Comparison of biological and advanced treatment processes for ciprofloxacin removal in a raw hospital wastewater

Reuse of adsorption residuals for enhancing removal of ciprofloxacin from wastewater

Costs of water treatment can be reduced significantly if the spent adsorbents can be reused or regenerated. In this study, two residuals of iron adsorbed onto low-cost activated carbon (Fe-MCAC and Fe-MLAC) are reused as new adsorbents for the removal of ciprofloxacin (CIP) from pharmaceuticals wastewater. The residuals were characterized by SEM, XRD, FTIR, Raman spectra and N2-adsorption desorption. The adsorption mechanisms, performance, kinetics, isotherm, thermodynamic and reusability of residuals for CIP removal were evaluated. The isotherm data were well defined by the Freundlich model for both adsorbents (residuals). Moreover, the CIP adsorption follows the pseudo-second-order kinetic model. The maximum adsorption capacity of CIP on Fe-MCAC and Fe-MLAC was 476.19 and 416.67 mg/g, respectively. The maximum removal of CIP was obtained at pH 7 for both new adsorbents. The optimum contact time was found to be 30 and 60 min for Fe-MCAC and Fe-MLAC, respectively. The values of free energy change and enthalpy change for adsorption of CIP indicated the spontaneous, endothermic nature of the adsorption. In addition, the adsorption process was assisted by increasing randomness due to the value of entropy change. Therefore, the residuals of iron adsorption onto activated carbons could be reused as new low-cost adsorbents for antibiotics removal from wastewater.

Pyridine influence on a sequential anaerobic-anoxic-aerobic FMBR system for phenol, thiocyanate and ammonia removal

A synthetic wastewater containing various pyridine concentrations (25-250 mg/L) was treated in a sequential anaerobic(B1)-anoxic(B2)-aerobic(B3) fed batch moving bed reactor (FMBR) system. Pyridine was associated with phenol (1500 mg/L), SCN- (800 mg/L), chemical oxygen demand (COD) (5400-5430 mg/L) and NH4+-N (500 mg/L) at hydraulic retention time (HRT) of 6 (B1: 3 days; B2 and B3: 1.5 days each) days. In B1, pyridine removal was 10-12% from influent concentration of 25-100 mg/L and beyond that, it was zero. Removal of phenol (53-39%) and COD (33-22%) occurred in B1, but pyridine above 50 mg/L inhibited both. In B2, 68-90% of pyridine removal occurred along with phenol (>98%), COD (>67%), SCN- (>85%) removal and denitrification. In B2, with an increase in pyridine loading removal rate of phenol, COD and nitrate increased, whereas SCN- removal decreased beyond pyridine loading of 0.031g/L day. In B3, nitrification decreased with high generation of free ammonia. Pyridine degradation in B1, B2 and B3 follows the Stover-Kincannon model with a maximum substrate removal rate of 111.1, 333.3 and 23.81 g/L day, respectively. Thiocyanate removal in B2 and ammonia removal in B3 follows the Bhatia inhibition model with a maximum substrate removal rate of 0.641 and 0.528/day, respectively. The overall efficiency of the FMBR system remained unaffected up to 250 mg pyridine/L at 6 days HRT.

Reuse and recovery of raw hospital wastewater containing ofloxacin after photocatalytic treatment with nano graphene oxide magnetite

Inadequate treatment of hospital wastewater could result in considerable risks to public health due to its macro- and micropollutant content. In order to eliminate this problem, a new nanoparticle composite was produced under laboratory conditions and a photocatalytic degradation approach was used. Chemical oxygen demand (COD), biological oxygen demand (BOD₅), total suspended solids (TSS), total Kjeldahl nitrogen (TKN), total phosphorus (TP) (macro) and oflaxin (micro) pollutant removal were investigated with the nano graphene oxide magnetite (Nano-GO/M) particles by two different processes, namely adsorption and photodegradation. Low removal efficiencies (21-60%) were obtained in the adsorption process for the parameters given above, after 90 min contact time at a pH of 7.8 with 5 g/L Nano-GO/M composite. Using the photodegradation process, higher removal efficiencies were obtained with 2 g/L Nano-GO/M composite for COD (88%), TSS (82%), TKN (95%) and oflaxin (97%), at pH 7.8 after 60 min irradiation time at a UV power of 300 W. The synthesized nanoparticle was reused for two sequential treatments of pharmaceutical wastewater with no significant losses of removal efficiencies (for oflaxin 97%-90%). The quality of the treated hospital wastewater was first class according to the Turkish Water Pollution Control Regulations criteria. This water could also be used for irrigation purposes.