Advanced phosphorus removal via coagulation, flocculation and microsieve filtration in tertiary treatment.

The applicability of microsieve technology together with coagulation and flocculation for advanced phosphorus removal was investigated. A pilot unit including a microsieve with 10 µm mesh size was operated continuously with secondary effluent from Ruhleben wastewater treatment plant in Berlin. By applying a pretreatment of 0.07-0.09 mmol/L (as metal) coagulant and 1.5-2 mg/L cationic polymer, total phosphorus values below 80 µg/L were achieved. Coagulation with polyaluminum chloride (PACl) produced a better effluent quality compared to FeCl3, as less suspended solids and less residual coagulant were found in the microsieve effluent. In addition, the transmittance of UV radiation through the water was improved by using PACl. The produced amount of backwash water was always below 3% (on average 1.6%). Under optimized mixing conditions, polymer doses of 0.6 mg/L were possible without losses in water quality and filtration performance. Microsieving with chemical pretreatment is a viable option for high quality effluent polishing.

Comparing environmental impacts of tertiary wastewater treatment technologies for advanced phosphorus removal and disinfection with life cycle assessment.

Different technologies for tertiary wastewater treatment are compared in their environmental impacts with life cycle assessment (LCA). Targeting very low phosphorus concentration (50-120 µg/L) and seasonal disinfection of wastewater treatment plant (WWTP) secondary effluent, this LCA compares high-rate sedimentation, microsieve, dual media filtration (all with UV disinfection), and polymer ultrafiltration or ceramic microfiltration membranes for upgrading the large WWTP Berlin-Ruhleben. Results of the LCA show that mean effluent quality of membranes is highest, but at the cost of high electricity and chemical demand and associated emissions of greenhouse gases or other air pollutants. In contrast, gravity-driven treatment processes require less electricity and chemicals, but can reach significant removal of phosphorus. In fact, dual media filter or microsieve cause substantially lower specific CO2 emissions per kg P removed from the secondary effluent (180 kg CO2-eq/kg P, including UV) than the membrane schemes (275 kg CO2-eq/kg P).

Optimized removal of dissolved organic carbon and trace organic contaminants during combined ozonation and artificial groundwater recharge.

Pilot scale experiments using an 8 g/h ozonation unit and a 1.4 m(2) slow sand filter have demonstrated that the combination of ozonation and artificial groundwater recharge is suitable for efficient reduction of bulk and trace organics. The biodegradation of dissolved organic carbon (DOC) in the slow sand filter was enhanced from 22% without pre-treatment to 34% by pre-ozonation. In addition, realistic surface water concentrations of most investigated trace organic compounds (TrOCs) including carbamazepine, sulfamethoxazole, phenazone and metoprolol were reduced below the limits of quantification. Only a few TrOCs, e.g. primidone and benzotriazole, were not efficiently removed in both treatment steps and could be detected regularly in the filter effluent. For these compounds, enhanced treatment, such as advanced oxidation processes, needs to be considered. Testing for genotoxicity and cytotoxicity did not reveal any systematic adverse effects for human health. The formation of the by-product bromate from bromide was below the limit of the German drinking water directive of 10 µg/L. No removal of bromate was observed in the aerobic slow sand filter. Additional experiments with sand columns showed that operating a preceding bank filtration step to reduce DOC can reduce oxidant demand by approximately 20%.

Ozonation and reductive deiodination of iopromide to reduce the environmental burden of iodinated X-ray contrast media.

The potential of ozonation for the removal of iodinated X-ray contrast media (ICM) with focus on the oxidation products was examined. Iopromide used as model compound was dissolved in tap water, respectively in the effluent of a membrane bioreactor and was ozonated. Ozone (10 mg/L) was continuously introduced into a semi-batch reactor (35 L/h). After 30 minutes the ozone concentration was increased to 30 mg/L. In all experiments the iopromide concentration decreased very fast, whereas the decrease of the amount of organic bound iodine (AOI) was much lower. The concentration of iodate, the inorganic oxidation product increases with time, depending on the AOI decrease. The data clearly show that the ozonation of iopromide using a common applied ozone dosage leads to the formation of numerous iodinated transformation products, which are detectable by LC-ESI-MS. As an alternative treatment, especially for the treatment of urine or hospital waste water, the source for the contamination, it was tested if iopromide can be deiodinated by zero-valent iron. First experiments done in stirred batch reactors using iopromide dissolved in ultra pure water and urine with an initial pH of 2 showed that iopromide can be deiodinated completely by zero-valent iron. Even in contaminated urine collected in a hospital a deiodination of ICM was possible. Kinetic studies at constant pH showed that the deiodination can be described by pseudo-first order for equal iopromide and iron concentrations. The observed rate constant kobs increased with decreasing pH with a maximum at pH 3 with 4.76x10(-4) s(-1). The concentration of iopromide can be decreased by ozonation and by the reductive dehalogenation. In case of ozonation iodinated organic compounds are the main reaction products, whereas the reductive dehalogenation leads to transformation products which are not iodinated and are thus most probable biodegradable.

Long-lasting transneuronal dendritic changes of GABAergic neurons in the monkey dentate gyrus following entorhinal cortex lesion.

This study analyses dendritic changes of GABAergic neurons in the dentate gyrus of the African green monkey Cercopithecus aethiops upon lesioning of their main afferents, i.e., fibers originating form the entorhinal cortex (EC). Monkeys received a unilateral EC lesion (ECL) under visual control. Four, 10 and 365 days after surgery, GABAergic dentate neurons were immunostained for parvalbumin (PV). In comparison to the contralateral side, immunolabeled dendrites ipsilateral to the lesion appeared to be retracted from the outer portions of the molecular layer at all survival times. Dendritic changes were further analysed using an interactive neuron-tracing system. Whereas immunoreactive cell bodies were not reduced in number, the relative extension of dendrites throughout the dentate molecular layer was reduced by 40% 10 days postlesion (dpl) and recovered only up to 80% 365 dpl when compared with the control side. This was reflected by a decrease of the mean segment length, which included proximal dendrites and was apparent even after 365 dpl. The spread of the dendritic field was initially diminished by 50% and seemed to exhibit a long-lasting reduction. The findings are in line with previous results obtained in the rat, thus, indicating that similar transneuronal changes after ECL occur in the primate dentate gyrus. This may be of importance, since the EC appears to be a very early target area of affection in human neurodegenerative disorders, such as Alzheimer's disease.