Property, plant and equipment and construction in progress (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment, Gross	$ 106,898,952	$ 106,847,798
Less accumulated depreciation	47,905,546	42,662,688
Property, plant and equipment, net	58,993,406	64,185,110	55,923,731
Construction in progress	2,612,800	141,204	249,300
Land [Member]
Property, Plant and Equipment, Gross	3,223,361	3,223,361
Building [Member]
Property, Plant and Equipment, Gross	17,751,797	16,732,298
Plant and Equipment [Member]
Property, Plant and Equipment, Gross	57,635,523	58,758,920
Distribution Systems [Member]
Property, Plant and Equipment, Gross	24,213,390	24,099,566
Furniture and Fixtures [Member]
Property, Plant and Equipment, Gross	2,644,900	2,492,913
Vehicles [Member]
Property, Plant and Equipment, Gross	1,182,782	1,283,037
Leasehold Improvements [Member]
Property, Plant and Equipment, Gross	228,007	222,829
Lab Equipment [Member]
Property, Plant and Equipment, Gross	$ 19,192	$ 34,874

The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

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Gross amount of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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- Definition

Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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