Elmar Heinzle

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.

Present and potential applications of mass spectrometry for bioprocess research and control

For on-line monitoring of bioprocesses present applications are mainly restricted to gas analysis, but several techniques have been improved recently: membrane probes, the application of MS/MS techniques, methods of correlating available on-line data like gas reaction rates with bioprocess characteristics using stoichiometric models and other empirical correlations. New ionization and ion separation methods for biomolecules are developing dramatically. Most striking developments in this area are improved desorption techniques, electrospray, the renaissance of time-of-flight instruments and new challenges in ion trap techniques. Enormous progress is made in the analysis of peptides and other biopolymers. Combinations with new separation techniques like capillary electrophoresis and capillary HPLC show new horizons in biomolecule analysis.

Estimation of the time to maximum rate using dynamic DSC experiments

Abstract The probability of thermal risk may be described by the time to maximum rate under adiabatic conditions (TMR ad ). In this paper a screening method based on dynamic differential scanning calorimetry (DSC) measurements was studied in order to show that, when using the TMR ad criterion, no process would be assessed as safe when it could, in fact, be critical. The method of investigation was based on dynamic simulation. In this, the DSC measurement equipment and five different reaction types (simple nth order, consecutive, branched and autocatalytic reactions) were described in mathematical terms and simulated using MATLAB. The reliability of the estimation was checked by comparing the simulated TMR ad with the estimated TMR ad based on dynamic DSC measurements and isothermal assessment procedures. The TMR ad values calculated from simulation of dynamic DSC runs were always found to lie in the range of 10–70% of those obtained by dynamic simulation of the adiabatic case. Owing to some uncertainties with regard to autocatalytic reactions, a method was developed to identify them. The application of the total method to experimental measurements showed a good correspondence to the results obtained by simulation. The estimation method is therefore a good tool for preliminary screening and may be applied at the early stages in process design to save both time and money and without loss of safety.

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 .

Adaptive on-line optimal control of bioreactors: application to anaerobic degradation

Abstract The control of bioreactors is particularly important due to ever-changing reactor and feed conditions. In adaptive optimal control reactor, conditions are adjusted to obtain the best performance, as determined by a performance index (PI), which is often a function of more than one output variable. An empirical, linear input-output model is used whose parameters are updated at each sampling time using on-line measurements. In this example, for anaerobic wastewater treatment, two relations are used of the form, y 1 ( t ) = b 1 , 1 u ( t −1 - d 1 ) + c 1 ; y 2 ( t ) = b 2 , 1 u ( t − 1 − d 2 ) + c 2 . These are linear models relating feed flow rate, u, to methane production rate, y 1 , and organic acids concentration y 2 . The performance index (PI) was taken as a compromise between high methane rate and low organic acids as PI = methane production rate - Constant X (Total organic acids conc.). This was expressed in terms of the model parameters and maximized by the method of steepest ascent. In this way the feed rate could be continually adjusted for changing conditions, as caused by feed disturbances or biological adaptation. This dynamic optimization method has considerable advantage for slow systems, in that a steady state is not needed. One and two stage, anaerobic biofilm fluidized sandbed reactors were used to continuously degrade whey to biogas and residual organic acids. A PC computer was used to handle the on-line GC data and to serve as controller for the feed flow rate. Preliminary work involved testing conventional feedback control, for which pH setpoint control performed best. A complex simulation model based on mechanistic, dynamic mass balance-kinetic relations was established to describe the experimental response of the reactors. The simulation model was used to design the controller and to determine useful values for the control parameters; it proved extremely useful as it made lengthy experiments unnecessary. The PI function was shown by simulations to have a suitably sharp optimum. Automatic control experiments for one and two stage reactors were made in which responses were obtained for step changes in the performance index constant and for square wave increases in the feed concentration. The optimizer performed well, changing the feed rate to maintain the loading approximately constant with changed feed concentration. For a single stage system a new optimum was found after 5 h for a change in the PI constant and after 2 h for a step change in the feed concentration.

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.

Plant optimisation by retrofitting using a hierarchical method: Entrainer selection, recycling and heat integration†

Systematic procedures for reducing wastes in complex chemical plants are needed to allow efficient optimisation. A hierarchical procedure was applied to the optimisation of a real industrial plant to reduce wastes as well as energy and raw material consumption. In the case studied, the continuous production of methyl-butynol (MBI), acetylene reacts with acetone. The solvent ammonia and acetylene are recycled to the reactor. Unreacted substrates and by-products are separated from the product stream by distillation. Part of the unreacted acetone can be reused for other purposes after distillation. A substantial part of the unreacted substrates and by-products is delivered to a wastewater treatment plant. These waste streams constitute a substantial problem for the operation of this plant. First, waste streams were characterised and tracked back to their origin. Following the hierarchical design procedure, the overall input-output structure was fixed. The entrainer in the present process was critically examined and options were suggested. Then various recycle schemes were considered for later detailed study. The existing plant was simulated using ASPENPLUS. After adjusting the model to all important aspects of the real process scheme, excellent agreement between actual process performance data and simulation was obtained. The various process schemes were simulated and assessed for their economic and ecological performance. The objective functions used included utility, substrate and catalyst costs, as well as costs for wastewater treatment. Additionally, the environmental burden related to energy supply was accounted for by a carbon dioxide tax as suggested by the Nordic countries. The process changes included separation of unreacted acetone from the product stream and recycling to the reactor. By-products were converted back to substrates in an additional reactor separation system and recycled. In various simulated process configurations and operational schemes substantial economic and ecologic improvements were achieved. This study demonstrates the usefulness of hierarchical approaches combined with process simulation for plant optimisation.

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.