[show abstract][hide abstract] ABSTRACT: An innovative pilot-scale phototrophic biofilm reactor was evaluated over a 5-month period to determine its capacity to remove nitrogen and phosphorus from Dutch municipal wastewater effluents. The areal biomass production rate ranged between 2.7 and 4.5 g dry weight/m(2)/day. The areal nitrogen and phosphorus removal rates averaged 0.13 g N/m(2)/day and 0.023 g P/m(2)/day, which are low compared to removal rates achieved in laboratory biofilm reactors. Nutrient removal increased during the day, decreased with decreasing light intensity and no removal occurred during the night. Additional carbon dioxide supply was not requisite as the wastewater was comprised of enough inorganic carbon to sustain microalgal growth. The study was not conclusive for the limiting factor that caused the low nutrient removal rate, possibly the process was limited by light and temperature, in combination with pH increases above pH 9 during the daytime. This pilot-scale study demonstrated that the proposed phototrophic biofilm reactor is not a viable post-treatment of municipal wastewater effluents under Dutch climate conditions. However, the reactor performance may be improved when controlling the pH and the temperatures in the morning. With these adaptations, a phototrophic biofilm reactor could be feasible at lower latitudes with higher irradiance levels.
Applied biochemistry and biotechnology 10/2013; · 1.94 Impact Factor
[show abstract][hide abstract] ABSTRACT: This research demonstrated the selective production of n-butyrate from mixed culture by applying 2bar carbon dioxide into the headspace of batch fermenters or by increasing the initial substrate concentration. The effect of increasing initial substrate concentration was investigated at 8, 13.5 and 23gCOD/L with potato processing waste stream. Within 1week of incubation, n-butyrate fraction selectively increased up to 83% by applying 2bar hydrogen or 78% by applying carbon dioxide into the headspace whereas it was only 59% in the control reactor. Although the fraction of n-butyrate was elevated, the concentration remained lower than in the control. Both the highest concentration and fraction of n-butyrate were observed under the highest initial substrate concentration without headspace addition. The concentration was 10gCOD/L with 73% fraction. The operational conditions obtained from batch experiments for selective n-butyrate production were validated in a continuous process.
[show abstract][hide abstract] ABSTRACT: The objective of this investigation was to further increase the medium chain fatty acid (MCFA) production rate by reducing the hydraulic retention time (HRT) in an upflow anaerobic filter. The results showed that the volumetric MCFA production rate was increased to 57.4g MCFA l(-1)d(-1), more than 3 times higher than previous work. Despite the lower MCFA concentrations at 4h HRT, the MCFA selectivity remained above 80%. Extra carbon dioxide additions and higher yeast extract concentrations were required to increase the MCFA production rate. More research related to substrates and (micro)nutrients in mixed culture continuous reactors needs to be performed to reduce yeast extract use in chain elongation.
[show abstract][hide abstract] ABSTRACT: Heptanoate (or enanthate), a saturated mono-carboxylate with seven carbon atoms, is a commercially produced biochemical building block with versatile applications. Currently, heptanoate is mainly derived from the oxidation of heptaldehyde, which can be obtained after pyrolysis of castor oil. The objective of this investigation was to achieve efficient high rate heptanoate production using a mixed culture chain elongation process based on propionate and ethanol. An efficient high rate heptanoate production using chain elongation could offer an alternative for heptanoate production from castor oil. The investigation was performed in an upflow anaerobic filter with a hydraulic retention time of 17 h. A heptanoate production rate of 4.5 g l−1 d−1 was achieved with a heptanoate concentration of 3.2 g l−1. These results show sufficient potential to consider this approach as an alternative for heptanoate production from castor oil. Future research should make heptanoate production from propionate and ethanol more cost-effective.
[show abstract][hide abstract] ABSTRACT: Recently, interest has regained for medium chain fatty acids (MCFAs) as a low cost feedstock for bio-based chemical and fuel production processes. To become cost-effective, the volumetric MCFA production rate by chain elongation should increase to comparable rates of other fermentation processes. We investigate the MCFA production process at a hydraulic retention time of 17 h in an upflow anaerobic filter to improve the volumetric MCFA production rate. This approach resulted in a MCFA production with a volumetric production rate of 16.6 g l−1 d−1, which is more than seven times higher than the current production rate. Moreover the rate is now in the range of other fermentation processes like methane, butanol and ethanol production. Increasing the ethanol load lead to higher volumetric production rates and a high MCFA selectivity of 91%. During operation, methane percentages lower than 0.1% were detected in the headspace of reactor.
[show abstract][hide abstract] ABSTRACT: This study investigated the carboxylate spectrum from mixed culture fermentation of three organic waste streams after supplying 2 bar hydrogen and carbon dioxide or a mixture of these two gases to the headspace. Under any modified headspace, propionate production was ceased and butyrate, caproate and the total carboxylate concentrations were higher than in the reactors with N(2) headspace (control). Production of one major compound was achieved under hydrogen and carbon dioxide mixed headspace after 4 weeks of incubation. Both the highest acetate concentration (17.4 g COD/l) and the highest fraction (87%) were observed in reactors with mixed hydrogen and carbon dioxide headspace independent of the substrate used. In the control reactor, acetate made up maximum 67% of the total products. For other products, the highest concentration and fraction were seldom observed together. Selective butyrate production reaching a 75% fraction was found under the carbon dioxide headspace on the carbohydrate rich waste.
