Phosphorus Removal from Domestic Wastewater Using Engineered Nano-media

Dissolved, bioavailable phosphorus originating from onsite and municipal wastewater is being recognized as one of the contributors to eutrophication and, more recently, high profile cyanobacteria incidents. This has resulted in very low regulatory limits in some regions, well below 1 mg/L, which are very hard to economically and reliably reach with conventional biological and chemical treatment technologies. A new class of engineered nano-media containing a high porosity, high surface area iron substrate populated with nano-iron oxyhydroxide was tested on wastewater from 3 cluster onsite wastewater treatment systems and 4 municipal plants. Results show much potential to reduce phosphorus levels from 1 mg/L to below 0.3 mg/L using an empty bed contact time (EBCT) of 1 hour. Longer EBCTs result in a further decrease in effluent concentrations. A 0.10 L/min demonstration unit with an EBCT of 1.5 hours reduced influent phosphorus from 7.2 mg/L to 0.4 mg/L for over 60 days, with no sign of breakthrough. Long-term column testing indicates that the capacity of the media treating wastewater can be over 50 mg P/g media. The sorption mechanism is equilibrium based enabling the use of empty bed contact time as a design parameter. INTRODUCTION Phosphorus is often the limiting nutrient that controls eutrophication. Municipal wastewater treatment plants contribute approximately 5% of the environmental phosphorus loading and onsite wastewater is estimated to contribute 4 – 35% (Lombardo, 2006). However, phosphorus is also a valuable, scarce commodity that is produced from phosphate rock. Cordell et al., 2009, estimates that phosphate rock reserves are expected to be exhausted within 50 – 100 years. Phosphorus removal at large municipal wastewater treatment plants is typically achieved through biological and/or chemical mechanisms. Biological phosphorus removal requires multiple reduction/oxidation environments, an appropriate carbon to phosphorus ratio, and careful operation to avoid upsets (Neethling and Gu, 2005; Oehmen et al., 2007). Chemical phosphorus removal entails the addition of a metal salt to precipitate phosphorus followed by sedimentation and/or filtration. Both are inexpensive, especially biological, and very effective down to an effluent level of approximately 1 mg/L. However, neither technology is well suited for onsite wastewater applications which do not have daily maintenance or the routine removal of biosolids. Michigan State University, Department of Biosystems and Agricultural Engineering, East Lansing, MI 48824 MetaMateria Technologies, 870 Kaderly Road, Columbus, OH 43228 3 Consumers Energy Business Solutions, 3965 Okemos Road, Suite A1, Okemos, MI 48864 *Corresponding Author: [email protected]