Simultaneous treatment of hypersaline wastewaters and municipal wastewater in an osmotic membrane bioreactor ODEON project

Transcription

1 Simultaneous treatment of hypersaline wastewaters and municipal wastewater in an osmotic membrane bioreactor ODEON project Silvia Doñate Hernández Innovation Department Depuración de Aguas del Mediterráneo (DAM)

2 ODEON Membrane bioreactor process development for saline effluent management Project period July 2015 August Funding R&D State Programme for Societal Challenges RETOS (Spanish Ministry of Economy, Industry and Competitiveness -MINECO). Project partners ISIRYM (Research Institute for Industrial, Radiophysical and Environmental Safety) and IIAMA from Universitat Politècnica de València (UPV).

3 Introduction: forward osmosis Membrane processes driven by osmotic pressure difference between both membrane sides. ADVANTAGES: low operating cost, low membrane fouling DRAWBACKS: low permeate fluxes, cost of draw solution regeneration, reverse salt flux NEW MEMBRANES GOALS: HIGHER PERMEATE FLUX AND BETTER SELECTIVE PROPERTIES USE OF HYPERSALINE EFFLUENTS THAT CANNOT BE DIRECTLY TREATED OR MANAGED AS DRAW SOLUTIONS (CIRCULAR ECONOMY)

4 Introduction: osmotic membrane bioreactor (OMBR) Biomass is separated from treated wastewater by FO instead of UF/MF. Water dilutes the draw solution (i.e. Hypersaline wastewater) Advantages: Only water permeates trough the membrane High SRT enhances degradation of slow biodegradable organic compounds

5 Introduction: ODEON Objective Study the synergies between activated sludge processes and forward osmosis with high saline effluents at the biological process in an osmosis membrane bioreactor (OsMBR) Objectives: 1. Study of different industrial wastewaters as draw solutions in order to be used at the OsMBR fed with a mixture of urban wastewater with other waste flows from different industries. 2. Feasibility assessment of the forward osmosis (FO) combined to the activated sludge process in a OsMBR fed with urban wastewater mixed with high saline effluents. Operating conditions and membrane fouling.

6 Materials and methods Lab prototype: Plane membrane (CTA-NW from HTI, m2) Reactor volume: 1 l.

7 Materials and methods WWTP prototype: Start-up process with Porifera FO membrane of 1m2 (June 2018). Alzira WWTP. Flow: L/h Membrane flux: 5-10l/m2 h.

8 Materials and methods WASTEWATER TREATED AND DRAW SOLUTIONS. EXPERIMENT 1 WASTEWATER: tannery wastewater Parameter Value ph Conductivity (ms cm -1 ) COD (mg L -1 ) 1,497-3,468 DS: Absorption liquid effuent (ammonia absorption) Parameter Value ph 4* Conductivity (ms cm -1 ) 130 SO 4 (g L -1 ) 153 NH 4 -N (g L -1 ) 19 ph of ALE was around 1.2. NaOH was added to increase the ph for avoiding membrane damage.

9 Materials and methods WASTEWATER TREATED AND DRAW SOLUTIONS. EXPERIMENT 2 WATEWATER: Mixture of municipal wastewater and FTOP DRAW SOLUTION: FTOP FTOP: FERMENTATION BRINE FROM TABLE OLIVE PROCESSING (TYPICAL VALUES) ph 4 CONDUCTIVITY (ms/cm) 80 COD Cl 45000

10 Materials and methods Wastewater and Draw Solution Characterization (ph, conductivity, COD, NT, PT and Cl) MLSS, MLVSS to control organic load Soluble fraction of mixed liquor: COD,Conductivity, Soluble Microbial Products as proteins and carbohydrates. Membrane examination: before and after the experiment to check integrity. Hydrolysis Scanning emission microscope CELL SMP Diffusion

11 Results Membrane permeate flux comparison with Draw Solutions COD removal Flux and conductivity results SMP production: proteins and carbohydrates SEM analysis

12 Results Comparisons between Draw Solutions 10 9 ALE 8 FTOP 72 hours test feed: deionized water as FS. Jw (L m 2 h 1 ) Very similar osmotic pressure difference since permeate flux evolution with time was practically the same Time(hours)

13 Results COD removal COD removal efficiency (%) Time (d) COD in the DS (ALE and FTOP) was neligible. Membranes reject almost 100% of organic matter. Decrease of performance in reactor below 80% when: non-degradable organic matter and cellular debris accumulated high salinity in the mixed liquor Treatment by OMBR of industrial wastewaters with considerable non-biodegradable COD (tannery) may lead to operation problems : sludge withdrawals frequency Concerning to FTOP, phenols accumulation affected also the performance.

14 Results Experiment 1 Water flux Mixed liquor conductivity 4 40 Jw (LMH) 3,5 3 2,5 2 1,5 1 0, Time (d) Mixed liquor conductivity (ms cm) Flux and conductivity evolution versus time Decrease of the effective trans-membrane osmotic pressure due to salinity build-up in the bioreactor and the dilution of the DS. From the day 35-th of operation, less significant mixed liquor conductivity increase due to the concentration polarization phenomena

15 Results Experiment 2 Water flux Mixed liquor conductivity Jw (LMH) 4 3,5 3 2,5 2 1,5 1 0, Mixed liquor conductivity (ms/cm) Due to the operation strategy and low COD of the municipal wastewater (lower than 200 mg/l), the FTOP addition drived to a very fast salt increase in the reactor

16 Results SMP comparison SMP (mg L -1 ) test 1 test 2 Total experimental period PROTEINS: The faster increase of conductivity in the experiment 2 implied a higher SMP generation (especially proteins) SMP (mg L -1 ) test 1 test 2 Total experimental period CARBOHYDRATES: There were no significant differences in carbohydrate production

17 Results SEM analysis After osmotic driven backflush after the end of the experiments, membranes were examined. Salt precipitates (calcium sulfate in experiment 1) were observed. Membrane integrity was maintained.

18 Conclusions 1. The use of hypersaline wastewaters may have a great future in FO and in particular in OMBR. In this work, these effluents (FTOP and ALE) provided the driving force needed for the process. 2. The OMBR yielded a COD removal efficiency of practically 100% considering that no organic matter permeates through the membrane. 3. Salt accumulation may jeopardize the process. A fast increase of salt in the reactor enhanced the bacterial stress producing more SMPs (especially proteins). 4. Salt and non-degradable organic matter accumulation have to be reduced by frequent sludge withdrawals. The combination of OMBR and ultrafiltration (hybrid process) is of great interest to solve this problem. 5. Fouling was mainly reversible and membrane integrity was preserved during all the tests. 6. Other opportunities for FO: nutrient concentration and recovery, sludge drying, food processing, EC removal, etc.

19 Thanks for your attention!