Urine concentration by forward osmosis process

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osmosis process Takeru Maeda, Benedicte Carolle Nikiema, Guizani Mokhtar, Ryusei Ito, Naoyuki Funamizu

1 The 13 th IWA specialized conference on small water and wastewater systems The 5 th IWA specialized conference on resourcesoriented sanitation September 14 th ~16 th, 216 Urine concentration by forward osmosis process Takeru Maeda, Benedicte Carolle Nikiema, Guizani Mokhtar, Ryusei Ito, Naoyuki Funamizu Laboratory on Engineering for Sustainable Sanitation, Graduate school of Engineering, Hokkaido University, Japan

Introduction 2 N+P 2 O 5 +K 2 O [Mtons] 2 15 1 5 14 39 Global consumption of nutrients (N+P 2 O 5 +K 2 O) 1) 119 47 27 34 N P 2 O 5 K 2 O The demands of the major

Human urine has a potential to saving the natural resources. Nutrients in human urine 2) N:12 g/l P:1. g/l K:2. g/l 7.3 billions Urine excretion 1.

2 Introduction 2 N+P 2 O 5 +K 2 O [Mtons] Global consumption of nutrients (N+P 2 O 5 +K 2 O) 1) N P 2 O 5 K 2 O The demands of the major nutrients (N, P, K) for fertilizers are increasing. The nutrients are produced from mining minerals and fossil fuels which are limited resources. Human urine has a potential to saving the natural resources. Nutrients in human urine 2) N:12 g/l P:1. g/l K:2. g/l 7.3 billions Urine excretion 1. L/person/day Annual nutrients discharge N:32 Mtons (27%) P 2 O 5 :6.1 Mtons (13%) K 2 O:6.4 Mtons (19%) Human urine can contribute to the nutrient resources. 1) FAO, 215 2) Wilsenach et al., 27

3 Introduction 3 Urban area Urine collection system Peri-urban area Collection Transportation Farmlands Urine storage Collection and transportation cost of urine is huge owing to its volume. Urine volume reduction is important for reducing collection and transportation cost.

, 26) Reverse osmosis (RO) Forward osmosis (FO) Advantage Simple system for urine

4 Introduction 4 Concentration systems of urine Evaporative concentration (Masoom., 28) Electro dialysis (Pronk et al., 26) Reverse osmosis (RO) Forward osmosis (FO) Advantage Simple system for urine concentration A low energy consumption A low fouling tendency Applications in FO process 4) Seawater desalination Wastewater treatment Food processing 4) Cath et al., 26

5 Introduction 5 Osmotic pressure and concentration level 5) Fresh urine (ph ) Urea hydrolyzed urine (ph ) Concentration level Osmotic pressure (P Osm) [MPa] * Osmotic pressure of seawater is 2.5 [MPa]. The osmotic pressure of concentrated fresh urine has higher than that of seawater*. A draw solution requires high solute concentration for urine volume reduction. 5) Oishi., 213

6 Viscosity [mpa s] Introduction Draw solution Sucrose is a candidate for a draw It is easy to obtain solution. and a food additive Concentration [mol/l] Osmotic pressure [MPa] Sucrose solution has a very high viscosity at the high concentration. The high viscosity gives a thick boundary layer. Objectives To study Feasibility of urine concentration with sucrose draw solution in FO process Effect of concentration of sucrose on overall water permeability

7 Theory 7 Profile of concentration in membrane Water flux J w = P π = PRT a i,draw a i,feed i i Diffusion and convection as equation J w = D dc dx = k x dc dx x where J w is water flux [m/s], P is a water permeability coefficient [m/s/pa], π is a difference of osmotic pressure [Pa], R is the gas constant [J/K/mol], T is a temperature [K], a i is an activity of component i in the draw or feed solution [mol/m 3 ], C is a concentration in the draw or feed solution [mol/m 3 ], D is a diffusion coefficient [m 2 /s], k is an overall mass transfer coefficient [m/s], and x is a thickness of the membrane and the boundary layer.

is an overall mass transfer coefficient in boundary layer [m/s], L is a characteristic length [m], D is a diffusion coefficient [m 2 /s], Sc is the

8 Theory 8 Profile of concentration in membrane The Sherwood number Sh = kl D The equation for Sh calculation Sh =.664Sc 1/3 Re 1/2 The Schmidt number Sc = μ ρd x The Reynolds number Re = ρνl μ where C is a concentration in the draw or feed solution [mol/m 3 ], k is an overall mass transfer coefficient in boundary layer [m/s], L is a characteristic length [m], D is a diffusion coefficient [m 2 /s], Sc is the Schmidt number [-], Re is the Reynolds number [-], μ is a viscosity coefficient [Pa s], ρ is a density of solution [kg/m 3 ], and v is a flow velocity of solution at the membrane surface [m/s].

