Moving bed biofilm reactor to treat wastewater

This review carries out a comparative study of advanced technologies to design, upgrade and rehabilitate wastewater treatment plants. The study analyzed the relevant researches in the last years about the moving bed biofilm reactor process with only attached biomass and with hybrid biomass, which combined attached and suspended growth; both could be coupled with a secondary settling tank or microfiltration/ultrafiltration membrane as a separation system. The physical process of membrane separation improved the organic matter and NH₄ ⁺-N removal efficiencies compared with the settling tank. In particular, the pure moving bed biofilm reactor–membrane bioreactor showed average chemical oxygen demand, biochemical oxygen demand on the fifth day and total nitrogen removal efficiencies of 88.32, 90.84 and 60.17%, respectively, and the hybrid moving bed biofilm reactor–membrane bioreactor had mean chemical oxygen demand, biochemical oxygen demand on the fifth day and total nitrogen reduction percentages of 91.18, 97.34 and 68.71%, respectively. Moreover, the hybrid moving bed biofilm reactor–membrane bioreactor showed the best efficiency regarding organic matter removal for low hydraulic retention times, so this system would enable the rehabilitation of activated sludge plants and membrane bioreactors that did not comply with legislation regarding organic matter removal. As the pure moving bed biofilm reactor–membrane bioreactor performed better than the hybrid moving bed biofilm reactor–membrane bioreactor concerning the total nitrogen removal under low hydraulic retention times, this system could be used to adapt wastewater treatment plants whose effluent was flowed into sensitive zones where total nitrogen concentration was restricted. This technology has been reliably used to upgrade overloaded existing conventional activated sludge plants, to treat wastewater coming from textile, petrochemical, pharmaceutical, paper mill or hospital effluents, to treat wastewater containing recalcitrant compounds efficiently, and to treat wastewater with high salinity and/or low and high temperatures.     

Hydrogeology and sustainable future groundwater abstraction from the Agua Verde aquifer in the Atacama Desert,northern Chile

The hyper-arid conditions prevailing in Agua Verde aquifer in northern Chile make this system the most important water source for nearby towns and mining industries. Due to the growing demand for water in this region, recharge is investigated along with the impact of intense pumping activity in this aquifer. A conceptual model of the hydrogeological system is developed and implemented into a two-dimensional groundwater-flow numerical model. To assess the impact of climate change and groundwater extraction, several scenarios are simulated considering variations in both aquifer recharge and withdrawals. The estimated average groundwater lateral recharge from Precordillera (pre-mountain range) is about 4,482 m³/day. The scenarios that consider an increase of water withdrawal show a non-sustainable groundwater consumption leading to an over-exploitation of the resource, because the outflows surpasses inflows, causing storage depletion. The greater the depletion, the larger the impact of recharge reduction caused by the considered future climate change. This result indicates that the combined effects of such factors may have a severe impact on groundwater availability as found in other groundwater-dependent regions located in arid environments. Furthermore, the scenarios that consider a reduction of the extraction flow rate show that it may be possible to partially alleviate the damage already caused to the aquifer by the continuous extractions since 1974, and it can partially counteract climate change impacts on future groundwater availability caused by a decrease in precipitation (and so in recharge), if the desalination plant in Taltal increases its capacity.     

Seismically active fracture zones and distribution of thermal springs in Ecuador

Summary The analysis of the geometry of distribution of earthquake foci occurring in the continental South American plate above the subducted Nazca plate reveals that in the region of Ecuador these earthquakes accumulate in 8 well-separated fracture zones. These zones are interpreted as a system of deep seismically active fractures induced in the continental plate by the process of subduction. It is shown that the position of known thermal springs and of observed hydrothermal alterations in Ecuador correlates with the outcrops of the fracture zones.

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A simple theoretical interpretation of the cloud system in a dying cyclone from the aspect of the boucher-newcomb model

Резюме С помощью принятия простых кинематических предположений и на основании ω—уравнения выла определена конфигурация полос облаков в полностью окклюдированном циклоне без фронтов. Облачная система определяется полем скрытой теплоты, выделяемой в процессах конденсации. Полосы облаков теоретически представляют собой в основном листы синусоидальной спирали.

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Address: Boční II, Praha 4-Spořilov.     

