G. Zeeman

Publications (175)91.21 Total impact

• Article: Ammonium recovery and energy production from urine by a microbial fuel cell.

  P Kuntke, K M Smiech, H Bruning, G Zeeman, M Saakes, T H J A Sleutels, H V M Hamelers, C J N Buisman
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  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. · 4.86 Impact Factor
• Source

  Available from: John Parsons

  Article: Ecotoxicological assessment of grey water treatment systems with Daphnia magna and Chironomus riparius.

  L Hernández Leal, A M Soeter, S A E Kools, M H S Kraak, J R Parsons, H Temmink, G Zeeman, C J N Buisman
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  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. · 4.86 Impact Factor
• Article: Effects of ammonium concentration and charge exchange on ammonium recovery from high strength wastewater using a microbial fuel cell.

  P Kuntke, M Geleji, H Bruning, G Zeeman, H V M Hamelers, C J N Buisman
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  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.
  Bioresource technology 03/2011; 102(6):4376-82. · 4.25 Impact Factor
• Article: Removal of micropollutants from aerobically treated grey water via ozone and activated carbon.

  L Hernández-Leal, H Temmink, G Zeeman, C J N Buisman
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  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. · 4.86 Impact Factor
• Article: Energy and phosphorus recovery from black water.

  M S de Graaff, H Temmink, G Zeeman, C J N Buisman
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  ABSTRACT: Source-separated black water (BW) (toilet water) containing 38% of the organic material and 68% of the phosphorus in the total household waste (water) stream including kitchen waste, is a potential source for energy and phosphorus recovery. The energy recovered, in the form of electricity and heat, is more than sufficient for anaerobic treatment, nitrogen removal and phosphorus recovery. The phosphorus balance of an upflow anaerobic sludge blanket reactor treating concentrated BW showed a phosphorus conservation of 61% in the anaerobic effluent. Precipitation of phosphate as struvite from this stream resulted in a recovery of 0.22 kgP/p/y, representing 10% of the artificial phosphorus fertiliser production in the world. The remaining part of the phosphorus ended up in the anaerobic sludge, mainly due to precipitation (39%). Low dilution and a high pH favour the accumulation of phosphorus in the anaerobic sludge and this sludge could be used as a phosphorus-enriched organic fertiliser, provided that it is safe regarding heavy metals, pathogens and micro-pollutants.
  Water Science & Technology 01/2011; 63(11):2759-65. · 1.12 Impact Factor
• Article: Fate of hormones and pharmaceuticals during combined anaerobic treatment and nitrogen removal by partial nitritation-anammox in vacuum collected black water.

  M S de Graaff, N M Vieno, K Kujawa-Roeleveld, G Zeeman, H Temmink, C J N Buisman
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  ABSTRACT: Vacuum collected black (toilet) water contains hormones and pharmaceuticals in relatively high concentrations (μg/L to mg/L range) and separate specific treatment has the potential of minimizing their discharge to surface waters. In this study, the fate of estrogens (natural and synthetical hormones) and pharmaceuticals (paracetamol, metoprolol, propranolol, cetirizine, doxycycline, tetracycline, ciprofloxacin, trimethoprim, carbamazepine, ibuprofen and diclofenac) in the anaerobic treatment of vacuum collected black water followed by nitrogen removal by partial nitritation-anammox was investigated. A new analytical method was developed to detect the presence of several compounds in the complex matrix of concentrated black water. Detected concentrations in black water ranged from 1.1 μg/L for carbamazepine to >1000 μg/L for paracetamol. Anaerobic treatment was only suitable to remove the majority of paracetamol (>90%). Metoprolol was partly removed (67%) during aerobic treatment. Deconjugation could have affected the removal efficiency of ibuprofen as concentrations even increased during anaerobic treatment and only after the anammox treatment 77% of ibuprofen was removed. The presence of persistent micro-pollutants (diclofenac, carbamazepine and cetirizine), which are not susceptible for biodegradation, makes the application of advanced physical and chemical treatment unavoidable.
  Water Research 01/2011; 45(1):375-83. · 4.86 Impact Factor
• Article: Autotrophic nitrogen removal from black water: calcium addition as a requirement for settleability.

