Biosolids Technical Bulletin

This bulletin is a "must have" for anyone involved in residuals and biosolids management. Whether you're interested in the latest treatment processes, odor management, beneficial use options, environmental management systems, or public outreach approaches, this publication has the information you need.

opportunity. The biogas is renewable, base-load, nonfossil energy. Using the digestate on land as biofertilizer completes nutrient cycles and conserves soil organic matter. Co-digestion with sludge protects the environment through 40 CFR 503 rules.

Existing sludge digesters can be “turbocharged” by retrofitting thermal hydrolysis, which enables the solids loading to be doubled or trebled, the specific biogas yield to be increased, and the digestate (which will be Class A) to be dewatered to cake that has approximately 50% greater dry solids content (34% dry solids, compared with 24%).

However, using FW in this manner, as digestate, is one of many options that utilities in the United States and worldwide must weigh. This article reviews the options for managing FW, their costs, and their environmental footprints.

Patrick D. Wootton

With treatment plants experiencing energy costs increasing by as much as 40% in recent years, new emphasis is being placed on energy efficiency. A valuable resource for energy production is digester gas provided by anaerobic digestion. The fact that only 20% of the wastewater treatment plants with installed anaerobic digesters and a flow rate greater than or equal to 18,925 m³/d (5 mgd) are currently utilizing their offgas for heat or electricity presents a relatively simple opportunity to offset energy costs.

Beyond the production of electricity and heat, the most significant issue for interested parties is how to treat the digester gas, specifically addressing concerns over the presence of volatile organic silicon compounds (VOSCs), also known as “siloxanes.” Siloxanes are detrimental to gas reciprocating engines, reducing engine efficiency, increasing emissions, and physically damaging engine parts and components. This article provides a background on siloxanes and their prevalence, investigates their effects on engine applications, and presents solutions to removing them from digester gas.

NEWS

Methane To Power Half of Milwaukee’s Wastewater and Biosolids Facilities

A $90 million methane piping project will reduce Milwaukee’s greenhouse gas emissions by 454,000 Mg/yr (500,000 ton/yr) and the city’s 454,000-m3/d (120-mgd) wastewater treatment facility’s emissions by 95%, according to a study by Brown & Caldwell (Walnut Creek, Calif.).

Milwaukee’s latest green initiative is projected to save the city and its ratepayers (about 1.1 million in a 28-community service area) $148 million over a 20-year period and will utilize waste methane — currently flared — from the active Emerald Park Landfill 27 km (17 mi) away in Muskego, Wis.

Orlando, Fla., Aims To Convert Biosolids Into ‘Green’ Energy

City will test innovative process that creates energy while eliminating the need to dispose of biosolids

For the past few years, the City of Orlando, Fla., has pursued a unique approach to handling wastewater solids. Relying heavily on the construction prowess of its wastewater treatment staff, Orlando has built a first-of-its-kind oxidation reactor at its Iron Bridge Regional Water Reclamation Facility. With pilot-testing set to begin in early 2010, the city may know soon whether its new approach to handling biosolids is feasible.

Technologies Target Digestion Process To Cut Solids, Boost Biogas Production

High energy, chemical, and solids disposal costs are spawning interest in virtually any technology that promises to ease these burdens for wastewater treatment plants (WWTPs). Two “new” technologies about to emerge in the U.S. wastewater market tackle this issue by enhancing the digestion process, yielding improved dewatering and less solids for disposal, proponents claim. Both technologies are already established, one at WWTPs in Europe, Australia, and Asia, and the other for applications in cooling-tower water treatment.