Has climate change opened new opportunities for wheat cropping in Argentina?

As a result of climate change, and in particular rainfall changes, agricultural production is likely to change across the globe. Until now most research has focused on areas which will become unsustainable for agricultural production. However, there are also regions where climate change might actually improve conditions for growth. In the western Pampas region of Argentina, average annual rainfall has increased by 100–200 mm over the last 70 years, mainly during summer. Wheat is grown during winter, primarily on stored soil water and the main factor limiting plant production in this area is rainfall. Using the well tested simulation model APSIM-NWheat, we studied whether recent climate change has potentially opened new opportunities for wheat cropping in Argentina. Simulation results indicated that the additional rainfall in the Pampas of Argentina has increased the achievable yield (defined as the yield limited by solar radiation, temperature, water and nitrogen supply) of wheat in the currently cropped region, but less than expected based on the large amount of additional rainfall. The higher achievable yield from additional rainfall could potentially allow an expansion of profitable wheat cropping into currently non-cropped areas, where the achievable wheat yield increased in average from 1 t/ha to currently 2 t/ha. However, the poor water-holding capacity of the sandy soils which dominate the region outside the current cropping area limits the systems ability to use most of the increased summer rainfall. Nevertheless, the current higher achievable yield indicates a suitability of the region for cropping, which will slightly decline or remain unchanged depending on summer rainfall storage, with current and future climate change, including projected changes in rainfall, temperature and atmospheric CO₂ concentration. Factors other than just the achievable yield will eventually influence any future development of this region for cropping, including the high sensitivity of the sandy soils to erosion and nutrient leaching, current relatively high land prices, restrictions on clearing for cropping, the distance to the nearest port and current unsuitable cultivars withstanding the high frost risk.     

The ionosphere as an Alfven resonator in the Pc1 micropulsation range

Summary A local planar approximation of a stratified, inhomogeneous, anisotropic and dissipative ionosphere is presented as an Alfven quarter-wave plate resonator in the Pc1 micropulsation range. The frequency-amplitude structure of the resonance response of an isotropic Alfven wave on the Earth's surface and at a given altitude in the ionosphere is studied in comparison to standing waves in vacuum above an ideal conductor for a particular model of the ionosphere. An asymmetry in the response was found at both boundary of the resonator, at the Earth's surface and at the given altitude z₀. The results are related to the vertical changes of frequency dispersion in the dissipative medium of the ionosphere and to the vertical profile of the inhomogeneities of the resonator being considered.     

Time variation of earthquake activity in the Balkan region

Summary Three quantities M, E ^1/2 and E ^2/3 are used for studying the Balkan earthquake provinces. Most of them show a regular trend of activity, for some of them the observation period of 70 years is too short. Some graphs give evidence of the coincidence or migration of activity.     

Spatial distribution of crustaceans associated with shallow soft‐bottom habitats in a coral reef lagoon

The ecology and diversity of the shallow soft‐bottom areas adjacent to coral reefs are still poorly known. To date, the few studies conducted in these habitats dealing with macroinvertebrate fauna have focused on their abundance spatial patterns at high taxonomic levels. Thus, some aspects important to evaluate the importance and vulnerability of these habitats, such as species diversity or the degree of habitat specialization, have often been overlooked. In this study we compared the crustacean assemblages present in four different habitats at Magoodhoo Island coral reef lagoon (Maldives): coral rubble, sandy areas and two different seagrass species (Thalassia hemprichii and Cymodocea sp.). Forty‐two different crustacean species belonging to 30 families and four orders were found. ‘Site’ was a significant factor in all of the statistical analyses, indicating that tropical soft‐bottom habitats can be highly heterogeneous, even at a spatial scale between tens and hundreds of meters. Although traditionally it has been considered that seagrass beds host greater species diversity and abundance of organisms than adjacent unvegetated habitats, no differences in the univariate measures of fauna (abundance of organisms, number of species and Shannon diversity) were observed among habitats. However, sandy areas, coral rubble and seagrass beds exhibited different species composition of crustacean communities. The percentage of taxa considered as potential habitat specialists was 27% and the number of species exclusively occurring in one habitat was especially high in seagrass beds. Thus, degradation of this vegetated habitat would result in a great loss of biodiversity in tropical shallow soft‐bottom habitats.