Carbon,nitrogen and phosphorus recovery from liquid swine wastes: a review

Due to the pollution characteristics of the wastewater generated in piggeries, these waste streams have to be treated before discharging into the environment. These wastes have a high content of organic matter, nitrogen and phosphorus that can be converted or recovered into valuable products. The valuation of swine waste by anaerobic digestion has already been assessed, but no systematic review on the technologies used for recovering nutrients from this waste has been reported to date. Therefore, the present work has the goal of presenting the most studied technologies to different scales of recovery of carbon (i.e. organic matter), nitrogen and phosphorus from swine waste. The main characteristics and parameters of the processes involved in these technologies (mainly air stripping, membrane, enhance biological phosphorus removal and struvite formation) are also highlighted, pointing out its advantages and disadvantages and posing some final feasibility considerations on the subject addressed. Experiments reported in the literature proved that technologies used for nutrient recovery from swine waste are mostly applied to the effluents previously treated by anaerobic digestion as a primary treatment, and greater effort is required for the future implementation of these technologies in large scale. © 2020 Society of Chemical Industry     

Determining the domestic specific loads of two wastewater plants of the Paris conurbation (France) with contrasted treatments: a step for exploring the effects of the application of the European Directive

The effluents of wastewater treatment plants (WTTP) discharged into the rivers considerably affect the biogeochemical functioning of the system. In this paper, we characterize both raw and treated domestic wastewater from two WTTPs of Parisian agglomeration using different process treatments (Achères WWTP with a secondary treatment and Colombes WWTP with a tertiary one). In addition to the classical variables, we analyse the input of bacteria, both the heterotrophs and the nitrifyers. Tertiary treatment leads to significantly decrease ammonium-specific load (< 2 g KjN inhab equ.(-1) instead of 9 g KjN inhab equ.(-1) for secondary treatment) and notably reduces the one of organic matter (approximately 2.5 g biological oxygen demand (BOD) inhab equ.(-1) instead of approximately 7.5 g BOD inhab equ.(-1) for secondary treatment); it is therefore promising to improve oxygen status of both the Seine river and its estuary. In terms of total bacterial biomass abatement (the heterotrophs mostly), bioreactors (at Colombes WWTP) eliminate 12% more bacterial biomass than the activated sludge treatment (at Achères WWTP). Regarding the nitrifying bacteria, a tertiary treatment in bioreactors eliminates reverse similar 90% of both nitrifying bacteria and nitrogen pollution of wastewater. Bacterial populations are characterized by large size bacteria (> 1 microm) with a higher growth rate, that represent in the treatment plant effluents 70% of the biomass. These large size bacteria have therefore a strong impact in the organic matter degradation and oxygen consumption. Relationships between classical physical-chemical variables routinely analysed in WWTPs laboratory and bacterial biomass (heterotrophic and nitrifying) are established, in order to quantify the ecological role of the allochthonous bacteria brought into the river system. In addition, domestic specific loads are calculated for both raw and treated effluents of the two types of WWTPs. As the application of the European Water Directive requires to upgrade the wastewater treatment at Achères WWTP as soon as 2007 for 90% nitrification and 30% denitrification and in 2015 for further denitrification (up to 70%), the results of this study can be taken as point-source constraints into the modelling approach already developed for the Seine basin, and chosen to test the implementation of the Water Frame Directive.     