  M S de Graaff, H Temmink, G Zeeman, M C M van Loosdrecht, C J N Buisman
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  ABSTRACT: Black (toilet) water contains half of the organic load in the domestic wastewater, as well as the major fraction of the nutrients nitrogen and phosphorus. When collected with vacuum toilets, the black water is 25 times more concentrated than the total domestic wastewater stream, i.e. including grey water produced by laundry, showers etc. A two-stage nitritation-anammox process was successfully employed and removed 85%-89% of total nitrogen in anaerobically treated black water. The (free) calcium concentration in black water was too low (42 mg/L) to obtain sufficient granulation of anammox biomass. The granulation and retention of the biomass was improved considerably by the addition of 39 mg/L of extra calcium. This resulted in a volumetric nitrogen removal rate of 0.5 gN/L/d, irrespective of the two temperatures of 35 °C and 25 °C at which the anammox reactors were operated. Nitrous oxide, a very strong global warming gas, was produced in situations of an incomplete anammox conversion accompanied by elevated levels of nitrite.
  Water Research 01/2011; 45(1):63-74. · 4.86 Impact Factor
• Article: The effect of operational conditions on the hydrodynamic characteristics of the sludge bed in UASB reactors.

  R C Leitão, S T Santaellla, A C van Haandel, G Zeeman, G Lettinga
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  ABSTRACT: This work aims to evaluate the hydrodynamic properties of the sludge bed of Upflow Anaerobic Sludge Blanket (UASB) reactors based on its settleability and expansion characteristics. The methodologies used for the evaluation of the settleability of aerobic activated sludge, and for the expansibility of a sludge bed of Expanded Granular Sludge Bed reactors and Fluidised Bed Reactors were adapted and applied to the particular characteristics of the sludge of UASB reactors. An easy-to-build experimental set-up was developed to assess the parameters necessary for the equations of settleability and of expansibility. The results obtained from the sludges of seven differently operated reactors show that, for the treatment of low strength wastewater, settleability increased and expansibility decreased at decreased hydraulic retention time, from 6 to 1 h, and/or increased influent concentrations, from 136 to approximately 800 mg chemical oxygen demand/L. The results also show that it is useless to design an UASB reactor with a longer hydraulic retention time to cope with hydraulic shock loads, as a more expansible sludge will develop at such condition.
  Water Science & Technology 01/2011; 64(9):1935-41. · 1.12 Impact Factor
• Source

  Available from: Lucía Hernández Leal

  Article: Grey water treatment concept integrating water and carbon recovery and removal of micropollutants

  L Hernández-Leal, G Zeeman, H Temmink, C J N Buisman
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  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.
  Water Practice & Technology 01/2011; 2(6).
• Article: Bioflocculation of grey water for improved energy recovery within decentralized sanitation concepts.

  L Hernández Leal, H Temmink, G Zeeman, C J N Buisman
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  ABSTRACT: Bioflocculation of grey water was tested with a lab-scale membrane bioreactor in order to concentrate the COD. Three concentration factors were tested based on the ratio of sludge retention time (SRT) and hydraulic retention time (HRT): 3, 8 and 12. COD concentration factor was up to 7.1, achieving a final concentration of 7.2 g COD L(-1). Large fractions of suspended COD were recovered in the concentrate (57%, 81% and 82% at SRT/HRT ratios of 3, 8 and 12, respectively) indicating a strong bioflocculation of grey water. A maximum of 11% of COD mineralization of grey water was measured at the longest SRT tested (1 d). The integration of bioflocculation of grey water in decentralized sanitation concepts may increase the overall production of methane by 73%, based on the biogas produced by black water only. Therefore, bioflocculation is a promising grey water pre-treatment step for energy recovery within decentralized sanitation concepts.
  Bioresource technology 12/2010; 101(23):9065-70. · 4.25 Impact Factor
• Article: Long term partial nitritation of anaerobically treated black water and the emission of nitrous oxide.

