Morehead City Benefits from New Enhanced Biosolids Drying Technology

摘要

Morehead City Wastewater Treatment Plant (WWTP), located in Morehead City, North Carolina (NC) wanted to transform their solids handling plant into a high quality, Class A or Class B biosolids facility. Morehead City staff evaluated traditional drying, lime stabilization, and evaporation to further dewater digested belt-press cake effluent in terms of which process could offer the best value to the City in terms of their four-point decision matrix: energy, environment, flexibility, and economics. The City selected RDP’s Hybrid Evaporator? following the documented success of the mobile pilot unit at seven facilities in NC, Utah, Indiana, Florida, and Pennsylvania and due to its reduced energy usage, nutrient value, operational flexibility, and cost of operation. This is RDP's first full scale installation of this technology. Optimizing operation, demonstrating consistency of biosolids quality, and proving viability of biosolids is essential to the successful implementation of a diverse biosolids management plan (BMP). Determining process capabilities for a cost-effective new alternative to traditional drying, quantifying the nutrient value of produced biosolids, and using tissue sampling to confirm nutrient uptake by locally pertinent agriculture differentiates this Biosolids Application Demonstration Program (Program) from other BMPs. Starting in March 2011, a 12-month demonstration project was initiated to evaluate these project goals. This Program determined the production capacity of the full scale unit at 15 tons of wet cake at 15 to 20 percent solids per 8 hour day. Evaporation rates currently matches those of known direct dryers, however continued optimization is expected to show efficiencies more in line with other indirect drying technologies. Nutrient content analyses showed unparalleled stability, with an N:P:K of 2.5:3.5:0.3, comparable to Milorganite. Initial soil and tissue sampling showed improved soil conditions, crop yield, and nutrient uptake when using Morehead City biosolids when compared to use of standard fertilizers. Lastly this program was able to show a 25 to 35 percent operational cost savings in using this Class A option when compared to lime-stabilized Class B hauling options excluding any revenue from local users.