Atmospheric concentrations of aluminium, an indicator of dust substances, have been determined in a set of high‐volume aerosol particle samples collected at different locations over continental China and over the China Sea. High concentrations of dust were observed in northern continental China, and at certain locations such as Beijing dust may include an anthropogenic fraction. The mass particle‐size distributions of dust varied depending on its distance from source regions, with the mass median diameter for Al of ˜1.6‐5.9 µm at Beijing in northern China and ˜ 1.9 µm over off‐shore areas of the East China Sea. Model‐predicted mean dry deposition velocities of dust particles are from 1.4 to 4.8 cm s−1 over northern continental China and from 1.4 to 2.1 cm s−1 over the China Sea. Atmospheric deposition models have been applied to estimate the atmospheric fluxes and deposition of dust at different locations. The estimated atmospheric flux of dust at X''an of the Loess Plateau is 25 (4.9 to 44) g m−2 mo−1 which is the highest among the regions we studied. The estimated present‐day dust flux is comparable to the late quaternary records of eolian dust accumulation at this site. The total atmospheric deposition of dust to the China Sea is 67 Tg yr−1, accounting for 14% of the total atmospheric deposition of dust to the entire North Pacific. With such a high deposition rate, Asian dust may play an important rôle in biogeochemical cycles of trace substances in the Asia/North Pacific region.
The impact of adding a modified Ludzack–Ettinger (MLE) configuration with Nitrate Recycle (NRCY) on continuous-flow aerobic granulation has yet to be explored. The potential negative effects of MLE on sludge densification include that: (1) bioflocs brought by NRCY could compete with granules in feast zones; and (2) carbon addition to anoxic zones could increase the system organic loading rates and lead to higher feast-to-famine ratios. Two pilot-scale plug flow reactor (PFR) systems fed with real domestic wastewater were set up onsite to test these hypotheses. The results showed that MLE configuration with NRCY could hinder the sludge granulation, but the hindrance could be alleviated by the NRCY location change which to some extent also compensates for the negative effect of higher feast-to-famine ratios due to carbon addition in MLE. This NRCY location change can be advantageous to drive sludge densification without a radical washout of the sludge inventory, and had no effects on the chemical oxygen demand (COD) and nitrogen removal efficiencies. The PFR pilot design for the MLE process with a modified NRCY location tested in this study could be developed as an alternative to hydrocyclones for full-scale, greenfield, continuous sludge densification applications.
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