Supercritical water oxidation (SCWO) technology for sludge and micropollutants treatment Kobe Nagar CEO, 374Water Inc. Lead Engineer Dept. of Civil and Environmental Engineering, Duke University GLOBAL SLUDGE PROBLEM COSTS SOCIETY $BB Wastewater Sludge in Wastewater Sludge Industrial Wastewater Developing Countries USA Sludge - USA Current treatment creates secondary pollution “10 million pounds of poop from New York are stranded in a rural Alabama rail yard” “Safe” storage and landfilling are not sustainable It never really goes away – we just move it around… CURRENT TREATMENT METHODS ARE LIMITED Climate Adaptable Technology Limited Treatment and excess use of non- biodegradable products ► Shifting of weather patterns around the world, causing shortages and ► GenX (PFAS), PAHs, pesticides, droughts in some areas and floods in pharmaceuticals, microplastics others. ► Nutrient pollution from land application ► By 2025, two-thirds of the world’s excess nitrogen and phosphorus population may face water shortages. https://www.worldwildlife.org/threats/water-scarcity “We can not solve our problems with the same thinking we used when we created them” - Albert Einstein Could SCWO be the alternative to sludge treatment? SCWO Process + + + >374 °C ~221 Bar Organic Air Clean Lower GHG Energy Waste Water Emissions Sustainable, decentralized & superior on-site treatment This barrel is an The same energy as in 87 kWh 3 gallons of worth of dump! gasoline 6 Giphy.com SUPERCRITICAL WATER SC Water has similar strength as Acetone to dissolve organic compounds Supercritical Water Oxidation (SCWO) Solution SCWO Process + + + + + >374 °C 250 Bar Electricity Organic Waste Air Heat SCWO converts organic waste into clean water, heat, electricity and CO2 in seconds! 8 BREAKTHROUGH TREATMENT TECHNOLOGY Very fast reaction (seconds) - small footprint Complete elimination of pathogens & micro-pollutants Energy-efficient and possibility for off-grid operation at scale No pollution, no odor The industrial-scale pilot unit on Duke campus can treat Can cotreat hazardous the fecal waste of ~1000 people per day industrial wastes (oil, chemical, pharma, etc.) Scalable and offer competitive cost to AD and other methods UN SUSTAINABLE DEVELOPMENT GOALS ADDRESSED Fecal slurry & septage A TRUE OMNI PROCESSOR Biosolids disposal Animal waste treatment Cost (ROM) = CapEx + OpEx Hazardous waste treatment Compact $$$ SCWO $$$$ Lime stabilization $$$ Anaerobic Incineration $$$$ $$$ Drying + digestion Polluting Clean 0* $$ Incineration Dumping Anaerobic ponds, $$$ Drying beds Landfilling Land application $$ $* $$ Composting Lagoon, Sprayfield Space Intensive * Not including lawsuits LOWER COST, ENERGY, AND FOOTPRINT Incineration Anaerobic Digestion SCWO Treatment (VSR) CapEx OpEx Plant Footprint Energy consumption Polluting emissions Sustainable 12 WHY SCWO? WHY NOW? Innovation • Mixing tee configuration - avoids fouling and limits corrosion • Integrated energy recovery system – enables the system to run off the grid and generate electricity at a large scale • Safety – using air (vs. pure oxygen) and having the ability to limit temperature and avoid runaway reaction Proven pilot plant • Pilot plant at Duke Campus operational since 2015 – demonstrating successful treatment various feedstocks and micro-pollutants Demand for sustainable solutions • Running off the grid • Flooding resilient • Future proofing regulations for micro-pollutants • Phase-out of Hearth Incinerators by 2025 Our Path to Date ► Operating & ► Running with ►Reliability testing safety procedures slurries prototype A ► Construction ► New reactor ► Commercial ► Commissioning design development 2014 2016 2018-19 2013 2015 2017 ► Reactor design ► Liquids treatment ► Energy recovery ► Electrical & ► Aspen Plus investigations control design modeling ► New slurry pump ► Procurement ► Slurry handling ► Prototype B design 14 A fully functional prototype – 1 ton per day (Nix1) 15 Inside our pilot, the Nix1 16 Inside Prototype A WASTE TYPES & CALORIFIC VALUE Dewatered Waste Primary secondary activated Food Waste sludge sludge sludge (WAS) Dry solids: 20-30% Dry solids: 13% Dry solids: 27% Dry solids: 30% Ash content: ~27% Ash content: 18% Ash content: ~35% Ash content: 6% Calorific value: Calorific value: Calorific value: Calorific value: 16.3 MJ/kg 13.9 MJ/kg 15.7 MJ/kgdry dry dry 16-19 MJ/kgdry We use the energy embedded in the waste to fuel the reaction no need to digest the waste first Typical Biosolids Treatment Performance Analysis Influent Effluent Removal % COD (mg/L) 214,000 70 99.97 Total N (mg/L) 10,875 200 98.2 NH3 (mg/L) 443 17.6 - NO3 (mg/L) 183 15.9 - NO2 (mg/L) 14.9 0.4 - -3 PO4 (mg/L) 4930 67.9 98.6 pH 6.8 7.02 - 19 SLUDGE TREATMENT – TYPICAL RESULTS WASTE ACTIVATED SLUDGE (WAS) SCWO