One of the responsibilities that comes with proper operation of any wastewater system is the management and disposal of sludge, an unavoidable byproduct of the treatment system. Sludge management and disposal is highly regulated by the United States Environmental Protection Agency (USEPA) which has developed standards consisting of general requirements, pollutant limits, management practices and operations.
Whereas landfill disposal is certainly an option, for most communities, it is not ideal due to cost. Landfill disposal also eliminates the opportunity to repurpose the sludge, which contains nitrogen and other nutrients that make it a valuable commodity.
One beneficial way to dispose of sludge is to repurpose it as fertilizer/soil treatment for farm fields, or to process the sludge to a “Class A” certification, thereby allowing it to be sold as commercial fertilizer. When applied directly to fields sludge works especially well as fertilizer for crops such as corn and hay due to the nitrogen content. In areas of close proximity to rural farm fields, such as in the Midwest, the cost of fuel and hauling is more manageable, making direct application an affordable option for smaller communities. In most cases, farmers receive the treatment by-product with no costs for application, while the communities and operators are spared the cost of disposal fees. The process therefore proves beneficial for both parties.
Operators who have developed such arrangements with local farmers throughout the market are regulated by federal regulations which require diligent reporting with the USEPA. Reports are comprehensive and address aspects such as the application site, quantity of sludge spread, application site water specifications, slopes of application ground, accurate testing to ensure elimination of pathogens and much more. These regulations ensure the safety and integrity of the crops being grown as well as the safety of the community.
Disposal of sludge on farmland is the best practice for many of the communities that Alliance Water Resources partners with because of these benefits. Land application styles consist of liquid or semi-cake products. For smaller communities, with flows of less than two million gallons of water per day, a well-run plant will spend approximately 30-35 days each year hauling and spreading sludge, depending on the application style. Larger plants, typically located in more urban areas, may not be as well suited for this practice, as they produce greater volumes of sludge requiring disposal and typically require longer hauls to available farmlands.
When utilizing a fertilizer/farmland disposal process, it is important to note that Mother Nature plays a critical role, as does the growing cycle for each particular crop. Operators must time the application appropriately in the windows available.
Spring rains often dictate times when the ground is dry enough to allow the operation of heavy equipment used during application. The stages of crop growth must be accounted for when planning for fertilization. For example, application to hay crops must be made before the crops reach a certain height to avoid detrimental consequences to the product.
In the summer, the proper window falls after the first crop of hay is cut and before the grass reaches a certain height prior to a second/third cutting. Application cannot take place as hay crops are growing and maturing. After the last hay crop harvest, fertilization can be applied typically until the grass begins to go dormant. This timing works well in that it allows the sludge to work the ground throughout the winter.
After the fall row crop harvest, application can occur once the farmer begins working the ground. With proper planning, most farmers can lengthen the time period from harvest to ground work to allow for application.
In the winter, the window to apply bio-solids is greatly reduced due to weather conditions not being conducive for heavy equipment to be used on the fields. Also, regulations forbid application on frozen grounds when proper absorption would be questionable.
Of course, even with the best planning, Mother Nature can warrant the need for a Plan B. Operators must take into consideration possible weather obstacles during each season and incorporate alternative plans as they continue to operate their wastewater plants. This includes assuring they have enough storage available during times when hauling and applying will simply not be feasible.
Regardless of the process utilized, a good partner will take into consideration all aspects of a particular community’s resources in order to develop a system that is financially responsible for the long-term. This includes capital planning for technologies that can reduce cost over time, as well as forethought to how the growth of communities will warrant changes in needs.
For more information about sludge management or other questions about proper wastewater operations, contact Alliance Water Resources.