flush dairy – Livestock and Poultry Environmental Learning Community

Purpose

Manure lagoon systems are designed to hold and treat animal farm wastewater for a predetermined period and remain popular in many livestock farms. If the lagoon is properly designed and built, many years can go by without any significant maintenance requirements outside of water management, pumps and valves. Depending on the capacity and maintenance, additional manure solid removal is often required to reduce the amount of manure solids entering the lagoon storage. When excessive solids build-up or sludge was found, significant odor and low quality/quantity of flushing water would be the issues.

This study documents experience to prepare for and complete land application of lagoon effluent with heavy solids from a flush dairy lagoon in central Missouri. The free stall barn uses mattress bedding with supplemental cedar shavings and houses 140-160 lactating cows. Preparation included measuring lagoon sludge depth and lab analysis of sludge characteristics and scouting for crop fields for land application prior to contacting contractors for a bidding process. A contractor team utilized specialized equipment to dilute, agitate, pump and land apply approximately 8 million gallons of diluted lagoon solids in less than nine working days. Lagoon effluent was sampled throughout the process to monitor the mass of nutrients applied to specific plots of land. For effective lagoon solids removal and land application, proper preparation, specialty equipment and trained professional, timing of the crop fields, and adequate field working days are critical. Simple, non-mechanical technologies are available for even small to midsize dairy farms to reduce the cost of lagoon maintenance by preventing the bulk of solids from entering the lagoon.

What Did We Do?

We documented the process of lagoon solids removal for land application, considering the preparation (sludge and effluent sampling), specialty equipment and trained professionals, timing of the crop fields, and adequate field working days. The barn was flushed two to three times per day, with three times per day being typical. There was, at one time, an elevated screen that helped remove the large solids from the flush, but the screen system fell into disrepair several years ago and was abandoned. Solids in the lagoon were agitated and pumped out from May 21, 2020, through June 8, 2020, Figures 1 and 2. A total of 8 million gallons over 280 acres was applied to fields further away from the lagoon, including neighbor’s crop fields that were 1.5 miles away. Equipment needs and specifications were documented (Canter et al., 2021) and being prepared for an Extension publication.

Figure 1. PTO-drive lagoon agitators and agitation boat in operation.

Figure 2. A dilution pump was used to pump water from the nearby lake (left) to the dairy lagoon (right) with agitation boat and lagoon agitation working in the background.

Daily lagoon effluent samples were taken multiple samples throughout the day on June 2 to gauge the consistency of nutrient concentrations. Results suggest that once completely mixed via agitation, the applied nutrient concentration from a single sample is a reliable estimate within a working day if the moisture content is consistent. The initial slurry had a 10-13 percent solids content, so a significant amount of dilution water was needed to dilute the solids content to the target range. The exact amount of dilution water used was unknown. Figure 3 shows the concentration and moisture data. In general, the higher the moisture content (less solids) in the slurry samples, the higher the concentrations of the important manure nutrients are. The team evaluated potential technologies based on historical experience and first-person interviews. A pull-plug sediment basin (PPSB) was selected after reviewing cost and visiting with a farmer who operated a PPSB and was satisfied with the overall operation and performance (Canter et al., 2021). The application rate of important manure nutrients did show variation during the several days of land application, suggesting an improvement to the real-time effluent nutrient measurement and land application rate adjustment could be improved to provide more consistent nutrients to the crop fields.

Figure 3. Concentrations and moisture content of slurry samples from the lagoon.

What Have We Learned?

Manure management can be a burden for animal feeding operations, which can potentially become a significant threat to the profitability and management of farms if not proactively managed. Owners would be well-advised to survey their lagoon yearly to track solid inventory and plan ahead for the amount of land needed for solids application. Proper solids removal from the lagoon, particularly if regular and effective solids removal has been neglected, requires specialized equipment to reduce liquid supernatant on an annual or semiannual basis. There can be significant variability of nutrient concentration and resulting mass applied. Testing for nutrient concentrations in the lagoon, whether supernatant or sludge, or both, can be misleading due to variance in concentrations due to moisture content as the applicators dilute and concentrate the solids during the land application process.

Daily sampling during land application could help but may not be practical due to the analysis time generally required by labs (5-10 business days). Sensors and probes are available that return instantaneous values and have been used in municipal and industrial wastewater treatment for over a decade. Companies have offered integrated sensors for land application equipment, combining them with their GPS and flow control system to give a complete and accurate summary of nutrient application. Simple, non-mechanical technologies are available for even small to midsize dairy farms to reduce the cost of lagoon maintenance by preventing the bulk of non-degradable solids from entering the lagoon. Implementation of a coarse solids separation system such as the PPSB could significantly reduce the long-term cost of manure management by allowing the operator to use more common equipment (e.g., a loader and spreader) to remove solids from the manure management system.

Future Plans

Continuous monitoring of the lagoon sludge level at a minimum of annual basis is needed to closely monitor the lagoon solid accumulation and performance of the PPSB. The authors are collaborating with NRCS team to improve the PPSB and ways to monitor the lagoon sludge level.

