One of the problems in a reverse osmosis process for livestock wastewater treatment is disposal of the by-product concentrate. The agricultural recycling of the concentrate is more cost saving than a further treatment. Application of the concentrate reduces the chemical fertilizer amendment. The agricultural recycling of the concentrate from the Kimhae livestock wastewater treatment plant, processed with the VSEP RO and bio-ceramic SBR, was studied. The concentrate includes non-biodegradable humic substance and residual inorganic ions (NH4+, NO3-, PO43-, K+, etc.). The contents of N, P and K were 1,650, 382 and 2,059 mg L-1, respectively. The total acidity of humic acids extracted from the concentrate was 5.17 cmol(+) g-1, composed of 2.38 cmol(+) g-1 of carboxylic group and 2.79 cmol(+) g-1 of phenolic hydroxyl group. Coliforms and E. coli were not detected in the concentrate. The yield of rice plant with the concentrate applied to it resulted in similar production to that with chemical fertilizer applied. The water extractable nitrate content of the concentrate-applied land did not exceed that of chemical fertilizer applied, at soil depths of 30 and 60 cm. The percolated amount of nitrate into the water table in arable land with the concentrate applied showed a similar level to that treated with the chemical fertilizer.

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