This study is focused on the diversity of bacterial communities from two series of horizontal subsurface flow constructed wetlands (CW) polishing high salinity tannery wastewater. Each series was planted with Arundo donax or Sarcocornia sp. in a substrate composed by expanded clay and sand. Chemical and biochemical oxygen demand removal efficiencies were similar in each series, varying between 58 and 67% (inlet COD 218 ± 28 mg L(-1)) and 60 and 77% (inlet BOD(5) 37 ± 6 mg L(-1)), respectively. High numbers of culturable bacteria were obtained from substrate and root samples - 5.75 × 10(6)-3.95 × 10(8) CFU g(-1) recovered on marine agar and 1.72 × 10(7)-8.46 × 10(8) CFU g(-1) on nutrient agar. Fifty bacterial isolates were retrieved from the CW, related phylogenetically to Firmicutes, Actinobacteria, Bacteroidetes, α-, β-, and γ-Proteobacteria. Changes in the bacterial communities, from roots and substrate of each series, related to the plant species, hydraulic loading rates and along CW operation were examined using denaturating gradient gel electrophoresis (DGGE). The clustering analysis suggested that a diverse and distinct bacterial community inhabits each series, which was related to the type of plant present in each CW.

Anaerobic digestion of olive mill wastewater (OMW) in admixture with anaerobically digested piggery effluent (ADPE) was investigated. Successive volumetric increases of OMW ranging from 8 to 91% were mixed with ADPE and treated through an upflow anaerobic filter to promote gradual adaptation of the microbial consortium. The response of the digester was positive, and only at 91% v/v OMW was lower reactor performance obtained, suggesting that a concentration on the order of 83% v/v was the highest in terms of the efficiency and stability of the reactor. At this inlet composition, the mixture loading rate varied from 5.0 to 5.7 kg chemical oxygen demand (COD)/m3·d and the total COD removal was 73 to 75%, with a gas production of 1.7 to 2.1 m3/m3·d (66 to 68% CH4). The corresponding volume of ADPE (17%) was enough to maintain an influent ammonium‐nitrogen (NH4+‐N) concentration of 0.17 to 0.19 kg NH4+‐N/m3 which was practically spent.

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