A long-term view of nutrient transfers through the Seine river continuum

A model (the Riverstrahler model) is used to describe nutrient transfer and transformation at the scale of the whole drainage network of the Seine based on information concerning the basic mechanisms governing N, P and Si inputs to the drainage network and in-stream transformation and retention. It was used to calculate the budget of these nutrients through the whole river continuum from land to sea. With the help of historical documents, the constraints used as forcing function in this model were reconstructed to express the changing conditions of land-use and urban population over the last five hundred years. The corresponding scenarios were run for different hydrological regimes including dry, mean and wet conditions. The results were validated on the long-term series of nutrient measurements spanning more than a century available at some stations on the Seine, upstream and downstream of the city of Paris. The model was also used to explore past and future trends in nutrient loading, retention and delivery to the coastal zone, in response to human management of the terrestrial watershed. Beside the initial pristine state, used as an idealized reference state (with N, P and Si delivered fluxes of about 45-110 kg N km(-2) yr(-1), 2-5 kg P km(-2) yr(-1), 510-1325 kg Si km(-2) yr(-1)), four periods were distinguished. The first one is that of the traditional cottage economy which prevailed, with quite a constant total population, until the end of the 18th century. N, P and Si fluxes were about 235-750 kg N km(-2) yr(-1), 15-60 kg P km(-2) yr(-1) and 425-1280 kg Si km(-2) yr(-1), depending on hydrological conditions. The second period, from the beginning of the 19th century to about the 1950's, corresponded to rapid increase in the total and urban population with a corresponding increase of point sources of N and P. From 1950 onwards, modern farming practices resulted in a dramatic increase in diffuse sources of nitrogen and to a lesser extent phosphorus: riverine N and P export reached 1320-2800 kg N km(-2) yr(-1), and 310-340 kg P km(-2) yr(-1): silica export remained fairly constant at around 410-1260 kg Si km(-2) yr(-1) depending on the hydrological conditions. In the 1990's, the fourth period is represented by a stabilized population and improved wastewater treatment, when the export of phosphorus is reduced to values as low as 40-60 kg P km(-2) yr(-1), but without as effective a reduction of nitrogen export. This represents an unprecedented situation for the marine coastal system, i.e. a shift from nitrogen to phosphorus limitation, as nitrogen is still delivered far in excess of the amount of silica available for diatom blooms.     

Querying dynamic communities in online social networks简

Online social networks （OSNs） offer people the opportunity to join communities where they share a common interest or objective. This kind of community is useful for studying the human behavior, diffusion of information, and dynamics of groups. As the members of a community are always changing, an efficient solution is needed to query information in real time. This paper introduces the Follow Model to present the basic relationship between users in OSNs, and combines it with the MapReduce solution to develop new algorithms with parallel paradigms for querying. Two models for reverse relation and high-order relation of the users were implemented in the Hadoop system. Based on 75 GB message data and 26 GB relation network data from Twitter, a case study was realized using two dynamic discussion communities：#musicmonday and #beatcancer. The querying performance demonstrates that the new solution with the implementation in Hadoop significantly improves the ability to find useful information from OSNs.     

Effects of the nature of the doping salt and of the thermal pre-treatment and sintering temperature on Spark Plasma Sintering of transparent alumina

A slurry of α-Al₂O₃ was doped with Mg, Zr and La nitrates or chlorides, in various amounts in the range 150-500 wt ppm and then freeze-dried to produce nanosized doped powder (∼150 nm). The powder was sintered by SPS to yield transparent polycrystalline alpha alumina. The influence of the nature of the doping element and the starting salt, the thermal treatment before sintering and the sintering temperature on the transparency of the ceramics were investigated. The transparency of the ceramics of nanosized Al₂O₃ was shown to depend mainly on the way the powder was prepared, the nature of the doping salt also had an effect. Finally, a high real inline transmittance, reaching 48.1% was achieved after optimization.     

Interfacial thermal resistance measurement between metallic wire and polymer in polymer matrix composites

The addition of thermally conductive particles is an effective way to increase thermal conductivity of polymers. For highly filled composites and therefore for a high effective thermal conductivity, the heat transfer at the matrix/particle interface becomes a key point to obtain further improvement. However the interfacial thermal resistance R_i between particles and matrix is difficult to measure because of the low sensitivity of temperature to R_i and because of the small size of the particles. A setup has been developed to measure R_i between nickel wires (fiber-like particles) of a few tens micrometer diameter and a polymer matrix. The temperature measurement of the heating wire associated with a thermal model allowed to estimate values of R_i between 0.3 × 10⁻⁵ and 1.6 × 10⁻⁵ m² K W⁻¹ and for various wire diameters and sample temperatures. Some R_i measurements have been validated using a thermo-elastic model.