A biological process eliminates carbon, nitrogen and phosphor compounds from effluent water as it flows through a modified looped reactor which incorporates a further integrated looped pipe reactor. The novelty is that: (a) acids are formed in the integrated looped pipe reactor (63-66) in an anaerobic process and are mixed with the back-released phosphor compound in an anoxic process within the reactor; (b) this mixture is denitrified in a following stage upflow looped reactor; (c) the carbon compounds are oxidised and the ammonium nitrogen is nitrided in the downflow, while the residual carbon and ammonium nitrogen are oxidised and nitrated in the upflow; (d) the bacteria masses are concentrated with phosphor compounds in the two-stage aerobic process such that the resulting biogas may be released to the atmosphere. Further claimed is an appropriate assembly with a reactor chamber (1), a pipe reactor (16) with cascade (14), a looped reactor (18/19) with cascade separator (28), a loop reactor (6), a second reactor chamber (2), with slotted injectors (3), a looped reactor (63-66) with cascades (62/64, 65/67), cascade separators (28) and slotted injectors (4).
