Harry Bruning

Ammonium recovery and energy production from urine by a microbial fuel cell

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.

Photocatalyzed oxidation of alcohols and organochlorides in the presence of native TiO2 and metallized TiO2 suspensions. Part(II): Photocatalytic mechanisms

A detailed description of various mechanisms for the photocatalytic oxidation of alcohols and organochlorides in an aerated or a deaerated system is given. This description includes mechanisms of surface reactions and radical reactions based on our experimental data presented. A surface mechanism of direct oxidation of substrates in photocatalyst surfaces is proposed as a favorable pathway for photocatalytic oxidations of methanol and ethanol, also a possible pathway for chloroform, trichloroethylene (TCE) and dichloropropionic acid (DCP) in M/TiO2 aqueous slurries.

Photocatalyzed oxidation of alcohols and organochlorides in the presence of native TiO2 and metallized TiO2 suspensions. Part (I): photocatalytic activity and pH influence

Photocatalytic oxidations of methanol, ethanol and chloroform, trichloroethylene (TCE), and dichloropropionic acid (DCP) in M/TiO2 aqueous slurries are studied. In the presence of oxygen, the intermediates of methanol oxidation, such as formaldehyde and formic acid, were not detected by GC in the slurries of TiO2, Pt/TiO2, or Pd/TiO2, and CO2 was the only product detected. The distribution of intermediates for ethanol photocatalytic oxidation varies with different catalysts: under the same reaction conditions, the ratio of acetaldehyde:acetic acid is 30:1 on TiO2, and 0.23:1 on Pt/TiO2, with the acetaldehyde concentration being 130 times higher on TiO2 than on Pt/TiO2. Thus, a further oxidation is achieved easily on the Pt/TiO2. The CO2 production depends on the initial reaction pH: Acidic pH produces CO2 immediately in alcohol oxidation, but alkaline pH retards the mineralization substantially. Little effect of Pd metallization on TiO2 was observed for photocatalytic oxidation of chloroform, TCE or DCP. Pt/TiO2 only enhances DCP dechlorination and has no effect on its decarboxylation.

Photochemical elimination of phenols and cod in industrial wastewaters

It is demonstrated that toxic pollutants such as phenols in industrial wastewaters can be eliminated efficiently by photochemical methods using a combination of UV and heterogeneous photocatalyst, and combinations of UV, H2O2, and ferric compounds. The combination of UV and photocatalyst even decreases the COD of some of the toxic industrial wastewater around 60–70% in 1–4 hour treatment time depending on the source of the wastewater. The different combinations of UV (200 W high pressure mercury lamp, wavelength 313 ≤ λ ≤ 456 nm), magnetite or aluminium oxide (as photocatalyst), H2O2 and iron compounds (FeCl3, Fe(NH3)2(SO4)2, as Fenton reagent) were used in lab scale experiments to examine the elimination at aerated conditions of pure phenol in solutions (initial concentration = 25 ppm) and of substituted phenols and COD in industrial wastewaters originally from phenolic resin manufacture, oil refinement, shale oil dry distillation, and naphthenic acid production. The results clearly show the separate and combined effect of UV, Ferric compounds and H2O2 on the elimination of phenols and COD.

Biodegradability and change of physical characteristics of particles during anaerobic digestion of domestic sewage.

At the high-rate anaerobic treatment of domestic sewage, both biological and physical processes play an important role. Therefore, the anaerobic biodegradability of raw, paper-filtered and membrane-filtered sewage and black water has been investigated in batch experiments. Additionally, the effect of anaerobic digestion on physical characteristics, like particle size, surface tension and zeta-potential, of the present particles is studied. The biodegradability of domestic sewage and black water at 30 degrees C is almost similar (71-74%). Moreover, a high methanogenesis of the colloidal fraction in domestic sewage (86 +/- 3%) is achieved, showing that the low removal of colloidal particles in continuous high-rate anaerobic reactors is due to low physical removal rather than biodegradability. The lowest biodegradability is demonstrated for the dissolved fraction (62%). The results show that after anaerobic digestion the average radius of particles with diameter < 4.4 and < 0.45 microns increased for domestic sewage, while it decreased for black water. Part of the surface-active components in domestic sewage is not biodegraded during anaerobic batch digestion, as indicated by the development of the surface tension. The negative zeta-potential of all particles hardly changes during digestion, showing that colloidal interactions were not affected by anaerobic digestion.

