The LASA Biosolids Project includes the construction of the following:
- Two mesophilic anaerobic digesters with a total capacity of 2.2 million gallons, each with a diameter of 85 feet and a depth of 29 feet. They are designed to store 143,000 cubic feet of gas, and will include safety equipment including pressure/vacuum relief, flame arrestors, and flame traps and checks. Each digester will be mixed with 2 linear motion mixers, and will be heated by biogas, fuel oil, or heat recovered from the new dryer.
- One sludge dewatering centrifuge (to be in addition to one existing centrifuge). The centrifuge will handle up to 3,400 pounds of biosolids per hour at 340 gallons per minute at 2% solids, and will produce a minimum 22% cake.
- One sludge dryer. The dryer will use digester biogas as its primary fuel, consumed at about 16,676 cubic feet per hour, with fuel oil as a secondary fuel. The dryer will include a 9,400,000 BTU per hour boiler and will handle 10,000 pounds of wet sludge cake per hour at 22% solids, producing a minimum 90% solids product meeting Class A.
- One biosolids storage pad cover. The cover will be made from pre-fabricated metal with a 20 foot high translucent roof and clear span (no internal posts). The cover will be 32,912 square feet, or about 187 feet by 176 feet, and will provide three months storage at 2028 peak production rate.
- One Operations building and laboratory. The building will be 5,814 square feet, or about 102 feet by 57 feet, and will house plant operations staff facilities and a new laboratory. The new building will be constructed using LEED Silver practices. The current operations and laboratory building will be re-purposed into maintenance garage and shop areas and provide storage of spare parts and equipment.
Since 1997, LASA has undertaken 4 different studies (using 6 different consulting firms) to evaluate all aspects of stabilization, dewatering, storage and disposal. The 3 most recent studies recommended some form of anaerobic digestion, and 2 of these studies recommended heat drying. LASA carefully planned, studied and evaluated biosolids processing alternatives. In the end, we are confident our final selection of anaerobic digestion coupled with heat drying with biogas will provide a sound return on the Authority’s investment dollars and will result in a financially sustainable and environmentally friendly method of handling and distributing our biosolids product – making what was in the past a nuisance into a resource to be recovered and re-used. The project also meets two of the LASA Board’s strategic initiatives – to promote sustainability and encourage environmental stewardship.
This project will result in Class A biosolids that are more marketable, easier to dispose of, and pose less environmental risk, than the current Class B method. Although the current biosolids meets EPA standards, LASA is undertaking this upgrade as a voluntary, proactive way to reduce its environmental footprint and mitigate future risk. The project will result in Class A biosolids which is EPA’s highest standard.
LASA is currently evaluating how it will re-use its Class A dried biosolids. The most likely option will be to market the material on a wholesale basis to firms who provide such material to landscapers, farmers, and others for its organic content and nutrient/fertilizer value. Class A biosolids may be used as fertilizer on farms, parks, golf courses, vegetable gardens, and can be sold or given to home owners as compost or fertilizer.
Construction contracts were recently awarded for a total cost of $26.8 Million. Total project costs including all engineering and legal are approximately $28.3 Million. We do not expect this construction project to raise sewer rates beyond those rates currently projected in the LASA 5-year comprehensive plan. Total construction is estimated to take 18 months. Construction began in January 2016, and the system should be up and operating by June 2017.
Buchart Horn, Inc. provided the project design, and will provide construction management and resident inspection; Michael F. Ronca & Sons, Inc. is the General Contractor, Garden Spot Electric, Inc. is the Electrical Contractor, while Myco Mechanical, Inc. is the Mechanical Contractor.