Phosphorus recovery from municipal and fertilizer wastewater: China's potential and perspective

Phosphorus (P) is a limited resource, which can neither be synthesized nor substituted in its essential functions as nutrient. Currently explored and economically feasible global reserves may be depleted within generations. China is the largest phosphate fertilizer producing and consuming country in the world. China''s municipal wastewater contains up to 293,163 Mg year of phosphorus, which equals approximately 5.5% of the chemical fertilizer phosphorus consumed in China. Phosphorus in wastewater can be seen not only as a source of pollution to be reduced, but also as a limited resource to be recovered. Based upon existing phosphorus-recovery technologies and the current wastewater infrastructure in China, three options for phosphorus recovery from sewage sludge, sludge ash and the fertilizer industry were analyzed according to the specific conditions in China.     

Challenges to measuring,monitoring, and addressing the cumulative impacts of artisanal and small-scale gold mining in Ecuador

Portovelo-Zaruma, Ecuador is an artisanal and small-scale gold mining (ASGM) region with approximately 6000 gold miners working with mercury and cyanide. Although artisanal gold mining (AGM) has taken place in Portovelo-Zaruma for centuries, highly mechanized small-scale gold mining (SGM) processing plants capable of increased throughput began being built in the 1990s. While there are benefits associated with ASGM, there are also negative impacts experienced by the miners and the surrounding communities. To take advantage of ASGM as a poverty-alleviating mechanism while reducing unwanted externalities, the cumulative impacts must be understood. Numerous challenges to measuring, monitoring, and addressing ASGM impacts result from the complexity of the impacts themselves, the nature of the gold mining as an informal industry, and the shortfalls in the current regulatory framework. These are discussed in the context of ongoing, unresolved issues including efforts to address trans-boundary water pollution, management of mining waste, and conflicts regarding priorities, ambiguities, and enforcement of existing regulations and policies. Internationally, interventions to address both AGM and SGM impacts have typically focused almost exclusively on technological changes through the elimination of mercury use. Our analysis suggests that to better address ASGM and their cumulative impacts in Ecuador, it will be beneficial to revisit the legal definitions of AGM and SGM. Additionally, promotion of information-based strategies including educational outreach programs and cross-scale and cross-level mitigation methods may also be beneficial. The success of these strategies to reduce ASGM-related cumulative impacts will depend on sufficient funding and the commitment of stakeholders.     

The storage of sewage sludge: influence of liming on the evolution of copper chemical fractions

Sewage sludge re-used in agriculture has to be stabilized and is often stored for several months before land spreading. Stabilization treatment may affect the behaviour of heavy metals such as Cu, which is an element potentially toxic to the environment. In the present study, the chemical forms of copper have been investigated in heaps of limed and unlimed sludge coming from the wastewater treatment plant of Roselies (Belgium). These limed and unlimed aerobically digested sludges were stored during 4 mo in controlled conditions close to field ones. The sequential extraction procedure developed by Tessier was used to determine the copper chemical forms of representative samples taken in the outer shell and in the depth of the heaps. The physico-chemical properties (pH, organic matter, dry matter and temperature) of these samples were also monitored. This study shows that liming transforms part of organically-bound copper into both exchangeable and residual copper. These changes mainly occur during the first 2 wk of storage. After several months of storage, copper passes from the residual fraction to the exchangeable and oxide fractions. During the whole experiment, changes occur faster in the outer shell than in the depth of the heaps. Thus, we demonstrate that the distribution of the copper forms depends on the storage time and it is different in the outer shell from that in the depth of the heaps.     

A study of pedestrian and bicyclist exposure to head injury in passenger car collisions based on accident data and simulations

The objective was to assess head injury risks and kinematics of adult pedestrians and bicyclists in primary impact to the passenger cars and secondary impact to the ground using real world accident data and computer reconstructions of the accidents. For this purpose, a subsample of 402 pedestrians and 940 bicyclists from the GIDAS database, Germany, was used for the statistical analysis, from which 22 pedestrian and 18 bicyclist accidents were further selected for reconstruction. PC-Crash was used to calculate impact conditions, such as vehicle impact velocity, vehicle kinematic sequence, and thrown distance. These conditions were employed to identify the initial conditions in reconstruction in MADYMO program. A comparable analysis was conducted based on the results from accident analysis and computer reconstructions for the impact configurations and the resulting injury patterns of pedestrians and bicyclists in view of head injury risks. Differences in HIC, head-relative impact velocity, linear acceleration, maximum angular velocity and acceleration, contact force, thrown distance, Wrap Around Distance (WAD), and head contact time were evaluated. Injury risk curves were generated by using a logistic regression model for vehicle impact velocity. The results indicate that bicyclists suffered less severe injuries compared with severity of pedestrian injuries. In the selected samples, the AIS 2+ and AIS 3+ head injury risks for pedestrians are 50% probability at impact speed of 38.87 km/h and 54.39 km/h respectively, while for bicyclists at 53.66 km/h and 58.89 km/h respectively. The findings of high injury risks suggested that in the area with high frequency car-pedestrian accidents, the vehicle speed limit should be 40 km/h, while in the area with high frequency car-cyclist accidents the vehicle speed limit should be 50 km/h.     

Functional changes in culturable microbial communities during a co-composting process: Carbon source utilization and co-metabolism

Microbial communities in sewage sludge and green waste co-composting were investigated using culture-dependent methods and community level physiological profiles (CLPP) with Biolog Microplate. Different microbial groups characterized each stage of composting. Bacterial densities were high from beginning to end of composting, whereas actinomycete densities increased only after bio-oxidation phase i.e. after 40 days. Fungal populations become particularly high during the last stage of decomposition. Cluster analyses of metabolic profiles revealed a similar separation between two groups of composts at 67 days for bacteria and fungi. Principal component analysis (PCA) applied to bacterial and fungal CLPP data showed a chronological distribution of composts with two phases. The first one (before 67 days), where the composts were characterized by the rapid decomposition of non-humic biodegradable organic matter, was significantly correlated to the decrease of C, C/N, organic matter (OM), fulvic acid (FA), respiration, cellulase, protease, phenoloxidase, alkaline and acid phosphatases activities. The second phase corresponding to the formation of polycondensed humic-like substances was significantly correlated to humic acid (HA) content, pH and HA/FA. The influent substrates selected on both factorial maps showed that microbial communities could adapt their metabolic capacities to the particular environment. The first phase seems to be focused on easily degradable substrate utilization whereas the maturation phase appears as multiple metabolisms, which induce the release of metabolites and their polymerization leading to humification processes.     

NUMERICAL MODELING OF SOLUTE TRANSPORT PATTERNS IN THE DAMMAM AQUIFER1

ABSTRACT: During the past two decades, the Kingdom of Saudi Arabia has witnessed rapid development in its agricultural and urban areas, which has resulted in greater reliance being placed on its ground water aquifers. The intensive development, particularly along the coastline and in the absence of adequate replenishment sources, has led to major deterioration in the quality and quantity of ground water resources. A numerical model of the Dammam aquifer in the Eastern Province is developed and used to predict the extent of the saline intrusion in the aquifer. The types of stresses effecting the solute transport were identified and remedial measures were suggested. (KEY TERMS: numerical modeling; Saudi Arabia; aquifer; modeling/statistics.)