[show abstract][hide abstract] ABSTRACT: Nitrogen recovery through NH(3) stripping is energy intensive and requires large amounts of chemicals. Therefore, a microbial fuel cell was developed to simultaneously produce energy and recover ammonium. The applied microbial fuel cell used a gas diffusion cathode. The ammonium transport to the cathode occurred due to migration of ammonium and diffusion of ammonia. In the cathode chamber ionic ammonium was converted to volatile ammonia due to the high pH. Ammonia was recovered from the liquid-gas boundary via volatilization and subsequent absorption into an acid solution. An ammonium recovery rate of 3.29 g(N) d(-1) m(-2) (vs. membrane surface area) was achieved at a current density of 0.50 A m(-2) (vs. membrane surface area). The energy balance showed a surplus of energy 3.46 kJ g(N)(-1), which means more energy was produced than needed for the ammonium recovery. Hence, ammonium recovery and simultaneous energy production from urine was proven possible by this novel approach.
Water Research 02/2012; 46(8):2627-36. · 4.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: The objective of this research was to clarify the internal resistance of the PMFC. To characterize internal resistances of the PMFC current interrupt and polarization were used, and partial resistances were calculated. The internal resistance consisted mainly of anode resistance and membrane resistance which both decreased during current interrupt. The anode resistance was the result of mass transfer resistance in the electrochemically active biofilm. The membrane resistance was the result of accumulation of cations in the cathode. The polarization showed a distinct hysteresis which was explained by the increase of the internal resistance during polarization. The increase of this resistance makes it difficult to interpret the maximum power output of the PMFC.
[show abstract][hide abstract] ABSTRACT: Microalgae can be used for the treatment of municipal wastewater. The application of microalgal biofilms in wastewater treatment systems seems attractive, being able to remove nitrogen, phosphorus and COD from wastewater at a short hydraulic retention time. This study therefore investigates the area requirement, achieved effluent concentrations and biomass production of a hypothetical large-scale microalgal biofilm system treating municipal wastewater. Three scenarios were defined: using microalgal biofilms: (1) as a post-treatment; (2) as a second stage of wastewater treatment, after a first stage in which COD is removed by activated sludge; and (3) in a symbiotic microalgal/heterotrophic system. The analysis showed that in the Netherlands, the area requirements for these three scenarios range from 0.32 to 2.1 m2 per person equivalent. Moreover, it was found that it was not possible to simultaneously remove all nitrogen and phosphorus from the wastewater, because of the nitrogen:phosphorus ratio in the wastewater. Phosphorus was limiting in the post-treatment scenario, while nitrogen was limiting in the two other scenarios. Furthermore, a substantial amount of microalgal biomass was produced, ranging from 13 to 59 g per person equivalent per day. These findings show that microalgal biofilm systems hold large potential as seasonal wastewater treatment systems and that it is worthwhile to investigate these systems further
Water Research - WATER RES. 01/2012; 4(2):460-473.
[show abstract][hide abstract] ABSTRACT: In order to meet environmental quality criteria, grey water was treated in four different ways: 1) aerobic 2) anaerobic+aerobic 3) aerobic+activated carbon 4) aerobic+ozone. Since each treatment has its own specific advantages and disadvantages, the aim of this study was to compare the ecotoxicity of differently treated grey water using Chironomus riparius (96 h test) and Daphnia magna (48 h and 21d test) as test organisms. Grey water exhibited acute toxicity to both test organisms. The aerobic and combined anaerobic+aerobic treatment eliminated mortality in the acute tests, but growth of C. riparius was still affected by these two effluents. Post-treatment by ozone and activated carbon completely removed the acute toxicity from grey water. In the chronic toxicity test the combined anaerobic+aerobic treatment strongly affected D. magna population growth rate (47%), while the aerobic treatment had a small (9%) but significant effect. Hence, aerobic treatment is the best option for biological treatment of grey water, removing most of the toxic effects of grey water. If advanced treatment is required, the treatment with either ozone or GAC were shown to be very effective in complete removal of toxicity from grey water.
Water Research 12/2011; 46(4):1038-44. · 4.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: In a Plant-Microbial Fuel Cell anode-conditions must be created that are favorable for plant growth and electricity production. One of the major aspects in this is the composition of the plant-growth medium. Hoagland medium has been used until now, with added phosphate buffer to reduce potential losses over the membrane because of differences in pH between anode and cathode. We developed a new, improved plant-growth medium that improves current production, while the plant keeps growing. This medium is a nitrate-less, ammonium-rich medium that contains all macro- and micro-nutrients necessary for plant growth, with a balanced amount of bicarbonate buffer. Sulphate presence in the plant-growth medium helps to keep a low anode-potential. With the new plant-growth medium the maximum current production of the Plant-Microbial Fuel Cell increased from 186 mA/m(2) to 469 mA/m(2).
