Nitrogen removal in its various chemical forms was evaluated in a complex of waste stabilisation ponds comprising ponds of different depths and geometries. TKN and ammonia removal reached 78.5% and >90%, respectively, in the 5-pond systems with overall retention times of only 19 days. Removals were highest in the maturation ponds, and shallow maturation ponds were the most efficient. In terms of optimum pond geometry, high nitrogen and ammonia removal was compatible with optimal BOD5 removal and faecal coliform die-off. TKN and ammonia removal in these ponds could be modelled using conventional first-order equations.

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