Issue 2

Denitrifying polyphosphate accumulating organisms (DNPAOs) are very promising for simultaneous nitrogen and phosphorus removal. While during denitrification, emission of a greenhouse gas, nitrous oxide (N₂O), may occur. In this study, DNPAOs were enriched in a lab-scale reactor, and N₂O emission was examined under different electron acceptor conditions. During the anoxic phase, with the uptake of phosphorus, denitrification of nitrate nitrogen (NO₃-N) was observed without the accumulation of nitrite nitrogen (NO₂-N). In general, a very low amount of N₂O was produced with nitrate as the electron acceptor, independent of the applied different nitrate concentrations. However, with nitrite as the electron acceptor, a much higher N₂O emission occurred. The N₂O emission factor to the denitrified NO₂-N was 6.2%, 5.3% and 4.9% at the initial NO₂-N concentration of 10, 20 and 40 mg l^-1, respectively. In addition, a much higher N₂O emission occurred with the co-existence of NO₃-N and NO₂-N. The initial organic carbon concentration had no significant effect on N₂O emission with NO₃-N as the electron acceptor. When stored organic carbon by DNPAOs was used as the electron donor, N₂O emission was mainly dependent on the electron acceptor. 

The photocatalytic activity of Mn doped TiO₂ for the ozonation of tetradifon pesticide in aqueous solution was studied. Various loadings of catalysts Mn/TiO₂ (1%, 2.5% and 5%) was prepared and characterized by standard analytical techniques. Photocatalyzed ozonation with 2.5% Mn/TiO₂ yielded 100% degradation and mineralization of tetradifon in 2.0 h under basic pH conditions. The extent of degradation of tetradifon pesticide and its mineralization were confirmed by GC-MS. For 10 mg/L of tetradifon, 0.1 g L⁻¹ of catalyst was found to be the optimum for effective mineralisation. The reused experiment confirmed that Mn/TiO₂ kept a good photocatalytic activity and stability, and it was a promising heterogeneous catalyst. The catalyst is fully recoverable and reusable multiple times with no loss of activity.

10 mg l^-1 and the permeate flux behavior during dead-end stirred-cell filtration system using six type of commercially available loose and tight NF membranes (NP010, NP030, NF90, NF270, CK3001 and DS-5DK). The rejection of CIPRO and permeate flux value were evaluated according to the effects of different parameters such as volume reduction factor (VRF), membrane type, transmembrane pressure (TMP) and pH. Contact angle and SEM measurements were also performed for the analysis of the pollution occurring in the pores and on the surfaces of the membranes. Filtration experiments for all membranes used indicated that the flux reached the steady state at VRF 3. CIPRO rejection was found to vary especially with both pH and membrane tightness. Despite the fact that, the loose NF membranes showed poor and variable CIPRO removal, the highest rejection was obtained with NF90 tight membrane at the original pH value (pH 5.65) and 10 bar of applied pressure. NF90 membrane achieved 98.3% TOC, 98.9% COD, 96.9% TDS and 95.7% E_c rejections at 24.39 L m^-2 h^-1 permeate flux at the predefined operating conditions. 

A dynamic mathematical model, based on the biochemical kinetic processes dominated in shallow free water systems was developed following the Activated Sludge Model (ASM) methodology. The model predicts plant mass and water uptake rate, BOD₅ and total nitrogen (TN) removal on a year round basis, given climatic data (temperature and rain variation). The model was developed based on the operation of two parallel pilot-plant basins, one with plants and one without. The dynamic model was used for the design of full scale constructed wetland facilities for given effluent quality requirements (average annual values of 25 mg l^-1 BOD₅ and 15 mg l^-1 TN). It is demonstrated that given inflow information, climatic data and effluent requirements, the required surface area to achieve adequate treatment while securing treated water effluent throughout the year can be determined. In addition, the required initial planting and the amount of plant mass that needs to be cropped on an annual basis is determined. It is also demonstrated that given a total wetland surface, the system performance is optimized if the wetland is divided into two sequential basins, the first with and the second without plants.