distribution chamber from where it can flow through the bog by gravity.
	© 2004 Resource Conservation Technology Inc