  M S de Graaff, G Zeeman, H Temmink, M C M van Loosdrecht, C J N Buisman
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  ABSTRACT: Black water (toilet water) contains half the load of organic material and the major fraction of the nutrients nitrogen and phosphorus in a household and is 25 times more concentrated, when collected with a vacuum toilet, than the total wastewater stream from a Dutch household. This research focuses on the partial nitritation of anaerobically treated black water to produce an effluent suitable to feed to the anammox process. Successful partial nitritation was achieved at 34 degrees C and 25 degrees C and for a long period (almost 400 days in the second period at 25 degrees C) without strict process control a stable effluent at a ratio of 1.3 NO(2)-N/NH(4)-N was produced which is suitable to feed to the anammox process. Nitrite oxidizers were successfully outcompeted due to inhibition by free ammonia and nitrous acid and due to fluctuating conditions in SRT (1.0-17 days) and pH (from 6.3 to 7.7) in the reactor. Microbial analysis of the sludge confirmed the presence of mainly ammonium oxidizers. The emission of nitrous oxide (N(2)O) is of growing concern and it corresponded to 0.6-2.6% (average 1.9%) of the total nitrogen load.
  Water Research 04/2010; 44(7):2171-8. · 4.86 Impact Factor
• Article: The MobiSan approach: informal settlements of Cape Town, South Africa.

  A Naranjo, D Castellano, H Kraaijvanger, B Meulman, A Mels, G Zeeman
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  ABSTRACT: Pook se Bos informal settlement and the Cape Town Water & Sanitation Services Department are partnering on an urban sanitation project with a Dutch Consortium consisting of Lettinga Associates Foundation (LeAF), Landustrie Sneek and Vitens-Evides International. The aim of the project is to improve the basic sanitation services provided in informal settlements through the implementation of the MobiSan approach. The approach consists of a communal Urine-Diversion and Dehydration Toilet (UDDT) built in a former sea shipping container. The system is independent of water, electricity or sewerage connection and it is maintained by full-time community caretakers who also act as hygiene promoters. The project seeks to link sanitation services with hygiene promotion in informal settlements while enhancing user satisfaction and reducing costs in providing basic sanitation services. This paper describes the preliminary experiences and lessons learnt during the implementation and evaluation of the MobiSan prototype and discusses its potential for replication. The MobiSan has proved to be an appropriate option by means of dealing successfully with shallow groundwater table, land availability and high settlement densities. In addition it has been demonstrated to be cost-competitive in terms of operating cost compared to chemical toilets.
  Water Science & Technology 01/2010; 61(12):3078-90. · 1.12 Impact Factor
• Article: The effect of operational conditions on the sludge specific methanogenic activity and sludge biodegradability.

  R C Leitão, S T Santaellla, A C van Haandel, G Zeeman, G Lettinga
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  ABSTRACT: The effects of hydraulic retention time (HRT) and influent COD concentration (CODInf) on Specific Methanogenic Activity (SMA) and the biodegradability of an anaerobic sludge need to be elucidated because of the discordant results available in literature. This information is important for the operation of anaerobic reactors and design of the sludge post-treatment unit. For this study, sludge samples obtained from eight pilot-scale Upflow Anaerobic Sludge Blanket (UASB) reactors were tested. The reactors were fed with municipal wastewater and operated with different sets of HRT and influent concentrations until the steady state was established. The results show that at a lower HRT, sludge with relatively higher SMA develops. A slight trend of declining SMA at increasing CODInf was found for reactors operated at longer HRTs; however, further experiments are necessary for more definitive conclusions. The sludge from reactors operated at longer HRTs and with lower CODInf resulted in lower biodegradability. Results also showed that it is ineffective to design a UASB reactor with a longer HRT to cope with organic shock loads.
  Water Science & Technology 02/2009; 59(9):1847-53. · 1.12 Impact Factor
• Article: Effects of thermo-chemical pre-treatment on anaerobic biodegradability and hydrolysis of lignocellulosic biomass.

