DENUTRITOR: REDUCTION OF BACTERIAL GROWTH AND
BIOFOULING IN WATER SYSTEMS
J. Gerritse*, B. van der Zaan, P. ter Huurne, G. Lengden, P. van Staveren,
S. Dilven, R. van der Arend, C. Beimfohr and W. van Tongeren
*Deltares, Princetonlaan 6, 3584 CB, Utrecht, The Netherlands,
Tel. +31630073547, Fax +31302564855
Topic 8: Water in the industry
Denutritor is a biofilter, which reduces the biofouling potential of water. In Denutritor microbial populations are grown in biofilms on porous filler material. The microorganisms in these biofilms degrade organic substrates, which are dissolved in the water. As a result, the source of microbial growth and biofouling is removed, and the potential for (re)use of the treated water is enhanced. In Aquafit4Use, laboratory and pilot scale Denutritor biofilters are tested for treatment of water from chemical and food industry, later followed by paper and textile industry.
Chemical Industry. Perstorp Specialty Chemicals aims to re-use effluent from their
wastewater treatment plant (WWTP) for cooling or other industrial processes. The reduction of biofouling potential was studied with laboratory Denutritor set-ups, fed with "synthetic" effluent from the wastewater treatment plant at Perstorp. Biofouling potential reduction was determined by measuring the difference between the amount of protein formed by microbial biofilms, growing on polyethylene (PE) tubes exposed to the influent or effluent water of Denutritor. Under stable operating conditions, a maximum reduction of biofouling potential of 86% was obtained.
Additionally, Deltares / TNO installed a Denutritor pilot on site at Perstorp (Figure 1). The pilot consists of three 13-litre columns placed in series, packed with different filler materials. For five months, the Denutritor operated on activated sludge effluent from Perstorp’s WWTP, with a flow rate of 0.3-0.5 m3/hr. Protein analyses of biofouling monitors show a 70% to 90% reduction of biofouling potential of the treated Perstorp WWTP water (Figure 2). No major difference was observed between the numbers of cultivable aerobic and coliform bacteria in Denutritor influent or effluent water. FISH analyses by Vermicon indicated that the bacteria in the effluent were in a starved physiological status, most likely because of depletion of growth substrates from the WWTP water. In samples from filler material of Denutritor it was observed that the bacterial biofilms were grazed by many protozoa and metazoa. A major fraction of the biofilms consisted of ammonia oxidising bacteria and nitrite oxidising bacteria, revealing an active nitrifying population (Figure 3). Pathogenic bacteria were not detected. WWTP water at Perstorp appeared to contain many particles and paper fibres. This caused problems with clogging of the fillers in the columns. After five months, the Denutritor pilot was switched to effluent of an MBR installation installed by Logisticon for treatment of Perstorp wastewater. With MBR effluent, clogging of Denutritor was much less a problem. The oxygen consumption of the pilot and protein formation on biofouling monitors indicated that MBR effluent had less biodegradable substrate and about five-fold lower biofouling potential than activated sludge effluent. Denutritor treatment reduced the biofouling potential of MBR effluent about 70%.
Food Industry. Unilever, Ben&Jerry’s
ice-cream factory in The Netherlands, is aiming to use collected rainwater for cleaning purposes. Therefore, we evaluated the use of Denutritor, in combination with UV disinfection, to reduce microbial growth and biofilm formation in rainwater. Laboratory experiments were done with rainwater, recirculated in a buffer tank via Denutritor. An identical system, but without Denutritor, was used as reference. The flow rate, hydraulic residence time, and dimension of the laboratory systems were adapted to the situation at the Ben&Jerry’s factory. The biofouling potential of rainwater appeared very low, and was further reduced (33%) by Denutritor. No major changes occurred in the concentrations of cultivable aerobic bacteria, but Denutritor appeared to reduce coliforms and E. coli in the rainwater. FISH analyses indicated that low concentrations of pathogens (Pseudomonas aeruginosa and Legionella) were present in the rainwater. UV disinfection effectively reduced the remaining bacterial contamination to acceptable levels for use of the rainwater. In summer 2010 Denutritor / UV pilot trials will be started at Unilever, Ben&Jerry’s factory to test the treatment of rainwater for cleaning purposes.
Figure 1. Picture of the Denutritor pilot
Figure 2. Reduction of biofouling potential of Perstorp WWTP water, measured on biofouling monitors
Figure 3. Fluorescent labelled ammonia oxidising bacteria from the filler of Denutritor
Biofouling potential (mg
protein/m2/day) Biofouling
potential reduction (%) Test run Influent Effluent Filter 1 Effluent Filter 2 Effluent Filter 3 1 (1 day) 45 19 12 9 80 2 (19 days) 5.0 2.4 2.4 0.4 92 3 (12 days) 5.3 3.0 3.3 1.5 71 4 (13 days) 5.8 4.4 3.3 0.7 88 5 (6 days) 8.4 2.9 1.4 1.1 87 Biofouling potential (mg
protein/m2/day) Biofouling
potential reduction (%) Test run Influent Effluent Filter 1 Effluent Filter 2 Effluent Filter 3 1 (1 day) 45 19 12 9 80 2 (19 days) 5.0 2.4 2.4 0.4 92 3 (12 days) 5.3 3.0 3.3 1.5 71 4 (13 days) 5.8 4.4 3.3 0.7 88 5 (6 days) 8.4 2.9 1.4 1.1 87
