Model experiments on improving nitrogen removal in laboratory scale subsurface constructed wetlands by enhancing the anaerobic ammonia oxidation.

Anaerobic ammonia oxidation (Anammox) has been identified as a new general process-strategy for nitrogen removal in wastewater treatment. In order to evaluate the role and effects of the Anammox process in wetlands, laboratory-scale model experiments were performed with planted fixed bed reactors. A reactor (planted with Juncus effusus) was fed with synthetic wastewater containing 150-200 mg L(-1) NH4+ and 75-480 mg L(-1) NO2(-). Under these operating conditions, the plants were affected by the high ammonia and nitrite concentrations and the nitrogen removal rate fell within the same range of 45-49 mg N d(-1) (equivalent to 0.64-0.70 g Nm(-2)d(-1)) as already reported by other authors. In order to stimulate the rate of nitrogen conversion, the planted reactor was inoculated with Anammox biomass. As a result, the rate of nitrogen removal was increased 4-5-fold and the toxic effects on the plants also disappeared. The results show that, in principle, subsurface flow wetlands can also function as an "Anammox bioreactor". However, the design of a complete process for the treatment of waters with a high ammonia load and, in particular, the realisation of simple technical solutions for partial nitrification have still to be developed.

Treatment of diglyme containing wastewater by advanced oxidation--process design and optimisation.

Diglyme (CAS No. 111-96-6), a biorefractive ether with teratogenic properties is of considerable importance as a solvent in the synthetic chemical industry. Results of lab-scale investigations into the optimal conditions for the oxidative mineralisation of 0.05 to 1 g/L of diglyme in synthetic process waters by hydrogen peroxide and ozone based advanced oxidation processes are presented. Fenton, photo-assisted Fenton and UV/H2O2 oxidation processes show acceptable TOC removals. At 50 degrees C the initial TOC removal rates varies between 0.07 and 6g TOC/L*h. The rates increase with the initial diglyme and hydrogen peroxide concentration as well as with the UV irradiation energy intensity. For example at a 1 g/l diglyme concentration a stoichiometric H2O2 addition resulted in TOC degradation of 60% to 70% after 30 minutes under the investigated conditions. Treatment with ozone/H2O2 at a pH of 8 and 25 degrees C required at least 100 minutes to achieve comparable mineralisation results. Biodegradability can be reached in far shorter times. Ozone on its own cannot be recommended for diglyme treatment. If complete mineralisation of diglyme is the objective, the UV/H2O2 oxidation process should be favoured. The ozone/H2O2 process might offer a viable alternative in cases where the oxidation step is followed by biological wastewater treatment, so that biodegradability is aimed at.