Soluble phosphorus (P) removal by increasing swine manure pH was investigated in this study. Sodium hydroxide (1 M) was used to increase the manure pH from 6.5 to 9. Two aeration treatments (intermittent and continuous) were also used to raise the manure pHfrom 6.5 to 0 (for the intermittent treatment) and from 6.5 to 4 (for the continuous treatment) in a period of 15 days. An airflow rate of 1 L/minute was used for both schemes. Results showed that raising the pH to 8 by sodium hydroxide (NaOH) led to a reduction in soluble P concentration by 80. Increasing the pH above 8 had little effect on further removal of soluble P For both the intermittent and continuous aeration programs, the manure pH increased by about 1 unit within the first day of experiment, accompanied by a 75 reduction in soluble P concentration in the liquid. The treatment with continuous aeration did not show advantage over the intermittent mode in removing soluble P from liquid swine manure. Therefore, to accomplish the same level of soluble P removal, intermittent aeration should be recommended to save energy.
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