This paper discusses the evaluation, design and construction of two innovative treatment processes utilized as part of the expansion of the McCroskey Island WWTP to 8 MGD in Sevierville, TN – a lamella plate grit removal system and submerged effluent launders for secondary clarification. Lamella Plate Grit Removal System The WWTP has used an aerated grit and grease removal system since the mid-1990s that required routine repair and replacement of aging components. The aerated grit system was rated at a peak flow of 15 MGD. With peak flows in the expanded plant projected at 20 MGD, an expansion of the grit removal system was necessary. Several grit and grease removal treatment systems were evaluated, and a lamella grit/grease removal system was selected. The new 36 MGD lamella plate grit and grease removal system consists of an aerated and an unaerated grit trap chamber. In the first smaller chamber the wastewater is exposed to medium-bubble aeration. Floatable particles rise to the water surface where they accumulate and are removed by a paddle system just before the outlet. In the second unaerated chamber equipped with lamella units, the grit is removed axially by a horizontal screw conveyor. The grit-water mix is delivered by the grit pump into a grit washer compactor. This technology maximizes surface area for effective grit settlement. Submerged Effluent Launders The WWTP has two 80-foot diameter existing clarifiers. The units were constructed in the mid-1990s and equipped with inboard (floating) launders. During evaluation of the treatment plant, it was revealed that several of the existing supports have failed and that a portion of one of the clarifier launder floats. This causes short circuiting of flow in the clarifier. Repair or replacement of the existing launders was deemed too difficult to undertake given the plant’s heavy loading and limited ability to maintain compliance with only one clarifier in service. Submerged effluent launders were selected to replace the existing inboard launders. The self-supporting fiberglass reinforced plastic (FRP) submerged effluent launders are mounted on the inside of the concrete clarifier walls below the planned water surface elevation. Orifices in the launder, sized for the clarifier design flow, are evenly spaced around the clarifier perimeter to ensure even loading and minimize short circuiting. Flow is regulated by a level sensor in the clarifier and a PLC controlled a slide gate to maintain a constant water surface elevation as flow rates change. Two new 120-foot diameter clarifiers are in construction as part of the expansion of the WWTP. Submerged effluent launders offer similar benefits (replacing launder components) in new construction. In the case of new clarifiers, submerged launders offer the opportunity to avoid cast-in-place concrete launders and to build tanks with simpler vertical walls. Submerged effluent launders can provide an economical solution to replace aging or damaged existing launders and can be utilized in lieu of traditional launders, weirs, covers, and baffles in new construction. Both of these innovative treatment processes are among the first of their kind in use in Tennessee or Kentucky.