Authors

Teng Lim, Extension Professor, Agricultural Systems Technology, University of Missouri

Corresponding author email address

Limt@missouri.edu

Additional authors

Timothy Canter, Extension Specialist, Agricultural Systems Technology, University of Missouri

Joseph Zulovich, Extension Assistant Professor, Agricultural Systems Technology, University of Missouri

Additional Information

1. Canter, T., Lim, T.-T., and J. A. Zulovich. 2021. Field Experience of Removing and Land Application of Dairy Lagoon Solids. In International Symposium on Animal Environment and Welfare. Rongchang, Chongqing, China.
2. Lim, T.-T. 2022. Lagoon Solids Removal, Lessons Learned. Cleanout for Lagoons and Anaerobic Digesters, Jan 21, 2022. Webinar of Livestock and Poultry Environmental Learning Community (LPELC). https://lpelc.org/cleanout-for-lagoons-and-anaerobic-digesters/
3. Canter, T., Lim, T.-T., Chockley, T. 2021. Considerations of Pull-Plug Sedimentation Basin for Dairy Manure Management. University of Missouri Extension Publication. Retrieved September 25, 2021. https://extension.missouri.edu/publications/eq302.

Acknowledgements

USDA NIFA, Water for Food Production Systems Program A9101, for supporting the project. It is titled “Management of Nutrients for Reuse”, a multi-faceted project that involves professionals from the University of Arkansas, University of Nebraska, Colorado School of Mines and Metallurgy, Case Western University, and University of Missouri.

Joe Harrison, Professor, Livestock Nutrient Management program, Washington State University

Gilbert Miito, Postdoctoral Fellow, Agricultural Systems Technology, University of Missouri

Richard Stowell, Biological Systems Engineering, University of Nebraska

Farm crew and custom applicator team for their help.

Purpose

Many small and mid-sized dairy farms use flush systems for manure removal due to reduced chore time and increased barn cleanliness. Often, flush systems require greater attention to onsite water management and frequent lagoon maintenance. While anaerobic lagoons provide some digestion of manure solids and sludge storage, solids removal may help increase lagoon capacity and reduce costly lagoon sludge removal. A pull-plug sedimentation basin (PPSB) is a passive solids removal system that can reduce the operational time and cost of the overall manure management system by acting as both a sedimentation basin and pre-lagoon solids filter system.

Larger, denser particles accumulate on the basin floor, while buoyant particles (e.g., undigested fiber, waste forage, bedding, etc.) form a floating mat on the surface. The mat acts as a natural filter and retains some of the solids from the waste stream. The PPSB was developed as part of a collaborative effort between USDA NRCS and small dairy producers in Missouri. This abstract provides background and basic information on the PPSB, while more performance evaluation of the system based on nutrient retention, costs, and maintenance and operational considerations can be found in a University of Missouri Extension publication Eq302 (Canter et al., 2021).

What Did We Do?

Design details of a working PPSB were documented, and performance evaluation was conducted based on grab samples of the flush and PPSB locations. Critical design considerations for the PPSB including design, hydraulic loading, location of the pull-plug location, and construction details were reported in the Extension publication (Canter et al., 2021). The concrete entry ramp into the PPSB should have a maximum slope of 12:1 (or 5 degrees) (Figure 1) to minimize wheel slippage and potential for equipment overturns. The example provided in Figure 1 is of a typical PPSB design that serves a herd of ~150 milking cows with a single-flush volume of ~7,000 gallons but also represents the smallest recommended size of the system. A minimum depth of 6 feet is needed to keep settling solids out of the discharge stream.

Figure 1. Profile and plan views of typical PPSB (dimensions in feet).

Detailed discussion of the advantages and disadvantages of the PPSB system was reported in the Extension publication. Relatively little maintenance has been reported, while the pull-plug is the only moving part and may need to be replaced if damaged during cleaning or degradation, Figures 2 and 3. Details such as the management and sampling and analysis were discussed, and a case study was conducted to document the information of a PPSB system of a 120-hd dairy farm in Missouri, with a flush system and sand lane, as well as a performance evaluation.

Figure 2. A PPSB system in operation at a dairy farm.

Figure 3. PPSB with liquid discharge pipe, after manure solid was removed.

What Have We Learned?

The owners are satisfied with the performance of the PPSB, which is considered a low-maintenance, low-technology option to efficiently manage manure solids within a flush system. The primary benefit of the PPSB is a reduction in time spent agitating and removing solids/sludge in the lagoon. When less capacity in the lagoon is used for solids treatment and storage, there is more room to store water and longer intervals between repairing or unclogging pumps and the water system. There are typically three to four clean-out periods per year, depending on PPSB and herd sizes and other factors.

The primary benefit of the PPSB is the removal of manure solids using a low maintenance system, resulting in longer intervals between lagoon agitation and land applications. Approximately 23,450 cubic feet of manure solids were prevented from entering the lagoon each year, along with 6,454 pounds of nitrogen (438 pounds as ammonia-nitrogen) and 2,415 pounds of phosphorous. These represent 13 percent and 28 percent of manure-based nitrogen and phosphorous, respectively, being retained in the PPSB.

Future Plans

Additional sampling just before or during clean-out is necessary for a more accurate performance determination. PPSB installed at larger dairy farms, and those using different bedding should be evaluated for performance and documented the cost savings as compared with other popular solid separation systems.

Authors

Teng Lim, Extension Professor, Agricultural Systems Technology, University of Missouri

Corresponding author email address

Limt@missouri.edu

Additional authors

Timothy Canter, Extension Specialist, Agricultural Systems Technology, University of Missouri

Troy Chockley, Environmental Engineer, Natural Resource Conservation Service, United States Department of Agriculture

Additional Information

Canter, T., T.-T. Lim, and T. Chockley. 2021. Considerations of pull-plug sedimentation basin for dairy manure management. University of Missouri Extension. https://extension.missouri.edu/eq302