Low temperature treatment of domestic sewage in upflow anaerobic sludge blanket and anaerobic hybrid reactors

The treatment of sewage at a temperature of 13°C was investigated in three reactors (each 3.84 litre) a UASB and two anaerobic hybrid (AH) reactors with small sludge granules with an average diameter of 0.73 mm. The media used in the AH reactors were vertical polyurethane foam sheets. The reactors were operated at a HRT of 8 h. The use of small sludge granules and operating the reactors at low upflow velocity (1.8 m/d) improved suspended COD removal efficiencies for the UASB reactor. Moreover, the use of sheets in the AH reactors significantly increased suspended COD removal efficiencies as compared to the UASB and reached to 87% for pre-settled sewage treatment. The treatment of pre-settled sewage instead of raw sewage in AH reactors significantly increased colloidal and dissolved COD removal efficiencies with 13% and 12% respectively and colloidal COD removal efficiency for the UASB reactor with 13%. At ‘steady state’ for pre-settled sewage treatment, the AH reactors removed 64% of the total COD which is significantly higher by 4% than the UASB reactor. Therefore, the anaerobic treatment of domestic sewage at low temperature can be improved by treating pre-settled sewage in shallow AH reactors containing small sludge granules.

Effects of ammonium concentration and charge exchange on ammonium recovery from high strength wastewater using a microbial fuel cell

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.

Kinetic and mechanistic aspects of the oxidation of chlorophenols by ozone

In Advanced oxidation processes (AOPs) radicals are considered to play an important role. Organic contaminations can in AOPs generally be converted to carbon dioxide, water, etc. The most important limitation to the application of AOPs, however, is their high costs, especially when complete mineralisation of the pollutants is pursued. The costs can be reduced by using the oxidant more efficiently, which can be achieved by introducing selectivity. Kinetic and mechanistic data are the basic requirements for optimization of the process. In this work, the influence of several different parameters (temperature, pH, UV irradiation and carbonate concentration) on the kinetics of the degradation of ortho -chlorophenol and para -chlorophenol by ozone was investigated. The pH is the most important parameter. Strongly related to the pH is the degree of ionisation of the phenol, which might be of importance since the shift from a slow to a fast reaction occurs at a higher pH in the case of para -chlorophenol as compared to the case with the more acidic ortho -chlorophenol. A strong indication for a radical mechanism is found in the decrease of the reaction rate in the presence of carbonate, a well known radical scavenger. A further indication is seen in the first step of the reaction, which is dechlorination of the aromatic compound.

Photocatalyzed deposition and concentration of soluble uranium(VI) from TiO2 suspensions

Abstract A reversible, photocatalytic reductive deposition of uranium on TiO 2 or Pt/TiO 2 occurs in deaerated U(VI)/EDTA solutions, accompanied by CO 2 released from the oxidation of EDTA. A maximum of 50–60% uranium(VI) is deposited and an ultimate CO 2 release equivalent to a single decarboxylation of EDTA was reached under our experiment conditions no matter how long the illumination time. In aerated solutions, no uranium deposited, but a large CO 2 release still occurred, presumably from EDTA mineralization. Nearly 100% of the deposited, reduced products from uranium(VI) on TiO 2 . Pt/TiO 2 can be reoxidized and desorbed to regenerate dissolved uranium(VI) simply by solution exposure to air after illumination. The reductive deposition process can be repeated, indicating a potential cycle process. Modification of TiO 2 with platinum has only a slight influence on this reductive deposition of uranium on TiO 2 .

Anaerobic effluent disinfection using ozone: byproducts formation.

This research was aimed at studying oxidation processes, coliform inactivation effectiveness and disinfection byproducts (DBPs) associated with the disinfection of anaerobic sanitary wastewater effluent with ozone applied at doses of 5.0, 8.0 and 10.0mg O(3)L(-1) for contact times of 5, 10 and 15 min. The wastewater used in this research was generated by the wastewater treatment plant (WWTP), University of São Paulo - Brazil. The total coliform inactivation range was 2.00-4.06 log(10), and the inactivation range for Escherichia coli was 2.41-4.65 log(10). Mean chemical oxygen demand (COD) reductions were 37.6%, 48.8% and 42.4% for doses of 5.0, 8.0 and 10.0mg O(3)L(-1), respectively. Aldehyde formation varied with dosage only when the ozone dose was increased from 5.0 to 8.0mg O(3)L(-1) for acetaldehyde and from 5.0 to 8.0 and from 8.0 to 10.0mg O(3)L(-1) for glyoxal.