Experiments in Wastewater Polishing in Constructed Tidal Marshes: Does It Work? Are the Results Predictable?

Natural tidal salt marshes may have limited use in wastewater treatment applications. This chapter investigates salt marsh “polishing” of effluent from activated sludge treatment of clam processing waste to meet state regulations for BOD₅ and total suspended solids (TSS) and anticipated standards for N and P. In this chapter, three environmental factors are addressed using experimental results: Does tidal flooding frequency, which shortens wastewater residence to a few hours, prevent effective treatment? Natural salt marshes can demonstrate either net import or export of organic material and nutrients to surrounding waters. Is the behavior of pristine marshes a good indicator of their ability to polish wastewater? Is the outcome of polishing readily predictable in a variable natural marsh? Data from experiments are presented to answer these questions. With the exception of TSS, behavior of all parameters was moderately predictable for the warm season, but available winter data did not fit the same regression lines.