By Dusty Sonnenberg, CCA, Ohio Field Leader: a project of the Ohio Soybean Council and soybean checkoff
Ever since the harmful algal bloom (HAB) of 2014 developed in the Maumee Bay of Western Lake Erie and impacted the water intake and treatment plant for the City of Toledo, the question of who is to blame has been center stage. Unfortunately, as multiple sources contributing phosphorus (P) have been identified, the blame game continued.
Agricultural run-off, industrial waste water, municipal waste water, and residential septic systems are the commonly identified sources of phosphorus entering the water. Many farmers feel like they have caught the most scrutiny because they are considered a non-point source compared to the industrial and municipal waste water sources, which are point sources. Municipalities will point to the strict regulations they must follow from the EPA for any application or discharge in comparison to agriculture.
Point sources typically have a single discharge point or multiple points that can be identified and monitored, whereas non-point sources cannot be measured as easily, and are typically a catch-all for what is left.
“We monitor the river water upstream and downstream from our discharge point, as well as test the actual discharge from our plant,” said David Pike, wastewater treatment plant supervisor for the City of Napoleon. “We know what the river water quality is before it gets here, and what it is after it leaves.”
One aspect of managing a wastewater treatment plant is the handling and disposal (or application) of biological solids (biosolids). Agricultural livestock production manages manure, and includes the way liquid and solid manure is stored and applied to fields. Municipal waste is similar. Wastewater from the city collection system is treated, with solids being separated, dewatered, and treated, then stored for application. Liquids being separated are treated before being discharged back into the river.
Under the H2Ohio program, farmers applying manure to fields in the Western Lake Erie Basin (WLB) are required to have a Comprehensive Nutrient Management Plant (CNMP) which outlines how the manure is collected, stored, and applied based on the agronomic needs of the crop rotation contained in the plan. For municipal wastewater treatment plants, the EPA requires a Biosolids Management Plan to be completed, which is a part of the National Pollutant Discharge Elimination System (NPDES) permit.
Similar to what is involved for manure storage on livestock farms, municipal waste treatment plants are required to have 180 days of storage for the biological solids (sludge) that they produce.
“We have to achieve a certain classification for our biosolids if we want to be able to apply them to fields,” Pike said. “There are three classifications. Class B, Class A, and Exceptional Quality. Class B (which is what a majority of wastewater treatment plants are) must be able to have their biosolids meet standards for pathogen reduction and vector attraction. Class A and Exceptional Quality classifications are similar, plus they are either thermo-dried, or lime stabilized.”
All three classifications of biosolids can be applied to farm fields. Managing the volume of the biosolid product to transport and apply is a challenge for municipal waste treatment plants, similar to what agricultural producers face with manure.
“Using lime to stabilize the biosolid product is relatively inexpensive, and does provide some additional value to the product as it has the lime component, however in that process you almost double the volume of biosolid to then be disposed of or applied later,” Pike said. “That additional volume creates additional cost.”
For farmers, the CNMP requires up to date soil test and information on crop rotations and yield goals in order to determine the agronomic rate of the manure to be applied. There are similarities for the Biosolid Management Plan.
“All fields must be approved for application based on a submitted soil test, the crop requirements and applications must be at an agronomic rate. The farmer must submit soil samples for the Biosolids Management Plan, and then we pull soil samples before we make the application to test metals, and closely monitor the P level,” Pike said. “Depending on the P level, the crop rotation and agronomic rate requirements the farmer has, determines the rate we can apply, and if we will make a one-year application, or if we can make a three-year application.
“The three-year application would meet the agronomic requirements for the crop rotation in that field for the next three years. For our product, that can be the difference of applying 1 ton per acre up to 3.5 tons per acre. The amount we are able to apply helps determine if it is cost effective for the city and farmer, to haul and apply to a specific field. We vary the rate based on the crop needs.”
One difference between agricultural manure application and municipal sludge field application is the notification of the public.
“Before we can land apply, the EPA requires that signs are posted in the field a week in advance. Those signs have necessary information that must be included, stating that the EPA has approved the field for Class B application of biosolids for a beneficial site, and those signs must remain in place for 30 days after the application is complete,” Pike said.
Fields with drainage tile also have specific requirements for biosolid application. All field tile and outlets must be monitored before, during and after the application, up until the biosolids are incorporated, or when the risk of discharge to waters of the state is no longer likely.
“We put tile stops in any field tiles that empty into the ditch prior to our application. Water control structures on outlets makes our job much easier, because we can just close them, and that takes care of it,” Pike said.
Setback distances are slightly different between agricultural manure and municipal biosolids. “We need to map out our isolations, because we need to stay 100 feet away from surface waters, 300 feet from an occupied structure or school, and 300 feet from any private, potable water source, and 1,000 feet away from a medical care facility,” Pike said.
Agricultural requirements are 300 foot setbacks from a sinkhole, public well, or public surface drinking water intake, 100 feet from a residence or private well, stream or ditch, and 35 feet from a stream or ditch with a vegetative buffer. Agricultural setbacks are reduced if manure is incorporated within 24 hours of application or direct injected.
“Most restrictions that prohibit biosolid application are the same as those for agriculture,” Pike said. “Biosolids cannot be applied to frozen or snow covered ground, or saturated soils, and in addition consideration is given to the soil classification based on the hydrologic group. For class B and exceptional use biosolids, no biosolids can be applied during a precipitation event, or if there is at least a 50% chance that a half inch of rain will occur within 24 hours of application, for hydrologic group A, B and C soils.”
That restriction is waived if the biosolids are injected, or if the biosolids are immediately incorporated and forecast does not indicate that there is at least a 50% chance that half-inch of rain will occur withing 6 hours after beneficial use.
For agriculture, manure cannot be surface applied when the local weather forecast for the application area contains greater than a 50% chance of precipitation exceeding a half inch in a 24-hour period.
There are also harvest restriction intervals for food crops, feed crops and fiber crops when they are grown if fields after the application of biosolids based on the nature of the crop.
When it comes down to protecting the environment and water quality, the treatment, handling, and application of biosolids, (and associated challenges), are really not that different from what livestock producers and crop farmers face with agricultural manure.