State of the Technology On-site wastewater treatment (OWTS) ‘ Harold W. Walker, Ph.D., P.E. NYS Center for Clean Water Technology Josefin Hirst, P.E. and Stephen Cluff, P.E. Hazen and Sawyer 1 Objectives • Provide an overview of existing technology options for nitrogen removal from on-site systems • Identify knowledge gaps and opportunities • Rank technology to prioritize R&D efforts ‘ • Summary of CCWT efforts Methodology • Reviewed manufacturer information, research literature, past technology reviews • Met with practitioners, ‘ researchers in the field, other stakeholders • Engaged Hazen and Sawyer to compile existing information and develop a technology assessment 3 Conventional OWTS in Suffolk County • Basic treatment for single-family homes (1972 standards) consist of septic tank and precast leaching pools ‘ Source: http://104cliffroadeast.com/?page_id=955 Innovative/Advanced OWTS ‘ Source: http://104cliffroadeast.com/?page_id=955 Onsite nitrogen reduction technologies Onsite Nitrogen Reduction Technologies Classification Source Physical / Chemical Soil, Plant And Separation Biological Wetland Processes Processes Processes Urine Soil Treatment Recovery Membrane ‘ Unit Modification Separation Single Sludge BNR Wastestream Segregation Vegetative Ion Exchange Uptake / Two Sludge, Two Evapo- Stage BNR Transpiration Evaporation Constructed Wetlands Single Sludge BNR: single reactor carries out nitrification & denitrification Process: Cons: Pros: Suspended growth or fixed film More complex Relatively simple utilizing aeration process for operation installation nitrification and possibly Higher energy use nitrified effluent recycle for denitrification using WW carbon ‘ Two sludge, two-stage BNR Process: Two separate bacteria populations for nitrification and denitrification, requires electron donor from external source for ‘ denitrification Pros: Cons: Performance Capital costs Reliability Footprint Lower energy use Experience Biological process summary Single Sludge Single Sludge with Two Sludge, Process Sequential BNR Preanoxic Nitrified Two-Stage BNR Effluent Recycle BNR Electron Organic carbon from Organic carbon from External electron donor (Organic Donor bacterial cells influent wastewater carbon; Lignocellulose; Sulfur; Iron, Other) Typical N Reductions 40 to 65% 45 to 75% 70 – 96% • Extended aeration • Extended aeration Nitrification followed by: • Pulse aeration with recycle back to ‘ • • Porous media septic tank Heterotrophic Typical biofilters • Recirculating media suspended growth denite • Technologies • Sequencing batch biofilters with recycle Heterotrophic porous media reactors back to septic tank fixed film denite • • • Membrane Moving bed Autotrophic porous media fixed bioreactor bioreactor film denite • Norweco Hydro- Phase I - • Norweco Singulair Kinetic • CCWT pilot at MASSTC Suffolk Co. TNT • Hydro-Action Demo • CCWT Phase II Suffolk County Program • Busse • AdvanTex AX 20 and Demo Program AX-RT Future possibility, deammonification process - 1/2 mol Nitrite (NO2 -N) nitritation Anaerobic 37.5% O2 ammonia oxidation 1/2 mol Nitrogen gas (N2) 1 mol Ammonia (NH3-N) & Small amount of Nitrate Process: Conversion of ~50% of the ‘ influent ammonia into nitrite by ammonia oxidizing bacteria using nitritation, followed by the simultaneous removal of ammonia and nitrite by Source: Hazen (2016) anammox bacteria Cons: Pros: No OWTS experience Lower energy use Performance reliability Soil, plant and wetland processes Soil, Plant and Wetland Processes Vegetative Soil Treatment and Constructed Uptake / Infiltration Wetlands Evapotranspiration ‘ Heterotrophic / Free Autotrophic Surface Nitrification / Denitrification Submerged Anammox Soil, plant and wetland processes - soil treatment unit (STU) Process: Utilize physical, chemical and biological processes that occur naturally in the soil and/or plant ‘ Pros: Cons: OWTS Experience Performance Simple operation Footprint Lower energy use Nitrogen removing biofilter (NRB) ‘ Process: Pros: Engineered media layers for Performance Cons: nitrification and Footprint Experience denitrification using external Simple operation Construction complexity source for electron donor Lower energy Constructed