POLYMER TYPE AND ALUMINUM CHLORIDE AFFECT SCREENED SOLIDS AND PHOSPHORUS REMOVAL FROM LIQUID DAIRY MANURE

Abstract

Solids removal in flushed dairy systems by mechanical solid separators is about 20% efficient, resulting in severalmanagement problems. Due to the daily solids influx into the lagoon, storage capacity is continually reduced and frequentpumping is required to maintain capacity. Since the liquid portion of the waste is consistently applied to the same areas, soiltest phosphorus (P) levels rapidly increase above crop needs, thus increasing the environmental risk of P loss in the runoff.A more sustainable system must be developed that dramatically reduces the solids and P content in liquid manure prior toreaching the lagoon. This project evaluated the effectiveness of different polyacrylamides (PAMs or polymers) and aluminum(Al), alone and in combination, for removing solids and P from liquid dairy manure.<br><br>The eight different PAMs evaluated ranged in charge (-, 0, and +) and charge density (high, medium, and low). After testingthe PAMs alone and in comparison to the control, the cationic (+) PAMs significantly increased solids removal by almost twotimes and reduced the amount of total P (TP) in the filtrate by one quarter. The addition of Al in combination with both anionic(-) and cationic (+) PAMs increased removal of both solids and TP; however, the concentration range over which the cationicPAMs exhibited an increase in solids and TP removal was wider and more consistent than the anionic PAMs. Combinationsof Al and PAM decreased the TP retained in the filtrate by as much as three times when compared to the control. Treatmentconcentrations of Al was the only factor affecting the amount of soluble reactive P (SRP) retained in the filtrate with sometreatments producing <5% retention.