Removal of human astroviruses from hospital wastewater by two biological treatment methods: natural oxidizing lagoons and rotating biodisks

Rotating biological disks and natural oxidizing lagoons are processes used to treat wastewater. These procedures were used in the present work and were situated in a pilot wastewater treatment plant situated in the residential area of Tunis City in Tunisia and received hospital wastewater from three nearby different clinics. This wastewater was very rich in various types of pathogens. Consequently, the monitoring of this treatment plant for hospital wastewater can be an appropriate approach to the study of the circulation of enteric viruses, such as human astroviruses. Wastewater samples (n = 102) were collected at the exit of the five basins from natural oxidizing lagoons and at the outlet of the rotating biodisks. Human astroviruses were identified in 55% (n = 56) of the wastewater samples by reverse transcription polymerase chain reaction (RT-PCR). An important increase was found in the frequencies of human astroviruses from the first to last lagoons of the natural oxidizing lagoon and at the exit of the rotating biological disks. Thus, these results showed the ineffectiveness of the two biological treatment methods studied for the human astroviruses removal. In addition, the data of this investigation pointed out the first detection of human astroviruses (genotype 1 and 6) in wastewater samples in Tunisia. These findings highlighted the inadequacy of the sanitary quality of treated wastewater for recycling, agricultural reuse and discharge into the receiving waters.