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products from influent wastewater. Because the nitrogen associated with the ammonia molecule is easily available to the microorganisms, there should be no ammonia present in the treated water entering the wetland system because the ammonia will be converted to NOx by the microorganisms. This fact was confirmed in discussions with County Division of Utility Services personnel. Therefore, any TKN that might enter the canal from the WRWWTF wetland system will be comprised solely of organic nitrogen, which is very difficult for plants to utilize. Figure 4 clearly shows the TKN concentration decreases as the water travels toward the Lateral C Canal. This indicates the TKN is either being diluted by other water inputs or else a significant portion of the TKN is in the ammonia form. If the latter case is true, canal vegetation is removing the ammonia nitrogen as the water flows east, thereby reducing the TKN value. Ammonia in water is generally associated with septic tank effluent or livestock waste. Average TKN concentration decreases 0.31 mg/I From Sample Point B to Sample Point C. Concentrations decrease another 0.70 mg/I from Sample Point C to Sample Point D and they drop 0.48 mg/I between Sample Point D and Sample Point E. The average TKN reduction from Sample Point B to Sample Point E was 1.49 mg/I. The average TKN at Sample Point E is 0.22 mg/I higher than that measured at Sample Point F, indicating the 8th Street Canal west of the Lateral C Canal has a greater TKN loading than the canal section east of the Lateral C Canal. TKN Summary • TKN is composed of ammonia nitrogen and organic nitrogen, with the ammonia nitrogen being readily available to plants while the organic nitrogen component is not. • The average TKN concentration drops as the water flows east into the Lateral C Canal, and it is 3.06 times greater at Sample Point B than at the Study Area discharge at Sample Point E. • The highest average TKN concentrations appeared at Sample Point B, which is opposite the WRWWTF wetland. However, all TKN that might leach into the 8th Street Canal from the wetland is expected to be in the organic form and therefore unavailable to plants. • The significant reduction of average TKN values from Sample Point B to Sample Point E indicates dilution of TKN by downstream water inputs, or else a significant amount of the TKN present is in the form of ammonia nitrogen and is being removed by plants, or both. • If there is insignificant dilution occurring downstream of Sample Point B, then ammonia nitrogen is present. This means that a significant amount of the TKN at Sample Point B is comprised of ammonia nitrogen, and its source must be other than the wetland system, and therefore possibly emanating from properties on the north side of 8th Street. Such sources may include septic seepage, artesian well flow, irrigation runoff, and/or legacy loads. 7 FAPublic WorksWeithM\Stormwater Projects\IRFWCD 8th Street Canal Water Study\Memo 2 - 8th Street Canal.doc 38