A huge accumulation of domestic waste has caused serious environmental contamination in rural areas of developing countries (RADIC). The characteristics and management of domestic waste are carefully discussed, based on field surveys and a literature review. The results indicate that the generation in most of RADIC is less than the median of 0.521 kg day−1 per capita in China, and much smaller than in rural areas of developed countries (RADEC). Organic waste and inert waste with an accumulative mass percentage of 72.31% are dominant components of domestic waste in the rural areas of China. There are trends of increasing amounts of kitchen waste, paper/cardboard, and plastic/rubber and a decreasing trend of ash waste. The RADIC composition of domestic waste had a high content of organic waste and a low content of recyclable waste compared to the RADEC. Domestic waste has good compressibility and a light bulk density ranging from 40 to 650 kg m−3. The moisture, ash, combustible, and calorific values of domestic waste were 53.31%, 18.03%, 28.67%, and 5368 kJ kg−1, respectively. The domestic waste has an abundance of nutrients including organic matter (39.05%), nitrogen (1.02%), phosphorus (0.50%), and potassium (1.42%). In RADIC, domestic waste can be used as an agricultural manure only after it has been collected and sorted for the potential risk of heavy metal accumulation. Based on these characteristics of domestic waste and the different situations of rural areas, four waste management modes including centralized treatment, decentralized treatment, group treatment, and mobile treatment are designed and discussed.
Aerobic biodegradation of decabromodiphenyl ether (PBDE-209) by Pseudomonas aeruginosa under the influence of co-metabolic substrates and heavy metal cadmium ion was studied, The results showed that certain amount of co-metabolic substrates, such as glucose, sucrose, lactose, starch, and beef extract, would promote the biodegradation of PBDE-209, among which glucose most favorably accelerated PBDE-209 degradation by about 36% within 5 d. The highest degradation efficiency was reached at the ratio of PBDE-209 and glucose 1:5 while excessive carbon source would actually hamper the degradation efficiency. Exploration of influences of cadmium ion on PBDE-209 biodegradation indicated that degradation efficiency was stimulated at low concentrations of Cd2+ (0.5–2 mg L−1) while inhibited at higher levels (5–10 mg L−1), inferring that the heavy metals of different concentrations possessed mixed reactions on PBDE-209 bioremoval. Bromine ion was produced during the biotransformation process and its concentration had a good negative correlation with the residues of PBDE-209. Two nonabromodiphenyl ethers (PBDE-208, PBDE-207), four octabromodiphenyl ethers (PBDE-203, PBDE-202, PBDE-197, PBDE-196) and one heptabromodiphenyl ethers (PBDE-183) were formed with the decomposition of PBDE-209, demonstrating that the main aerobic transformation mechanism of PBDE-209 was debromination. 相似文献
Waste sulfuric acid is a byproduct generated from numerous industrial chemical processes. It is essential to remove the impurities and recover the sulfuric acid from the waste acid. In this study the rectification method was introduced to recover high purity sulfuric acid from the waste acid generated in toluene nitration process by using rectification column. The waste acid quality before and after rectification were evaluated using UV–Vis spectroscopy, GC/MS, HPLC and other physical and chemical analysis. It was shown that five nitro aromatic compounds in the waste acid were substantially removed and high purity sulfuric acid was also recovered in the rectification process at the same time. The COD was removed by 94% and the chrominance was reduced from 1000° to 1°. The recovered sulfuric acid with the concentration reaching 98.2 wt% had a comparable quality with commercial sulfuric acid and could be recycled back into the toluene nitration process, which could avoid waste of resources and reduce the environmental impact and pollution. 相似文献
Simazine sorption to corn straw biochars prepared at various temperatures (100-600 °C) was examined to understand its sorption behavior as influenced by characteristics of biochars. Biochars were characterized via elemental analysis, BET-N2 surface area (SA), FTIR and 13C NMR. Freundlich and dual-mode models described sorption isotherms well. Positive correlation between log Koc values and aromatic C contents and negative correlation between log Koc values and (O + N)/C ratios indicate aromatic-rich biochars have high binding affinity to simazine (charge transfer (π-π*) interactions) and hydrophobic binding may overwhelm H-bonding, respectively. Dual-mode model results suggest adsorption contribution to total sorption increases with carbonization degree. Positive correlation between amounts of adsorption (Qad) and SA indicates pore-filling mechanism. Comparison between our results and those obtained with other sorbents indicates corn straw biochars produced at higher temperature can effectively retain simazine. These observations will be helpful for designing biochars as engineered sorbents to remove triazine herbicides. 相似文献
This paper investigates the influence of near-bank vegetation patches on the bed morphological adjustment in open channel flow systems. The 2D depth-averaged hydro-morphological model is adopted for this investigation, which is first validated by laboratory experimental data measured in an open channel with a single near-bank vegetation patch. The validated model is then applied for extensive numerical simulations, with the aim of conducting a systematic analysis of the influence of different geometric controlling parameters on the bed morphological evolution. The controlling parameters taken into account for numerical analysis include the angle of repose value (RAV) of sediment, vegetation density (VD), patch length (PL) and patch width (PW). The numerical results and analysis show that: (1) the RAV of sediment with slope-failure parametrization only influences the shape of the transverse bed topography in the junction region; (2) increase in VD, PL and PW that substantially enhances flow blockage effect encourages the growth of the pool adjacent to the patch in three dimensions; (3) increase in VD, PL and PW produces analogous retrogressive erosion (erosion toward the upstream) in the pool region, presumably due to the increase in flow resistance. Additional numerical experiments suggest that the staggered-order distribution of multiple patches might be an optimal choice for channel restoration and conservation since pools and riffles with larger scales can be produced.