  T V Fernandes, G J Klaasse Bos, G Zeeman, J P M Sanders, J B van Lier
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  ABSTRACT: The effects of different thermo-chemical pre-treatment methods were determined on the biodegradability and hydrolysis rate of lignocellulosic biomass. Three plant species, hay, straw and bracken were thermo-chemically pre-treated with calcium hydroxide, ammonium carbonate and maleic acid. After pre-treatment, the plant material was anaerobically digested in batch bottles under mesophilic conditions for 40 days. From the pre-treatment and subsequent anaerobic digestion experiments, it was concluded that when the lignin content of the plant material is high, thermo-chemical pre-treatments have a positive effect on the biodegradability of the substrate. Calcium hydroxide pre-treatment improves the biodegradability of lignocellulosic biomass, especially for high lignin content substrates, like bracken. Maleic acid generates the highest percentage of dissolved COD during pre-treatment. Ammonium pre-treatment only showed a clear effect on biodegradability for straw.
  Bioresource technology 02/2009; 100(9):2575-9. · 4.25 Impact Factor
• Article: Implications of reactor type and conditions on first-order hydrolysis rate assessment of maize silage.

  C P Pabón Pereira, G Zeeman, J Zhao, B Ekmekci, J B van Lier
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  ABSTRACT: The biodegradability and first-order hydrolysis coefficient of maize silage have been assessed from batch experiments using different types of inoculum and substrate to inocula (S/I) ratios, and from CSTRs working at different hydraulic retention times (HRTs). In the batch experiments, the assessed maximum biodegradability of the maize silage was 68 (+/-2.7)% and 73(+/-2.9)% while the first order hydrolysis was 0.26 (+/-0.01) and 0.27(+/-0.02) d(-1), using granular and a mixture of granular and suspended inoculum, respectively. In the CSTR experiment biodegradability ranged from 41-65% depending on the HRT applied whereas the calculated first order hydrolysis coefficient was 0.32 d(-1). It is concluded that batch experiments can be used to assess first order hydrolysis constants and biodegradability provided that a well balanced inoculum is guaranteed. Further, it is shown that CSTR reactors digesting maize silage and operating at HRTs as low as 20 days can attain 88% of maximum biodegradability as long as pH fluctuations are minimized. 2 mmol NaHCO3 per gram maize silage was calculated to suffice for the purpose.
  Water Science & Technology 01/2009; 60(7):1829-36. · 1.12 Impact Factor
• Source

  Available from: ncsu.edu

  Article: Pretreatments to enhance the digestibility of lignocellulosic biomass.

  A T W M Hendriks, G Zeeman
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  ABSTRACT: Lignocellulosic biomass represents a rather unused source for biogas and ethanol production. Many factors, like lignin content, crystallinity of cellulose, and particle size, limit the digestibility of the hemicellulose and cellulose present in the lignocellulosic biomass. Pretreatments have as a goal to improve the digestibility of the lignocellulosic biomass. Each pretreatment has its own effect(s) on the cellulose, hemicellulose and lignin; the three main components of lignocellulosic biomass. This paper reviews the different effect(s) of several pretreatments on the three main parts of the lignocellulosic biomass to improve its digestibility. Steam pretreatment, lime pretreatment, liquid hot water pretreatments and ammonia based pretreatments are concluded to be pretreatments with high potentials. The main effects are dissolving hemicellulose and alteration of lignin structure, providing an improved accessibility of the cellulose for hydrolytic enzymes.
  Bioresource technology 08/2008; 100(1):10-8. · 4.25 Impact Factor
• Article: Anaerobic biodegradation of estrogens--hard to digest.

  T Z D de Mes, K Kujawa-Roeleveld, G Zeeman, G Lettinga
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  ABSTRACT: Although many publications are available on the fate of estrone (E1), 17beta-estradiol (E2) and 17alpha-ethynylestradiol (EE2) during aerobic wastewater treatment, little is published on their fate under strictly anaerobic conditions. Present research investigated the digestibility of E1 and EE2, using digested pig manure, granular UASB sludge, UASB-septic tank sludge and activated sludge as inocula. Besides, actual concentrations were measured in a UASB septic tank treating black water. Under anaerobic conditions E1 is reduced to E2 but the extent of this reduction depends on type of inoculum. No significant loss of the sum of E1 and E2 and of EE2 was observed. Adsorption was responsible for a 32-35% loss of E1 and E2 from the liquid phase in the UASB septic tank and the effluent still contained considerable concentrations of respectively 4.02 microg/l and 18.79 microg/l for E1 and E2 with a large fraction present in conjugated form. No EE2 was detected in the UASB effluent.
  Water Science & Technology 02/2008; 57(8):1177-82. · 1.12 Impact Factor
• Article: Characterisation and biological treatment of greywater.

