Oemer M. Kut

Removal of Chloro and Nitro Aromatic Wastewater Pollutants by Ozonation and Biotreatment

Synthetic wastewater containing a mixture of 10 different chloro and nitro aromatic pollutants was treated in batch ozonations and in a continuous combined ozonation-biodegradation system. The pH dependency of elimination of individual aromatics and of total organic carbon (TOC)was studied in batch ozonations. Experiments at pH 7 showed higher degradation and elimination rates than those at pH 2 and pH 12. A rapid increase of the dissolved ozone concentration after elimination of the aromatics was observed. This was very useful for on-line control of the combined process. Ozonation products were shown to be highly biodegradable through high oxygen uptake rates of biomass. Total mineralization of recalcitrant chloro and nitro aromatics was observed in the combined ozonation-biotreatment. Most significant improvement of ozone efficiency was obtained by controlling dissolved ozone concentration at optimal levels. A slight further enhancement was observed by recycling the liquid between the bioreactor and the ozone reactor.

Removal of substituted pyridines by combined ozonation/fluidized bed biofilm treatment

3-Methylpyridine (MP) and 5-ethyl-2-methylpyridine (EMP) were quantitatively removed in batch ozonation. Formate, acetate and oxalate where detected as ozonation products representing only about 10% of the total organic carbon after 90% removal of MP. Only 30% of the nitrogen was detected as nitrate. 5 moles of ozone were needed per mol of MP removed but at this time dissolved organic carbon (DOC) was only reduced by 10%. EMP was initially oxidised much faster but the reduction of DOC was only 5% when EMP was removed by 90%. Only 15% of the nitrogen was converted to nitrate. Small amounts of formate, acetate and oxalate were accumulated. 4 moles of ozone were required to remove one mole of EMP. In continuous combined experiments, wastewater was fed to a fluidised bed biofilm reactor with a mixed culture. The liquid was circulated through an ozonation bubble column. Ozone supply was controlled to keep the dissolved ozone concentration at a low level in the oxidation reactor. Complete mineralisation of MP and extensive mineralisation of EMP was observed during the whole experiment. During adaptation of biomass the ozone requirement decreased from 10 mol mol −1 of MP oxidised to 4 mol mol −1 .

Anaerobic-aerobic fluidized bed biotreatment of sulphite pulp bleaching effluents—II. Fate of individual chlorophenolic compounds

Abstract Four parallel biological fluidized bed reactor systems—one single aerobic, one single anaerobic and two combined anaerobic—aerobic reactors-were used to treat sulphite pulp chlorine bleaching wastewater. By total mass balances it was proven that the individual compounds followed were removed almost exclusively by biological degradation. The contribution of removal by adsorption on biomass was less than 1% for all the individual chlorophenolic compounds. In the three systems involving an aerobic step, 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol were usually quantitatively removed. This was observed up to loadings of 1 mmol 2,4,6-trichlorophenol per m 3 and day. At lower loading rates, trichloroguaiacols were also removed quantitatively. However, 4,5-dichloroguaiacol was only partly removed, whereas 3,5-dichlorosyringol was produced in the reactors from unidentified precursors. The anaerobic-aerobic recycle reactor did remove individual chlorinated phenolics at high loading rates better than the other reactor combinations. In the aerobic systems removal rates of organic chlorine and carbon correlated well with removal rates estimated from individual chlorophenols measurements, despite its low contribution to the total values (⪡1%).

Ozonation of wastewater containing N-methylmorpholine-N-oxide

Abstract Ozonation of synthetic wastewater containing N-methylmorpholine-N-oxide (NMMO) was investigated in batch experiments at different pH-values. Increasing pH caused higher initial elimination rates of NMMO as well as higher formation rates of nitrate. In mass transfer limited experiments, the shortest time needed for NMMO removal was observed at pH 7. This could be explained on the one hand through the importance of ·OH-radicals for the oxidation of NMMO and on the other hand through ozone decomposition reactions by ·OH-radicals at high pH-values. Dissolved ozone increased rapidly after elimination of NMMO at pH 7 and 8.5. High oxygen uptake rates of biomass with ozonation products showed the increase of the biodegradability compared to the initial synthetic wastewater. An improvement of ozone efficiency for elimination of NMMO and organic carbon can be expected in a process using a bioreactor in a recycle system.

