Textile membranes systems as a simple approach to apply reclaimed water for safe reuse application, TU Berlin Centre for Water in Urban Areas
Objectives (i) decentralised and low cost ww treatment for safe reclamation in irrigation Sanitation (ii) increase availability of recycling water MDG 7
Conventional and MBR ww treatment Conventional WWTP screen sand grid settler biological reactor settler sandfiltration disinfection influent air effluent MBR WWTP screen sand grid influent biological reactor air effluent excess sludge excess sludge Modular and flexible Decentral plants Physical disinfection
Lp membranes in wastewater treatment: J s J w c 2 c 1 Concept of flux J w = k p k [ l / (m 2 h bar)]
Retention of Substances Nematodes water 0,0002 m. Influenza virus 0,1 m Haemoglobin 0,007 m Sodium-Ion 0,00037 m Pseudomonas Diminuta 0,28 m Giardia Lamblia and Cryptosporidium 3 à 6 m 0,0001 m Reverse osmosis 0,001 m 0,01 m 0,1 m Nanofiltration Ultrafiltration Microfiltration 1 m Streptococcus 1 m 10 m 100 m diameter of membrane pores
Immersed Membrane Modules (Hollow Fibre) Zenon Puron Mitsubishi Rayon
Immersed Membrane Modules (Plate & Frame)
Decentralised domestic MBR treatment Small scale plant BioMIR : for 4 to 8 persons 2 to 3 m³ reaktor volume 2.4 to 4.8 m² membrane area
Membrane materials Inorganic Ceramic (ZrO 2 ) Glass Metal Organic Celluloseacetate (CA) Polyamide (PA) Polyethersulfone (PES) Polyvinylidenfluorid (PVDF) Prices = 50 200 / m 2 oac CH 2 oac oh o O S O o Ac: OCOCH 3 n Polyethersulphone (PES) CH 2 CF 2 n Polyvinylidene fluoride (PVDF) CH 2 oac oac Cellulose Acetate (CA) o o oh o n
Characterization of clean ultrafiltration membranes Microdyn-Nadir UP 150 Microdyn-Nadir UV 200 MEMCOR AFM (5 x 5 µm) (clean(5)#4) (cleanalt(5)#2) (clean(5)#1) FE-SEM (50 000-fold) (50 000-fold) (50 000-fold) Type flat-sheet flat-sheet hollow-fiber Material hydrophilized PES PVDF PVDF MWCO nominal 150 kg/mol 200 kg/mol no data Pore size (FE-SEM) 25-35 nm 25-45 nm 20-40 nm Average roughness 3 1 nm 26 4 nm 46 8 nm Contact angle 50 65 65
Lp membranes flux vs. time Frequent backwash Flux 2 1 Irreversibles Fouling Reversibles Fouling t
MBR energy consumption Spec. energy demand [KWh/m 3 ] spezifischer Energiebedarf 1,6 kwh m³ 1,2 1 0,8 0,6 0,4 0,2 0 1,42 0,88 0,16 0,21 0,12 0,05 1,1 0,85 0,14 0,09 0,9 0,69 0,11 0,1 1100 2200 3300 m³/d Anlagendurchsatz Plant capacity [m 3 /d] 0,92 0,7 (Gildemeister, 2003) Membranstufe Membrane Rezirkulationspumpen Pumping Rührwerke Stirrer Feinblasige Aeration Belüfter Einlaufpumpwerk Inlet pumping Air-cycling stirring Economy of scale! < 0,8 kwh/m 3 Conventional treat. 0,21 kwh/m 3 (Wursthorn, 1998)
Standard MBR
Proposal of low budget TEX MBR Exchange of pumps by hydrostatic pressure Exchange of polymer membranes by textile materials
Avantages of textile membranes
Alternative membranes
Initial fluxes
Stationary fluxes
Critical flux phenomena (stainless steel, 10µm) Gradient of pressure [mbar/min] 39 19-1 critical flux at 12.6 LMH 0 10 20 30 40 Flux [L/m²h]
Sustainable flux for MBR systems
Development of an labscale Tex MBR system Three reactors: anerobic, anoxic, aerobic Total Reactorvolume = 1500 ml Flowrate = 150ml/h (HRT~ 15h) Membrane, textile, non-woven, 10µm, flux= 10 lmh Sediments
Labscale MBR system Non woven membrane
Labscale MBR Unit in operation Influent Effluent
Dissolved organic carbon INFLUENT EFFLUENT PARAMETER CONCENTRATION CONCENTRATION REMOVAL [%] (SD) MBR [mg/l] (SD) MBR [mg/l] (SD) CSB (n =24) 299 (± 121) 31.2 (± 8.3) 89 (± 6) DOC (n =34) 41.6 (± 20.8) 11.5 (± 1.7) 68 (± 10) 26
Nutrients: Nitrogen and Phosphorus N P stable and very good Nitrification Denitrification around 50% Due to difficulties with excess sludge phosphorus removal is only around 30% (incooperation) 27
Conclusions Textile membranes can be a substitute for organic polymer membranes in MBR treatment (by 100x cheaper) Non / woven textile membranes pore diameters > 1 µm. However the building up of a secondary membranes (EPS, biofouling) may allow good rejection rates for bacteria, protozoa and nematodes (lab scale MBR experiments) The membrane flux through these textiles should not exceed 10 LMH to avoid critical flux phenomena and sustainable operation. With low cost textiles and hydrostatic pressure operation (reduction of pumps, no backwash), Tex-MBR s can be a suitable decentralised wastewater treatment and reuse technique for irrigation Textile MBR might be further developed in a micro business approach