  L Hernández Leal, G Zeeman, H Temmink, C Buisman
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  ABSTRACT: Characterisation of greywater was conducted in two different greywater streams in the Netherlands (Groningen and Sneek). The concentrations of macropollutants and nutrients measured were very different in both streams; in particular the COD was 425 mg/L in Groningen's water whereas in Sneek it was 1,583 mg/L. The aerobic treatment of greywater in a fed-batch reactor led to a 90% removal of COD at different organic loading rates. Anaerobically, the removal reached 40% COD removal on average, the possible reason being the high amount of surfactants present in the influent.
  Water Science & Technology 02/2007; 56(5):193-200. · 1.12 Impact Factor
• Article: Fate of oestrogens during anaerobic blackwater treatment with micro-aerobic post-treatment.

  T Z D de Mes, K Kujawa-Roeleveld, G Zeeman, G Lettinga
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  ABSTRACT: The fate of oestrone (E1), 17beta-oestradiol (E2) and 17alpha-ethynyloestradiol (EE2) was investigated in a concentrated blackwater treatment system consisting of an UASB septic tank, with micro-aerobic post-treatment. In UASB septic tank effluent a (natural) total concentration of 4.02 microg/L E1 and 18.69 microg/L E2, comprising the sum of conjugated (>70% for E1 and >80% for E2) and unconjugated forms, was measured. During post-treatment the unconjugated oestrogens were removed to below 1 microg/L. A percentage of 77% of the measured unconjugated E1 and 82% of E2 was associated with particles >1.2 microm in the final effluent implying high sorption affinity of both compounds. When spiking the UASB septic tank effluent with E1, E2, EE2 and the sulphate conjugate of E2, removal in the micro-aerobic post-treatment was >99% for both E2 and EE2 and 83% for E1. The lower removal value for E1 was a result of (slow) deconjugation during the treatment, and in the final effluent still 40% of E1 and 99% of E2 was present in conjugated form. The latter was the result of incomplete deconjugation of the spiked E2(3S) in the post-treatment system.
  Water Science & Technology 02/2007; 56(5):15-23. · 1.12 Impact Factor
• Article: Low-temperature post-treatment of anaerobically treated-sewage in anaerobic filter with cationic-polymer addition.

  T A Elmitwalli, R Raimundo, K Kujawa-Roelevel, G Zeeman
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  ABSTRACT: The post-treatment of domestic sewage pretreated in a 6 m3 UASB was investigated in two high-rate anaerobic filter (AF) reactors operated in parallel. The difference between the two AF reactors was only the addition of cationic polymer to the second reactor (AF + P). The reactors were operated at low temperatures, ranged between 13 and 20 degrees C. The media in each AF reactor consisted of vertical sheets of reticulated-polyurethane foam (RPF) with knobs. The results demonstrated that the AF + P reactor (HRT = 3 h) with cationic polymer addition (2 mg/L) was an efficient system for post-treatment. The removal efficiencies for total, suspended, colloidal and dissolved COD were, respectively, 41, 86 and 76 and 12% in the AF + P reactor and they were, respectively, 80, 97, 77 and 66% in the UASB + (AF + P) system. The removal of total, suspended and colloidal COD in the UASB + (AF + P) system were significantly higher than those achieved in the UASB + AF system. As hardly any nutrient was removed in the UASB + (AF + P) system, the effluent after pathogen removal is a valuable product for irrigation and fertilisation to close the water and nutrients cycle.
  Water Science & Technology 02/2006; 53(9):177-84. · 1.12 Impact Factor