[show abstract][hide abstract] ABSTRACT: Microalgal biofilms have so far received little attention as post-treatment for municipal wastewater treatment plants, with the result that the removal capacity of microalgal biofilms in post-treatment systems is unknown. This study investigates the capacity of microalgal biofilms as a post-treatment step for the effluent of municipal wastewater treatment plants. Microalgal biofilms were grown in flow cells with different nutrient loads under continuous lighting of 230 μmol/m(2)/s (PAR photons, 400-700 nm). It was found that the maximum uptake capacity of the microalgal biofilm was reached at loading rates of 1.0 g/m(2)/day nitrogen and 0.13 g/m(2)/day phosphorus. These maximum uptake capacities were the highest loads at which the target effluent values of 2.2 mg/L nitrogen and 0.15 mg/L phosphorus were still achieved. Microalgal biomass analysis revealed an increasing nitrogen and phosphorus content with increasing loading rates until the maximum uptake capacities. The internal nitrogen to phosphorus ratio decreased from 23:1 to 11:1 when increasing the loading rate. This combination of findings demonstrates that microalgal biofilms can be used for removing both nitrogen and phosphorus from municipal wastewater effluent.
Water Research 09/2011; 45(18):5925-33. · 4.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: Ozonation and adsorption onto activated carbon were tested for the removal micropollutants of personal care products from aerobically treated grey water. MilliQ water spiked with micropollutants (100-1600 μgL(-1)) was ozonated at a dosing rate of 1.22. In 45 min, this effectively removed (>99%): Four parabens, bisphenol-A, hexylcinnamic aldehyde, 4-methylbenzylidene-camphor (4MBC), benzophenone-3 (BP3), triclosan, galaxolide and ethylhexyl methoxycinnamate. After 60 min, the removal efficiency of benzalkonium chloride was 98%, tonalide and nonylphenol 95%, octocrylene 92% and 2-phenyl-5-benzimidazolesulfonic acid (PBSA) 84%. Ozonation of aerobically treated grey water at an applied ozone dose of 15 mgL(-1), reduced the concentrations of octocrylene, nonylphenol, triclosan, galaxolide, tonalide and 4-methylbenzylidene-camphor to below limits of quantification, with removal efficiencies of at least 79%. Complete adsorption of all studied micropollutants onto powdered activated carbon (PAC) was observed in batch tests with milliQ water spiked with 100-1600 μgL(-1) at a PAC dose of 1.25 gL(-1) and a contact time of 5 min. Three granular activated carbon (GAC) column experiments were operated to treat aerobically treated grey water. The operation of a GAC column with aerobically treated grey water spiked with micropollutants in the range of 0.1-10 μgL(-1) at a flow of 0.5 bed volumes (BV)h(-1) showed micropollutant removal efficiencies higher than 72%. During the operation time of 1728 BV, no breakthrough of TOC or micropollutants was observed. Removal of micropollutants from aerobically treated grey water was tested in a GAC column at a flow of 2 BVh(-1). Bisphenol-A, triclosan, tonalide, BP3, galaxolide, nonylphenol and PBSA were effectively removed even after a stable TOC breakthrough of 65% had been reached. After spiking the aerobically treated effluent with micropollutants to concentrations of 10-100 μgL(-1), efficient removal to below limits of quantification continued for at least 1440 BV. Both ozonation and adsorption are suitable techniques for the removal of micropollutants from aerobically treated grey water.
Water Research 03/2011; 45(9):2887-96. · 4.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: Ammonium recovery using a two chamber microbial fuel cell (MFC) was investigated at high ammonium concentration. Increasing the ammonium concentration (from 0.07 to 4 g ammonium-nitrogen/L) by addition of ammonium chloride did not affect the performance of the MFC. The obtained current densities by DC-voltammetry were higher than 6A/m(2) for both operated MFCs. Also continuous operation at lower external resistance (250 Ω) showed an increased current density (0.9A/m(2)). Effective ammonium recovery can be achieved by migrational ion flux through the cation exchange membrane to the cathode chamber, driven by the electron production from degradation of organic substrate. The charge transport was proportional to the concentration of ions. Nonetheless, a concentration gradient will influence the charge transport. Furthermore, a charge exchange process can influence the charge transport and therefore the recovery of specific ions.
[show abstract][hide abstract] ABSTRACT: A total treatment concept was developed for grey water from 32 houses in Sneek, The Netherlands. A
thorough characterization of COD, nutrients, metals, micropollutants and anions was carried out. Four
biological treatment systems were tested: aerobic, anaerobic, combined anaerobic + aerobic and a
bioflocculation system. Micropollutants were measured in grey water and effluent from three biological
treatment systems. The best performing biological treatment system, the aerobic one showed the highest
COD and micropollutant removal at a low sludge yield. The bioflocculation system could concentrate 70% of the COD of grey water into a concentrated stream. Advanced treatment with ozone and activated carbon
showed to be effective to remove all micropollutants below limits of quantification. A total treatment system
is proposed based on the pre-treatment with a bio-flocculation system, aerobic post-treatment and ozonation as a disinfection and micropollutant removal step.