9 Material & methods: Run 1 9 Schematic diagram of FO test Flow direction Cross flow rate Membrane surface area Co-current 14 L/hr 98 cm 2 Run 1 Feed solution: Synthetic urine* (ph5.8) P Osm : 1.6 MPa, 5 ml Draw solution: Sucrose 2.5 mol/l (P Osm : 4.8 MPa), 2 ml Measurement FO test Ions by an ion chromatograph analyzer Urea by a LC/MS system Sucrose by a TOC analyzer *Composition of synthetic urine Salt Concentration [mol/l] MgCl 2 6H 2 O.32 NaCl.79 Na 2 SO 4.16 KCl.22 CaCl 2 H 2 O.44 KH 2 PO 4.31 NH 4 Cl.19 (NH 2 ) 2 CO (urea).42

10 Concentrations in feed [mol/l] Concentrations in draw [mol/l] Results & discussion: Run Concentrations of solutes in feed and draw solutions Urea Ions Sucrose Urea Ions Time [hr] Time [hr] Urea Sucrose Na + Cl - *K + NH 4 + +PO 4 3- Ca 2+ Mg 2 + SO 4 2- The concentrations of the ions in feed solution were increasing, while that of the sucrose in draw was diluted. The concentration of urea was slightly decreased in feed solution and increased in draw solution.

11 Results & discussion: Run 1 11 Urea [mol] NH 4 + [mol] Mass balances of urea and ammonium ion.25.2 Draw Feed Time [hr] Time [hr] Urea permeated from feed solution to draw solution. Ammonium ion did not pass through the membrane. Urea hydrolysis can contribute to concentration of nitrogen.

12 Water flux [1-6 m/s] Results & discussion: Run Effect of osmotic pressure difference on water flux y =.465 x R 2 =.965 Water flux J w = P π Water flux is proportional to the difference of osmotic pressure Δπ [MPa] The water flux was a linear correlation for the small osmotic pressure difference. But the water flux did not follow the liner linear correlation at the the large large osmotic pressure difference. A diffusion in a boundary layer should be considered for the water permeability.

Deionized water 5 ml FO test Draw solution: Sucrose.4,.5, 1., 2., and 2.6

13 Water flux [1-6 m/s] Material & methods: Run 2 13 Schematic diagram of FO test Cross flow rate Flow direction Membrane surface area 14 L/h Co-current 98 cm 2 Run 2 Feed solution: Deionized water 5 ml FO test Draw solution: Sucrose.4,.5, 1., 2., and 2.6 mol/l, 25 ml To calculate water permeability.2 J w = P π Calculation P = J w π Concentration [mol/l]

14 Results & discussion: Run 2 14 Water permeability [1-13 m/s/pa] Effect of sucrose concentration on water permeability Water permeability Concentration [mol/l] The high concentration of sucrose in draw solution gave a low water permeability.

15 Results & discussion: Run 2 15 Water permeability [1-13 m/s/pa] Overall mass transfer coefficient [1-5 m/s] Effect of sucrose concentration on water permeability and overall mass transfer coefficient Water permeability Mass transfer coefficient Concentration [mol/l] The overall mass transfer coefficient had a similar trend to the water permeability. The results suggested the relationship between the overall mass transfer coefficient and the water permeability.

16 Conclusions 16 Urine volume reduction was achieved by FO process. Ammonia did not pass through the membrane although urea permeated from feed to draw solution,. Urea hydrolysis can contribute to concentration of nitrogen. The overall mass transfer coefficient had a similar trend to the water permeability. This results suggested the relation between the overall mass transfer coefficient and the water permeability.

Forward Osmosis: Progress and Challenges

Forward Osmosis: Progress and Challenges Menachem Elimelech Department of Chemical and Environmental Engineering Yale University New Haven, Connecticut 2014 Clarke Prize Conference, November 7, 2014, Huntington