Applying chemical sedimentation process in drinking water treatment plant to address the emergent arsenic spills in water sources

Arsenic （As） spills and sometimes polluted water occurred more frequently sources in recent years in China. It is as urgent need to develop emergency treatment technologies to address the arsenic threat for large-scale water treatment plants. In response, we developed a chemical sedimentation technology to remove arsenic contaminants for water treatment plants. Bench-scale experiments were conducted to investigate the efficiency of arsenic removal and the influencing factors of the chemical sedimentation treatment process. The influencing factors included the choice and dosage of coagulants, the valence of arsenic and pH value of solution. The As（V） contaminants can be almost completely removed by ferric or alum coagulants. The As（III） contaminants are more recalcitrant to chemical sedimentation, 75% for ferric coagulant and 40% for alum coagulant. The quantitative results of arsenic removal load by different ferric or alum coagulants were presented to help determine the parameters for arsenic treatment technology. The dominant mechanism for arsenic removal is static combination, or adsorption of negative arsenic species onto positive ferric hydroxide or alum hydroxide flocs. The efficiency of this treatment technology has also been demonstrated by a real production test in one water treatment plant with arsenicrich source water and one emergency response. This technology was verified to be quick to set-up, easy to operate and highly efficient even for high concentration of arsenic.

A study on chemical forms of heavy metals in the sediments of Zhujiang River and its estuary

The five chemical bound forms of Fe, Al and Mn in sediments in the main channel of the Zhujiang River.and its estuary, namely, exchangeable, carbonic, oxidative, organic and residual (in crystal) forms, were determined. The method of sequential extraction was used for separating the five bound forms.The main chemical form of the three elements in the sediments of the Zhujiang River and its estuarine zone is the residual one. The exchangeable form exists only in a small fraction.Correlationships between the concentration of a certain form of heavy metals and Eh. pH and salinity were discussed. The principles of geochemistry are used to explain the mechanism of heavy metal transport in the river.It was also found that the distribution rule of the chemical forms of Fe, Al and Mn in sediments in the lower reaches of the Zhujiang River was similar to the one in the lower reaches of the Yamaska River.

Subaerial hot springs and near-surface hydrothermal mineral systems past and present,and possible extraterrestrial analogues

The principal features,geotectonic settings and association with near-surface hydrothermal mineral systems of ancient and present subaerial hot springs,fumaroles and geysers are herein reviewed.Fumaroles and geysers usually occur in volcanic craters and are in most cases,part and parcel of hot spring environments.Subaerial hot springs are characterised by siliceous-and carbonate-rich chemical sediments,such as sinters and travertines,respectively.Sinters are commonly enriched in various metalliferous elements.Hot springs surface discharges are also characterised by pools,which exhibit bright colours due to the presence of microorganisms.Present-day examples discussed in this paper,include the fumaroles and hot springs of the White Island volcano(New Zealand),the world-renowned Yellowstone caldera(USA)and the Afar region of the East African Rift System.The Afar triangle,in the northern part of East African Rift System,provides a good example of hot springs associated with evaporative deposits.The Tuli-Sabi-Lebombo triple junction rifts were formed during the^180 Ma Karoo igneous event in southern Africa,of which the Tuli arm is the failed rift(aulacogen),as is the Afar region.The Tuli rift is effectively an unusual,if not unique,tectono-thermal setting,because it comprises Karoo-age hot springs systems and associated vein stockworks and breccias,which includes the Messina Cu deposit as well as currently active hot springs with sinter deposits probably due to post-Karoo uplift.Fumarolic pipes in ignimbrites of the Erongo Volcano-Plutonic Complex in Namibia are discussed.This is followed by an example of banded chert rocks in the Killara Formation of the Palaeoproterozoic Capricorn Orogen(Western Australia),interpreted as hot spring chemical sediments,which also show evidence of"fossil"microbial filaments.The paper ends with a brief overview of possible analogues of hot springs on planet Mars.

Sedimentation in a Continental High-Frequency Oscillatory Lake in an Arid Climatic Background:A Case Study of the Lower Eocene in the Dongying Depression,China

The sedimentary environment, formation conditions, sedimentary characteristics and the basin evolution model of high-frequency oscillatory lake in arid climatic background of the Lower Eocene in the Dongying depression were studied through the analysis of drilling cores, sporepollen, geochemistry and geophysics data. During the sedimentary period of the Eocene Ek^3-Es^4x formations, because of the frequent alternation between dry and wet climates in the arid climatic background and the gentle paleo- geomorphology, the lake level and salinity of the Early Eocene Dongying depression frequently and rap- idly increased and decreased, which is referred to as a high-frequency oscillatory lake. The sedimentation and distribution of sediments in this high-frequency oscillatory lake basin were controlled by the fre- quently alternating dry-wet climates. During periods with relatively wet climate, the seasonal floods and unstable rivers led to the formation of over-flooding lake deltas in the gentle slope belt, and fine-grained clastic sediments, with minor thin layers of gypsum-salt rocks in the sag belt. During the relatively arid climatic periods, sedimentation occurred mainly in the limited area of the sag belt with thick gypsum-salt rocks. Because of the impact of the salinity stratification of the lake water, these gypsum-salt rocks exhibit annular structural features. A sedimentary cycle of the oscillatory lake began with isochronous flood channels and ended with relatively thick gypsum rocks and salt rocks. The thickness of one oscillatory cy- cle is generally 4-20 m. The superposition of multiple sedimentary cycles of the oscillatory lake constitutes the overall vertical idling sequence of the high-frequency oscillatory lake basin.

Acidogenic sludge fermentation to recover soluble organics as the carbon source for denitrification in wastewater treatment： Comparison of sludge types

For biological nitrogen （N） removal from wastewater, a sufficient organic carbon source is requested fbr denitrification. However. the organic carbon/nitrogen ratio in municipal wastcwatcr is becoming lower in recent years, which increases the demand for the addition of external organic carbon, e.g. methanol, in wastewater treatment. The volatile fatty acids （VFAs） produced by acidogenic fenncntation of sewage sludge can be an attractive alternative for methanol. Chemically enhanced primary sedimentation （CEPS} is an effective process that applies chemical coagulants to enhance the removal of organic pollutants and phosphorus from wastewater by sedimentation. In temls of the chemical and biological characteristics, the CEPS sludge is considerably different from the conventional primary and secondary sludge. In the present study, FeCI3 and PACI （polyalunfinum chloride） were used as the coagulants for CEPS treatment of raw sewage. The derived CEPS sludge （Fe-sludge and Al-sludge） was then processed with mcsophilic acidogenic fennentation to hydrolysc the solid organics and produce VFAs for organic carbon recovery, and the sludge acidogenesis efficiency was compared with that of the conventional primary sludge and secondary sludge. The results showed that the Fe-sludge exhibited the highest hydrolysis and acidogenesis efficiency, while the Al-sludge and secondary＇ sludge had lower hydrolysis efficiency than that of primary sludge. Utilizing ffie Fc-sludgc fermentation liquid as tbc carbon source for denitrificatiom more than 99%of nitrate removal was achieved in the main-stream wastewater treatment without any external carbon addition, instead of 35% obtained from the conventional process of primary sedimentation followed by the oxic/anoxic （O/A） treatment.