wetlands ‘ Source: Kadlec and Knight (1996) Process: Engineered wetlands typically consist of Cons: submerged rock bed planted Pros: Footprint with wetland vegetation. Lower energy use Performance Providing aeration typically Mechanical reliability Capital costs increases TN removal. Construction complexity Physical/chemical processes Physical / Chemical Nitrogen Reduction Processes Membrane Ion Exchange Evaporation Separation ‘ Cation Exchange Examples: Incineration Reverse Osmosis (Ammonium) Nano Filtration Anion Exchange Solar (Nitrate) Distillation Membrane bioreactors Process: Integration of a permeable membrane material to facilitate solid-liquid separation and ‘ potentially support biofilm growth. http://www.lenntech.com/ Cons: Pros: Fouling Versatile High energy use Small footprint Membrane cost Microbial fuel cells Process: Application of an electrical potential between two electrodes causes an electric current to pass through the solution, which in turn ‘ causes a migration of cations toward the negative electrode and a migration of anions toward the positive electrode. Ionic components are separated Source: Lu et al. (2015) through the use of semipermeable ion-selective membranes. Cons: No OWTS experience High energy use Source separation Source Separation Wastestream Urine Recovery Segregation Greywater Black Water ‘ Phys, Chem, or Bio. Composting Treatment Irrigation Disinfection Incineration Holding Tank / Hauling Toilet Flushing Offsite Urine separating toilets Source: http://richearthinstitute.org Source: www.no-mixtoilets.com ‘ Source: http://richearthinstitute.org Source: www.treehugger.com) Source: http://richearthinstitute.org Source: http://richearthinstitute.org Source: www.wateronline.com Domestic Wastewater: Domestic Wastewater: Volumetric Flow Nitrogen Load Urine = Urine = 1% 75% Direct Application Precipitation Sorption & Ion Exchange Aeration/Stripping Stripping Urine Air Unit Air, ammonia ‘ Sulfuric Absorber acid Unit Air, ammonium sulfate Source: http://richearthinstitute.org Source: www.sswm.info Source: https://dspace.library.colostate.edu Nitrification & Electrolysis & Membrane Filtration Distillation Microbial Fuel Cells NO3 NO2 NH3 + NH4 Urea Source: www.eawag.ch Source: www.rsc.org Urine disposal options Treated to create Transport to WWTP Direct Land Application fertilizer/soil amendment ‘ Source: www.npr.org Source: www.mdpi.com Nitrogen Reduction Technology Ranking Assessment • A simple numerical ranking system was developed to prioritize available nitrogen reduction systems based on twelve selected criteria Effluent nitrogen concentration Restoration of performance Performance consistency Operation complexity‘ Construction cost Energy requirement CBOD/TSS effluent concentration Construction complexity Mechanical reliability Local resources Land area required Climate resiliency • A weighting factor was applied to each criterion based on the results of a Technology Weighting Factor Workshop Nitrogen reduction biological technology ranking summary • Top ranked single sludge BNR = rotating biological contactor Effluent Dispersal Septic tank ‘ Source: www.klar-environnement.com • Top ranked two sludge, two-stage BNR Nitrogen reduction soil, plant and wetland processes technology ranking summary • Top ranked = nitrogen removing biofilter (NRB) ‘ Urine source separation approaches ranking summary ‘ Source: www.npr.org Direct land application Source: www.no-mixtoilets.com Source: http://richearthinstitute.org Transport to WWTF Natural Biological Physical/ Source Systems Chemical Separation Promising Passive NRBs Two sludge, two- Membrane Urine recovery systems stage BNR bioreactor technology Opportunities • low cost • Effective • novel • resource • effective • media materials recovery • PRBs and replacement • resource wetlands • novel recovery pathways • Novel‘ pathways Knowledge • media • media • fouling • public gaps longevity, longevity • longevity acceptance replacement • PPCPs • nitrogen • beneficial use • design • design removal • PPCPs • PPCPs CCWT efforts • white paper • white paper • cellulose • Planning • pilot-testing • pilot-testing MBR stage • design • design • novel guidance guidance materials 26.