Entry of waste water in the environment in the west is usually via sewage treatment plants. Determining the relative contribution of antibiotic concentrations and transfer of resistance is difficult as they have a common source. The overall effect of the treatment plants is complex and dependent on plant design and operation. One study of a plant with and without ozonation tertiary treatment showed that ozonation reduced antibiotics in effluents and downstream sediment to non-detectable levels, but the presence of resistant genes in downstream sediment was not affected.
Another inputs of antibiotics into the environment includes farming. In locations such as India or China, discharge from antibiotic production plants is important. High concentrations are found in surface, ground and drinking water and wildlife. India has produced a national action plan which includes setting antibiotic discharge limits from industry, farms, healthcare and veterinary care but is the only country so far to do so. This is also a recommendation in the recent O’Neil UK report.