Nutrient and Suspended Sediment Mitigation Through the Use of a Vegetated Ditch System Fitted with Consecutive Low-grade Weirs

Author(s): Flora, C.; Kröger, R.

Mississippi is the largest producer of channel catfish (Ictalurus punctatus) in the United States. Channel catfish ponds cover over 20,000 hectares of land, mainly concentrated in the Alluvial Valley of northwest Mississippi. Water management practices to reduce mass discharge from ponds are currently a major point of concern, especially in light of potential regulations through nutrient criteria development. A vegetated ditch fitted with consecutive low-grade weirs is anticipated to be a practical and effective option of reducing nutrients and suspended solids entering downstream receiving systems. This study assesses the effect of low-grade weirs on chemical retention and settling of aquaculture pond effluent in a single drainage ditch. Nine embankment ponds were discharged at 48 hour intervals into a single vegetated drainage ditch fitted with 3 low-grade weirs. Two additional embankment ponds were discharged into the ditch while boards were removed from weirs, thus acting as a conventional ditch. Data were analyzed to quantify the ability of the low-grade weir system to reduce the levels of ammonia, nitrate, nitrite, total inorganic phosphorus, particulate phosphorus, and dissolved inorganic phosphorus. The levels of total suspended solids and volatile suspended solids will be compared across the system. As water passes each weir the nutrient and suspended solid loads should decrease through the system, overall reducing the load entering the downstream receiving systems.

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