A one-dimensional, steady-state, dissolved-oxygen model and waste-load assimilation study for Wabash River, Huntington County, Indiana

The Indiana State Board of Health is developing a State water-quality management plan that includes establishing limits for wastewater effluents discharged into Indiana streams. A digital model calibrated to conditions in the Wabash River in Huntington County, Ind., was used to predict alternatives for future waste loadings that would be compatible with Indiana stream water-quality standards defined for two critical hydrologic conditions, summer and winter low flows.

The major point-source waste load affecting the Wabash River in Huntington County is the Huntington wastewater-treatment facility.

The most significant factor potentially affecting the dissolved-oxygen concentration during summer low flows is nitrification. However, nitrification should not be a limiting factor on the allowable nitrogenous and carbonaceous waste loads for the Huntington wastewater-treatment facility during summer low flows if the ammonia-nitrogen toxicity standard for Indiana streams is met.

This wasteload assimilation study is not based on a verified model. The changes in stream water quality predicted by the model represent only possible stream response to different effluent conditions.

The dissolved-oxygen standard for Indiana streams, an average of 5.0 milligrams per liter, should be met during summer and winter Zow flows if the National Pollution Discharge Elimination System's 5-day, carbonaceous biochemical-oxygen demands of a monthly average concentration of 30 milligrams per liter and a maximum weekly average of 45 milligrams per liter are not exceeded.