Nitrogen Removal Strategy

Design of a Modified Ludzack-Ettinger Process for Clark Water Corporation’s Wastewater Treatment Plant

Abstract

Clark Water Corporation (CWC) is the private sector concessionaire of the Clark Development Corporation (CDC) for the Clark Freeport Zone (CFZ). The company provides water and wastewater services to various industrial, commercial and residential customers inside the Freeport. One of the conditions specified in the concession contract is (Under Clause 9.1) [1]; “the Company shall ensure that from the Commencement Date until the expiry of the Concession Period the Facilities are at all times operated and maintained in accordance with: (a)     Applicable Laws;” Among the applicable laws that CWC needs to comply is the DENR DAO 2016-08 – Water Quality Guidelines and General Effluent Standards (GES) superseding the previous DAO 1990-35 imposing stringent values on the removal of Nutrients in the effluent discharge. CWC’s existing wastewater treatment plant (WWTP) is not adequately designed for this. The need to reduce ammonia is a new requirement and require a more sophisticated process. The paper focused on the process conversion of the current WWTP into a Modified Ludzack-Ettinger (MLE) process to meet the standards set forth in the revised DAO. Activated Sludge (ASPonds) will be converted into MLE which consist of an anoxic tank followed by an aeration tank and an internal sludge recycling system. The complete nitrogen cycle shall happen in the retrofitted ASponds. Nitrification will occur in the aeration tank while the nitrate produced will be recycled back to the anoxic tank. The design will involve the two (2) major components: process design configurations (volume projections, influent characterization & computation for air requirements) and the design of mechanical systems. Formulas & computations were encoded in Microsoft excel and its goal seek function was utilized to calculate the plant’s optimum design.  Though the paper made use of scientific set of calculations, many assumptions were made and formed the basis of the design.