Granular activated algae for wastewater treatment

The study used activated algae granules for low-strength wastewater treatment in sequential batch mode. Each treatment cycle was conducted within 24 h in a bioreactor exposed to 235 μmol/m²/s light intensity. Wastewater treatment was performed mostly in aerobic conditions, oxygen being provided by microalgae. High removal efficiency of chemical oxygen demand (COD) was achieved (86-98%) in the first hours of the reaction phase, during which the indicator's removal rate was 17.4 ± 3.9 mg O₂/g h; NH(4)(+) was removed during organic matter degradation processes with a rate of 1.8 ± 0.6 mg/g h. After almost complete COD removal, the (O⁺) remaining in the liquor was removed through nitrification processes promoted by the increase of the liquor's oxygen saturation (O₂%), the transformation rate of NH4(+) into NO(3)(-) increasing from 0.14 ± 0.05 to 1.5 ± 0.4 mg NH4(+)/g h, along with an O₂% increase. A wide removal efficiency was achieved in the case of PO(4)(3)(-) (11-85%), with the indicator's removal rate being 1.3 ± 0.7 mg/g h. In the provided optimum conditions, the occurrence of the denitrifying activity was also noticed. A large pH variation was registered (5-8.5) during treatment cycles. The granular activated algae system proved to be a promising alternative for wastewater treatment as it also sustains cost-efficient microalgae harvesting, with microalgae recovery efficiency ranging between 99.85 and 99.99% after granules settling with a velocity of 19 ± 3.6 m/h.

Dairy wastewater treatment using an activated sludge-microalgae system at different light intensities

A microalgae-bacteria system was used for dairy industry wastewater treatment in sequenced batch mode in a photobioreactor. The research investigated the influence of two light intensities: 360 and 820 μmol m(-2)s(-1) on treatment performances, microalgal cell recovery and dynamics of the protozoan community. Results showed that the light intensity of 360 μmol m(-2)s(-1) was found to be insufficient to support photosynthetic activity after the increase of bacterial biomass leading to the decrease of organic matter and ammonium removal efficiencies from 95 to 78% and 95 to 41%, respectively. Maximum microalgal cells recovery was about 63%. Continuous modification in the protozoan community was also noticed during this test. Increasing the light intensity to 820 μmol m(-2)s(-1) led to better microalgal cells recovery (up to 88%) and improved treatment performances. However, the decrease of protozoan richness to small flagellates and free-swimming ciliates was noticed. Moreover, the developed protozoan trophic network was found to be different from that identified in the conventional activated sludge system. The study emphasized that high increase of bacterial biomass promoted in nutrient- and organic matter-rich wastewater can strongly affect the treatment performances as a result of the shadow effect produced on the photoautotrophic microalgae aggregates.

Lessons learned from investigations on case study level for modelling of nutrient emissions in the Danube basin

In the framework of the project daNUbs (Nutrient Management in the Danube Basin and its Impact on the Black Sea) the MONERIS emission model is used for the basin wide calculation of nutrient (nitrogen and phosphorus) emissions in the Danube Basin. The MONERIS model was developed and successfully applied for German river catchments. Based on investigations in selected test regions (case studies) the daNUbs approach is to check the applicability of the MONERIS emission model for the specific conditions of the Danube Basin in more detail than is possible with a basin wide application. Six case studies with areas of 400-3,500 km2 and several subcatchments have been selected in order to represent different conditions along the Danube Basin. In this study region intensive data collection and enhanced monitoring has been performed in order to raise the database significantly above the generally available data. Water balance as well as nutrient balance calculations have been performed with the MONERIS model as well as with other approaches. Results are compared to each other and to data from monitoring. Results up till now showed the applicability and sensitivity of the MONERIS approach in different conditions of the Danube Basin (e.g. emissions via groundwater). They indicated that the nitrogen retention in the catchments is well described with the MONERIS model.

Considerations on the influence of extreme events on the phosphorus transport from river catchments to the sea

In this paper, results from rivers of different sizes in Romania, Hungary and Austria are presented. The paper shows the dynamics of extreme events and their contribution to the total P and suspended solids transported in these rivers. Special attention is paid to the influence of the size of the catchment and the event probability on the relative contribution of a single event to the total loads transported in the river. Further, the development of phosphorus loads along the Danube River at a flood event is shown. From the results it can be concluded that there is no immediate influence of high flow and flood events in upstream parts of the Basin on the transport of phosphorus from the catchment to the receiving Sea. Particle-bound phosphorus is mobilised from the catchment (through erosion) and the river bottom to a high extent at high flow events and transported at peak discharges to downstream, where retention by sedimentation of particles takes place. On the one hand this retention is a transport to flooded areas. In this case it can be considered as more or less long term retention. On the other hand sedimentation takes place in the riverbed, in case the tractive effort of the river is reduced. In this second case the P-pool in the sediments of the sedimentation area will be increased. If anaerobic conditions in the sediment appear, part of the phosphorus will be transformed to soluble ortho-phosphate and will continuously contribute to the phosphorus transport to the receiving sea. Part of the P-retained in the river sediment will be mobilised by resuspension at the next biggest high flow event. Altogether, these alternating processes of suspension, transport, export to flooded areas or sedimentation in the river bed with partly solution and partly resuspension at the next event decrease the share of the phosphorus transport during high flow events on the total loads transported in the more downstream parts of a catchments as compared to the more upstream parts. In the year of occurrence of an extreme flood event the P-transport of this year is dominated by the flood event. As an average over many years the contribution of high flow events to the total P-transport still may be between 7 and 20% in smaller catchments (around 1,000 km2). In a big catchment (e.g. river Danube) much smaller contributions of flood events on the total P-transport can be expected as an average over many years.

[Visual screening to discover ophthalmologic disorders in children]

PURPOSE

[corrected] To report the frequency of common childhood ocular disorders in a pediatric population. To address the issue of access to care for vision screening programs.

METHODS

Prospective vision screening for a period of 2 years (February 2001-February 2003) which enroll 254 children from 3 villages (Cepleniţa, Vlădeni, Aroneanu) sponsored by World Vision Romania. The study asses refractive errors, strabismus, amblyopia and other ocular abnormalities.

RESULTS

The mean age was 8.09 +/- 2.88 with the following distribution: preschool 19%, first grade 56%, second grade (over 10 years of age) 25%. Refractive errors requiring correction were observed frequently in this group of children (especially mild hyperopia, small myopia, astigmatic refractive errors). Strabismus was identified în 7.87% of cases and amblyopia în 11.42% (1/3 of cases mild and severe).

CONCLUSIONS

The frequency of common visual disorders in this population sample was larger than previously published studies. In poor economic subgroups the first ophthalmologic examination was performed after school age. Access to care is an integral part of any vision screening program. We are trying to highlight the importance of effective follow-up programs for all children especially those with limited resources for health care.