Protection of biofilms against toxic shocks by the adsorption and desorption capacity of carriers in anaerobic fluidized bed reactors

The aim of this study was to select a support medium for an anaerobic biofilm fluidized bed reactor (AFBR) for waste water treatment. Six materials, shale, pumice, porous glass, quartz sand, activated carbon and anthracite were used as carriers for the biofilm. The reactors were operated in parallel for several months with vapour condensate from a sulfite cellulose process as feed. The criteria used for the evaluation were: a) Reproducibility of the reactor performance, b) performance of the different carriers under various loading rates, c) stability against toxic shock loadings using 2,4,6-trichlorophenol (TCP) as toxicant, d) recovery capacity after intoxication and starvation, e) adsorption/desorption behavior of the carriers.A comparison between four runs showed good reproducibility of the steady state removal rates. The performance of the reactors and the stability of the degradation rates were tested for a range of loading conditions. Unbuffered, buffered and pH controlled conditions were compared. The pumice carrier was best with respect to the degradation rate achieved per carrier mass. The response of the reactors to massive TCP step loadings was tested. Loadings less than 1.5 kg TCP/m3d resulted in initially normal gas production rates for all the systems, except the activated carbon, whose gas production was partially inhibited from the start. After increasing the load to 1.5 kg TCP/m3d the gas production rates of all the other reactors fell abruptly to zero. Restarting after 2 months, all reactors showed methanogenic activity without requiring new inoculum.Adsorption and desorption experiments with TCP showed that only the anthracite and activated carbon adsorbed appreciable amounts. The activated carbon had the greatest adsorption capacity but did not release the TCP by desorption, as did the anthracite.A bicomponent (pumice and anthracite) carrier mixture was compared in biological experiments with pumice and anthracite carrier alone, with and without TCP loading. The pumice and the carrier-mix performed equally well under non-toxic-loading conditions. With TCP toxic loading, the performance of the anthracite was superior. The anthracite carrier could be regenerated, owing mainly to its capacity for desorption.

Anaerobic-aerobic fluidized bed biotreatment of sulphite pulp bleaching effluents-I. Global parameters

Abstract Four parallel biological fluidized bed reactor systems-one single aerobic, one single anaerobic and two combined anaerobic-aerobic-have been used to treat sulphite chlorine pulp bleaching wastewater. It has been observed that the AOX removal was limited at 30%, independently of the wastewater dilution, mode of operation and retention time. Only small differences could be observed between the three systems involving an aerobic stage. The single aerobic reactor also gave rather competitive results with those having an additional anaerobic step, whereas the removal in the single anaerobic reactor was less than the three other systems. Only at high loading rates did the anaerobic-aerobic recycle reactor (AAR) perform better than the other systems. Constant NPOC/AOX ratio, before and after treatment, showed that the chlorinated material was degraded to the same extent as the non-chlorinated one. The removal by adsorption to biomass and biomass support material was less than 1 % for AOX.

Carrier Influence for the Treatment of Industrial Wastewaters in Anaerobic Biofilm Fluidized Bed Reactors

The continuous anaerobic degradation of vapour condensate from the cellulose process and brewery wastewater was investigated in parallel experiments using a variety of carriers in eleven single stage biofilm fluidized bed reactors. The carrier materials were shale, porous glass, quartz sand, activated carbon, pumice and anthracite. The reactors were operated for more than a year with vapour condensate from a sulphite cellulose process and mixed brewery wastewater as substrates. The performance and stability of the reactors with the respect to degradation rates were evaluated for a range of loading conditions. With the brewery waste, the highest degradation rates were obtained with the low-density and porous carriers, activated carbon and anthracite. Only the results with the brewery wastes are presented here.