POLYCERA: A NOVEL ULTRAFILTRATION MEMBRANE PROVIDING OPEX SAVINGS FOR RECLAIMED WASTEWATER APPLICATIONS. Introduction

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1 POLYCERA: A NOVEL ULTRAFILTRATION MEMBRANE PROVIDING OPEX SAVINGS FOR RECLAIMED WASTEWATER APPLICATIONS James A.Temple, Gil Hurwitz, Jinwen Wang, Anna Jawor, Subir Bhattacharjee, Eric Hoek Water Planet Inc, 8915 S. La Cienega Blvd, Unit C, Los Angeles, CA, james@waterplanet.com, Ph: Introduction Increasing fresh water demand in regions with highly stressed reservoirs continues to add unsustainable pressure on natural resources and negatively impact municipal and industrial operations. Recycling toxin-free reclaimed wastewater for water-intensive industrial processes or direct non-potable reuse not only provides a method to lower fresh water demand but also an economically competitive solution for end-users. Federal and state regulations for safe environmental discharge drive market demand for wastewater treatment technologies to produce a high-quality effluent. Membrane-based treatment solutions produce high fidelity filtrate quality well suited for reuse applications. However, dynamic feed qualities commonly found in these wastewaters can quickly foul conventional materials, requiring frequent chemical cleanings, curtailing membrane performance and shortening product lifetime. Most commercially available membranes are made of either ceramic or polymeric materials. Ceramic membranes are robust and hydrophilic; hence, fouling-tolerant, easy to clean and longlasting. Polymeric membranes are relatively affordable, but more fouling prone and less robust; hence, suffer from accelerated performance loss, frequent cleanings, and increased replacement rates. Water Planet, Inc has developed a high performance ultrafiltration (UF) membrane for secondary effluent wastewater polishing that combines the advantages of ceramic and polymeric membrane materials. Derived from novel nano-structured polymeric materials, PolyCera membranes provide ceramic-like thermal, mechanical and chemical robustness, while exploiting the high packing densities and favorable economics of polymeric form factors. PolyCera was tested to reclaim domestic wastewater for non-potable reuse at remote oil and gas production camps in South Texas. The membranes were implemented after aerobic biodegradation and clarification processes to provide final effluent for on-site industrial reuse (i.e., cement, drilling mud). Observed in field testing, PolyCera packaged in Water Planet s proprietary Spiral Monolith exhibits relatively higher sustainable fluxes and extended operating lifetime relative to conventional polyvinylidene difluoride (PVDF) membranes.

2 Materials and Methods Materials PolyCera Spiral Monolith modules were manufactured by Water Planet, Inc (BE-100-XB, Los Angeles, CA, USA). Spiral wound PVDF membranes were supplied by Synder Filtration (BN, Vacaville, CA, USA). Both PolyCera BE-100-XB and PVDF membranes had a nominal molecular weight cut-off of 100,000 Daltons. Process Centrally collected domestic wastewater from trailered camps on a remote oil and gas drilling pad was processed by two stages of aerobic media tanks. Effluent from the digestion tanks were discharged into a settling tank for clarification. Secondary effluent from the clarifier was directed into a 1µm pleated cartridge pre-filter (Flow-Max FMHC-170-1) and then into the ultrafiltration system. The installed ultrafiltration pilot system contained four 4 -diameter, 40 -length membranes with a total membrane area of 15.2m 2. Average system throughput was 2 gallons per minute (gpm) with a peak demand of 5 gpm. Typical feed water quality for this application is listed in Table 1. Over a six-week duration, approximately 210 hours of operating time was recorded. Table 1 Average UF system influent water quality Marker Average Value Unit Turbidity 78.6 ± 7 NTU E. coli 1 250,000 ± 0 CFU/100mL TSS 20.8 ± 8.1 mg/l Clean-in-Place (CIP) PolyCera CIP was performed using ambient temperature RO quality water (25 C) containing a solution of 1 wt% detergent (Alcojet, Alconox, Inc) at a ph of 11 in recirculation mode for 30 minutes. Cleaning of PVDF membranes was performed using the manufacturer-recommended protocol. Membrane Performance Optimum membrane permeability (liter/m2/hr/bar) was maintained using Water Planet s IntelliFlux control software. The system was equipped with an in-line turbidimeter which acquired real-time filtrate turbidity. Grab samples were analyzed for total suspended solids (TSS) and total E. coli testing, which were performed by Pollution Control Services (Universal City, TX) and San Antonio River Authority (San Antonio, TX) laboratories. 1. Maximum detection limit 2

3 Results and Discussion Marker Rejection Marker rejection was performed on the ultrafiltration system influent and membrane filtrate samples. Over the duration of the pilot, PolyCera membranes produced filtrate with an average turbidity of 0.01 NTU, never exceeding 0.5 NTU (Figure 1). PolyCera filtrate consistently rejected an average of over % (5-log removal) of E. coli, never exceeding 1 CFU/100mL (Figure 2). TSS was consistently rejected by the PolyCera membrane to the minimum detection limit of <1 mg/l (Figure 3). Figure 1 PolyCera filtrate turbidity acquired by in-line turbidimeter. Note: Values above 0.5 NTU at 90 hours were caused by air bubbles in the system during CIP. 3

4 Figure 2 E. coli analysis of UF system feed and PolyCera membrane filtrate grab samples. Figure 3 TSS analysis of UF system feed and PolyCera membrane filtrate grab samples. Comparative Study: Membrane Performance Average sustainable permeability of PolyCera BE-100-XB was 25 LMH/bar over 210 operating hours. PVDF membranes equilibrated at a sustainable permeability of 5 LMH/bar over 110 operating hours (Figure 4). 4

5 Figure 4 Permeabilities of PolyCera BE-100-XB (black) and PVDF (orange). Arrows depict when each CIP was executed. The higher sustainable permeability observed for PolyCera can be partly attributed to the efficacy of CIP as compared to PVDF. Although post-cip permeability of the PVDF membrane was recovered to approximately 60% of its original value, membrane fouling caused significant and immediate permeability loss. A sustainable permeability lower than 10 LMH/bar was reestablished within several hours after CIP. At 100 hours, filtrate flux was so low that it was not economical to operate the PVDF system any longer and it was subsequently shut down. However, the PolyCera membrane ran sustainably throughout the full 210-hour pilot. This was primarily due to the lower observed rate of membrane fouling compounded with the highly effective CIP. Full permeability recovery was observed after PolyCera cleaning, after which the membrane was conditioned to maintain a minimal rate of foulant deposition and permeability loss. Qualitatively, improved operating expenditures were observed with respect to the increased membrane lifetime (lower replacement cost) and reduced frequency of CIP (lower chemical and downtime costs). However, a longer-duration pilot needs to be performed to elucidate the exact impact on observed replacement and cleaning costs. 5

6 Conclusions PolyCera BE-100-XB provided high-quality effluent in a demanding industrial application suitable for high recovery water conservation and recycling. High rejection of bacteria, suspended solids, and turbidity were maintained over the full 200+ hour duration of the study. For comparison, a conventional PVDF membrane was also studied and found to equilibrate at a permeability 80% less than PolyCera. Membrane cleanings were much more effective for the PolyCera membranes as well, resulting in lower expected cleaning and replacement events. These observable benefits for the PolyCera membrane, such as increased membrane lifetime and improved efficacy/reduced frequency of CIP, will undoubtedly improve the overall operational costs of a PolyCera UF system as compared to one equipped with a conventional PVDF membrane. Future studies empirically measuring this behavior over extended operating scales (i.e., months) will provide operating expenditure savings versus commercial standards for specific industrial wastewater reuse applications. 6