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<br />e <br /> <br />e <br /> <br />Task 5 - Develop and Evaluate Alternatives <br /> <br />Based on the fmdings of Tasks 1 through 4, CDM will develop alternatives for improvements to <br />the sludge handling facilities existing and proposed regulations (Chapters 317 and 217, <br />respectively) at the Little Cedar Bayou WWTP. The alternatives will focus on improvements to <br />the sludge handling facilities in the following areas: <br /> <br />A. Sludge Digesters: The Little Cedar Bayou WWTP has inadequate aerobic digester <br />capacity. Without proper digestion, pathogen destruction can be incomplete and sludge <br />dewatering can be more difficult. A main focus of the evaluation and alternatives <br />development will be toward solving this problem including provisions to comply with the <br />proposed Chapter 217 regulations for aerobic digestion. The following solutions will be <br />evaluated: 1) adding additional digester capacity, 2) adding a pre-thickening step <br />preceding aerobic digestion to increase the solids concentration in the sludge, thereby <br />decreasing the volume of sludge fed to the digesters, or 3) a combination of additional <br />digester capacity and pre-thickening. It is not anticipated that alternative methods of <br />stabilization will be evaluated. However, a brief review of those alternatives will be <br />discussed with the City. Alternative methods may be warranted if the method of sludge <br />disposal is to be modified in the future (Le. sludge reuse or land application). In addition <br />to digester capacity issues, an evaluation of the blowers, air piping and diffusers will be <br />performed. Based on the condition ofthe existing equipment/facilities, recommendations <br />will be made for rehabilitation or replacement. In particular, efficiency improvements <br />will be recommended that could reduce operational costs. <br /> <br />B. Sludge Thickening: The use of the existing gravity sludge thickener will be evaluated. <br />_ Its viability in the sludge handling scheme will be re.viewed and recommendations will be <br />made. Factored in to the continued use of the thickener will be the reliability ofthe <br />sludge collection mechanism and the costs associated with maintaining that equipment: <br /> <br />C. Sludge Dewatering Process: The overall sludge dewatering process will be evaluated, <br />including polymer feed, sludge feed and dewatering. The dewatering process will be <br />evaluated as a complete process, but individual components will be evaluated as a part of <br />that process. Alternatives will be developed for improvements to the process with the <br />focus being on providing a system that is reliable, is simple to operate, provides adequate <br />redundancy, and is easy to maintain. Alternatives evaluated for the sludge dewatering <br />process will include: 1) rehabilitation or replacement of sludge conditioning and <br />dewatering equipment within the existing sludge handling building, 2) modification or <br />enlargement of the existing sludge dewatering building and rehabilitation or replacement <br />of equipment within that building, or 3) construction of a new sludge dewatering . <br />building. Due to the constraints within the existing sludge dewatering building, it is <br />anticipated that the study will focus on a new sludge dewatering facility. However, <br />investigation of all alternatives will be performed to ensure the best comprehensive <br />solution. <br /> <br />W:\LaPorte\sludge.SCO.doc 5/11/00 drh <br /> <br />Page 3 of 5 <br />