EFFLUENT Pre-feed processing included diluting the feedstock ppm mg/l to 11.5% solids, macerating and adding co-fuel. To 70 26 reach a 180,000 mgO2/L COD, 11.5% COD Ammonia In Effluent In Effluent concentration – we added 0.05 kg of diesel and 0.44 kg of water to each kg of sludge. After reaching a smooth consistency, the slurry was fed to the SCWO reactor using a high pressure >99% 93.7% 95.6% pump. It was preheated to 200 ºC and reacted at supercritical conditions. VSR Nitrogen Phosphate Removal Removal Calorific value (0-20 kJ/ kg dry) COD (Chemical Oxygen Demand): high conversion of over 13.4 kJ/kg 99.9%, from 170,000ppm to 70ppm (effluent is clean water and inert minerals; after further filtration results improve even further). Ash content (0-40%) VSR (Volatile Solids Reduction): current technologies can reach a range of 16-40% of VSR. We reached >99% - a 34.8% standard SCWO capability. Ammonia, Nitrogen, Phosphorous: most of the nitrogen is converted to nitrogen gas. Total nitrogen in the effluent is Solids (0-30%) 90 mg/L, phosphate level in the dry mineral output stream is 17.4% ~10% mass as P2O5. 20 pH level in effluent: 6.6 Fate of N and P and S during treatment N Forms SCWO Exhaust • Organic Process Gas <3 ppm NH • Urea v 3 N gas <5 ppmv NOx • Ammonium 2 <3 ppmv SOx • Heterocycles P Forms Solid minerals • Organic Phosphate precipitates • Phosphate Ca3(PO4)2 S Forms MgNH4PO4·6H2O - • HS , COS, organic Sulfates, Hydrates • Mercaptans CaSO4 21 Treatment of Emerging Contaminants Experimental Approach • Spike trace contaminants to during IPA phase and to biosolids Results • Ibuprofen and acetaminophen: spiked 10 mg/L each Effluent: ND at < 1 µg/L Removal > 99.99% • Triclosan: spiked: 100 µg/L Effluent: ND at < 0.1 µg/L Removal > 99.9% • PFOS: spiked: 2-6 mg/L Effluent: 5-30 µg/L Removal 98.6-99.7% • PFOA: spiked: 2-7 mg/L Effluent: 0.1-0.4 µg/L Removal > 99.8% Emerging contaminants are well removed This reduces concerns for water reuse 22 SCWO PFAS (FOREVER CHEMICAL) TREATMENT We spiked a biosolids slurry with high concentrations of PFOS and PFOA before feeding it to the Supercritical Water Oxidation omni- 6.3 mg/l 7.3 mg/l processor Spiked biosolids Spiked biosolids slurry with PFOS slurry with PFOA SCWO EFFLUENT Effluent Analysis 6.000 > 99.7% > 99.9% 1.000 0.167 PFOS PFOA Removal Removal 0.028 0.005 Non-detect Concentration (µg/L) 4 mg/l (<0.2 ppmv) 0.001 Fluorides in liquid effluent, PFBA PFBS PFDA PFHpA PFHxA PFHxS PFNA PFOA PFOS PFPA HF (@vent) showing recovery of F ppb ng/l 0.079 0.000 0.010 0.142 0.069 0.004 0.000 0.120 5.336 0.070 atoms as F- Co-fuels and Other Wastes Co-treated with Biosolids Tested to date in our pilot • Isopropyl alcohol (IPA) • Diesel Typical removal • Waste motor oil, vegetable oil • COD: 99-99.9% • Landfill leachate • Total nitrogen: 50-98% • Food waste • Total phosphorous: 73-99% • Plastics waste (PET, PE) Lessons learned • Successful treatment • Quantified impacts e.g. on emissions • Broadens scope of SCWO application • Enables synergistic opportunities Adding waste cooking Mixing ground food oil to biosolids waste and scraps 24 OUR VISION – DECENTRALIZED ON-SITE TREATMENT Mixed waste streams Raw sludge & Biosolids Hazardous waste • Primary from pits or septic emptying Fecal sludge • Secondary sludge Animal waste (Digested or undigested) Other applications • Industrial WWTP • CAPOs Sludge • Military and Emergency responses Cluster of Buildings Communities on microgrid Example SCWO treatment Nix6 facility in 20 ft. container One 40 ft container treats for 1000-3000 people waste from 6,000 people Energy Minerals Distilled water CO2 (carbonation, capture) Energy Balances Nix1 Nix6 Nix30 Nix200 (prototype) (commercial) (commercial) (commercial) (not optimized for efficiency) 5.1 ton/day 25.5 ton/day 170 ton/day Losses 1 ton/day 20 kW 26 kW 10 kW 12.5 kW 167 kW 300 kWh/day 4000 kWh/day Cost - Distributed Treatment (community to city scale solutions) Power Distilled Total Capacity wet Estimated consumed water treatment metric ton /day Land use CapEx or produced costs (CAPEX (people*) ($/Unit) produced (ga/day) + OPEX) Nix6 One 40’ Consumes 5.1 wet ton/day ISO 700 $2M $144 per ton 10 kW Community container Nix30 Three 40’ Produces 25.5 wet ton/day ISO 3,600 $4.5M $55 per ton 12.5 kW Town Containers Nix200 Produces 170 wet ton/day ~5000 ft2 24,000 $17M $26 per ton 167 kW City Scale 27 IMPLEMENTATION (EXISTING WWTP) Feed Secondary Plant Discharge/ treatment Land Application Clarifier (Primary treatment) Sludge Water Brackish Water (Option for RO) (Dewatering) Filter & 10-15% slurry Dewatering mixed with FOG (option) to SCWO unit Minerals SCWO Distilled (Fertilizer) Water 28 OWASA (CHAPEL HILL) CASE STUDY Not in use / Two Nix 30 units extra capacity X X XX X X X X X X X X X Eliminate