Advanced phosphorus removal from membrane filtrates by adsorption on activated aluminium oxide and granulated ferric hydroxide.

The advanced phosphorus (P) removal by adsorption was studied for its suitability as a post-treatment step for membrane bioreactor (MBR) effluents low in P concentration and particle content. Two commercial adsorbents, granulated ferric hydroxide (GFH) and activated aluminium oxide (AA), were studied in batch tests and lab-scale filter tests for P adsorption in MBR filtrates. GFH showed a higher maximum capacity for phosphate and a higher affinity at low P concentrations compared to AA. Competition by inorganic ions was negligible for both adsorbents at the original pH (8.2). When equilibrium P concentrations exceeded 2 mg L(-1) in the spiked MBR filtrates, a precipitation of calcium phosphates occurred additionally to adsorption. During column studies the effluent criteria of 50 microgL(-1) P was reached after a throughput of 8000 bed volumes for GFH and 4000 for AA. Dissolved organic carbon appears to be the strongest competitor for adsorption sites. A partial regeneration and reloading of both adsorbents could be achieved by the use of sodium hydroxide.

Ozonation of polycyclic aromatic hydrocarbons in oil/water-emulsions: mass transfer and reaction kinetics.

The ozonation of highly condensed polycyclic aromatic hydrocarbons (PAH) was studied in oil/water-emulsions, which are comparable to poorly water-soluble PAH in industrial wastewaters and at contaminated sites. As there was a lack of knowledge about the ozonation in oil/water-emulsions, first the ozone mass transfer was studied and optimized from the gas to the water phase and from the water to the oil phase. The ratio of mass transfer and oxidation reaction was determined by the Hatta-number and revealed a slow, quasi homogeneous reaction of ozone with PAH inside the oil droplets. Because the ozone gas concentration had no influence under the optimized conditions, the selective PAH-ozonation could be described microkinetically by a direct ozone reaction of pseudo-first order regarding PAH-concentrations. The determined PAH mean reaction rate constants of 1.02 min(-1) in oil/water-emulsions are in the upper range as found for PAH dissolved in water. These results give a new insight into the ozonation in the three-phase systems and into the treatment of highly condensed, hardly biodegradable PAH.

Anion exchange resins for removal of reactive dyes from textile wastewaters.

Sorption onto an easily regenerable sorbent in fixed bed filters would be an interesting option for removal of reactive dyes from textile wastewaters. A previous screening with model solutions (Dyes Pigm 51 (2001) 111) had shown two anion exchangers (strong basic S6328a and weak basic MP62, both Bayer) to exhibit good sorption characteristics for reactive dyes. The aim of this study was to evaluate these materials more closely. Thus filter breakthrough, the behavior with original wastewater samples, and the effect of inorganic wastewater parameters as well as regeneration were studied. Breakthrough curves for both materials are relatively unfavorable with a flat gradient, but throughput until breakthrough (100-800 bed volumes) should be sufficient for technical use. With both resins dye uptake is influenced little by competition of inorganic anions (sulfate, carbonate, phosphate) and they perform well in original wastewaters. However, the weak basic type is only efficient up to pH 8. Alkaline regeneration works well for MP62, for S6328a acid regeneration works for most dyes.