Analysis of 10 years of virus monitoring data from Los Angeles County treatment plants meeting California wastewater reclamation criteria

Six tertiary treatment water reclamation plants were monitored monthly for enteric viruses for 10 years. Secondary treatment removed 99.8% of the detectable viruses. The virus concentrator and assay system detected low levels of native viruses in 74 out of 75 unchlorinated secondary effluent samples. Only l of 590 final effluent samples averaging 1040 L (275 gal) was positive for enteric viruses. These results suggest that the California Title 22 treatment‐based water reclamation standards assure reliable production of essentially virus risk‐free effluents.