Use of Forests and Trees for Waste Treatment and Site Remediation: Reconciling Design with Research.

Slow rate irrigation of municipal and industrial wastewaters to natural and plantation forests has been a prominent  method of treatment for almost 40 years. The US EPA Process Design Manual For Land Treatment of Municipal Wastewater published in 1981, which was widely adopted by state agencies, has been the basis for almost all system designs. Many of the criteria established in this original design manual have remained unchanged and continue to be used for system design as represented in the updated Design Manual published in 2006. Research on operational systems shows fundamental differences between design and actual system functioning may exist but this research has been limited and there is a need for increased efforts to assess long-term system performance. More recently, use of forest plantations for phytoremediation of contaminated sites has become an important component of site remediation designs and often incorporate design features not always considered in land treatment design, particularly those land treatment designs utilizing natural vegetation systems.  Too often these designs fail to recognize how fundamental tree root-soil interactions will control phytoremediation success requiring a different level of design, functioning, and performance criteria.