Considero que los links suministrados por Surender y Bachir son muy buenas guías para vuestra investigación. Disculpa escribirte en español, me siento más cómodo para expresarme.
It depends what you mean by standard. If you mean ISO standard (International STandert organisation, there isn't.
If you mean what are wastewater made of, there is quite an interesting overview in the web site and in various books (by private contact please). The key aspect is the wide range of concentrations, flowrates and so on from one country to another one could you precise your context?