A pilot-scale microfiltration polyvinylidene fluoride (PVDF) membrane with multiple pore sizes (0.1 μm and 0.05 μm) was operated after a coagulation/sedimentation using a polysilicato iron (PSI) as coagulant has been fabricated and operated. As a result, turbidity was removed completely and organic matter, humic substances, and metals (Al, Fe) were removed very well by the experimental system. Accordingly, it was concluded that a membrane with a dense skin was more effective for reducing membrane fouling than a membrane with homogeneous structure although the nominal pore size of the former (0.05 μm) was smaller than that of the latter (0.1 μm). It still remains to study the effects on membrane fouling of the interaction between organic and oxidized inorganic matters (such as Fe and Mn) which occure during pre-chlorination.
The objective of this study is to identify the characteristics of SS and nitrate removal using hybrid sludge bed filter and combined with electrode system for advanced treatment of secondary clarifier effluents. The following results were obtained. The hybrid filter could remove SS and nitrate simultaneously. Larger particles than about 5 μm in diameter were removed completely at filtration rate 15 m·d-1 and sludge bed thickness 20cm. The head loss of the filter was less than 0.34 m of water at the highest value. The denitrification rate by the bio-electrochemical process was estimated to be around 0.036 kg-N·kg-SS-1·day-1 at the applied electric current density, 0.76 mA·cm-2 and the endogenous denitrification rate in the subsided sludge bed was 0.0052 kg-N·kg-SS-1·day-1. The nitrate removal rate was enriched by the bio-electrochemical reaction. The hybrid filter may be substituted for conventional granular bed and bio-filters from not only the SS removal point of view but also nitrate removal point of view.
Surface transfer and bubble transfer both contribute significantly to oxygen transfer in a conventional aeration system. However, bubble transfer plays the primary role of oxygen transfer. In the present study, the mere surface transfer is replaced by directly contacting liquid film designed elegantly with air. Liquid film aeration system is successfully developed on a laboratory scale. The experimental results from single-pass aeration mode show that the dissolved oxygen concentration in deoxygenate water reaches up to 95 % or higher, as compared with the saturation concentrations of the dissolved oxygen while using this novel aeration system. Meanwhile, an increase in oxygen mass transfer rate by 30% can be achieved in comparison with conventional aeration system. Moreover, the volumetric mass transfer coefficient for liquid film-forming apparatus (KLal) is found to be as much as 5 times higher than that for water surface in a conventional aeration test.
The objective of this study was to clarify the effect of different adsorption/desorption properties and biodegradability of chemicals on the performance of powdered activated carbon (PACT) processes. The higher performance was observed in the PACT process than the activated sludge process for the substances with high adsorbability (3,5-DCP and 3-BP). Biodegradation occurred continuously after shock loading for substances with desorbability and biodegradability (3-BP and BAA). Due to the continuous degradation of desorbed substance after shock loading, total amount of substance removed by biodegradation in the PACT process was larger than the activated sludge process for the substances with high adsorbability, desorbability and biodegradability (3-BP).
Two pilot-scale polyvinylidene fluoride (PVDF) microfiltration (MF) membranes with different structures (i.e. symmetric and asymmetric) were operated after coagulation/sedimentation, sand filtration, and chlorination. Turbidity was removed completely. Moreover, humic substances, Al, and Fe were removed very well by the pilot-scale system. An asymmetric membrane (HFS membrane) having a nominal pore size of 0.05 μm showed relatively high removal efficiency of the small organic matter (about 6,000 Da) than a symmetric membrane (HFM membrane) having a nominal pore size of 0.1 μm. However, the extracted inorganic concentrations of the HFM membrane were relatively higher than that of the HFS membrane. Therefore, it could be concluded that the HFS membrane better reduced membrane fouling than the HFM although the nominal pore size of the former was half of the latter. To control microbial growth and mitigate membrane fouling, a NaOCl solution was injected into the effluent of sand filtration before the both membranes. However, it adversly affected membrane fouling due to the oxidization of inorganic substances such as Al, Fe, and Mn.
The objective of this paper is to identify the source and transport of nitrate in the groundwater aquifers of alluvial fans by stable isotopic techniques. Water samples collected from the precipitation, groundwater, and river water at the western Kofu basin were analysed for the major cations, anions, and isotopes (δ18O and δ15N). Through the cluster analysis of the cations and anions, two groundwater aquifers formed on the Midai and Kamanashi alluvial fans were identified in the basin. Higher nitrate concentrations were observed in the groundwater aquifers of the Midai alluvial fan, and the values of δ15N suggest that the major sources of nitrate are the inorganic and organic fertilizers applied in the orchards and paddy fields. The values of δ18O show that precipitation and river water are sources of recharge in both the aquifers. A strong positive correlation between the nitrate concentration and the δ18O values of both the groundwater aquifers shows that precipitation water acts as a carrier and river water facilitates dilution in the nitrate loading from terrestrial catchments.
It is indeed important to monitor water quality in water-resource and raw water for water system entity. In particular, urgent response is required for sudden water pollution, therefore many water system entities put weight heavily on corresponding counterapproaches. Various counterapproaches are employed such as automatic fish monitoring system, oil film detector, oil content detector, full-automatic cyanogens analyzer, monitoring Volatile Organic Compounds (VOC) by using gas chromatograph, and monitoring hazardous material using UV measuring device since it is significantly important to keep damage to the minimum. Among these sudden water pollution incidents, incident caused with oil could be the worst and devastative. If oil reaches to the core of water utility especially distributing reservoir, it will be harder to respond to such incident For this reason, this report states an oil counterapproach implemented by Hiroshima city as an example this time.
The effect of coagulation and ozonation as pretreatments for granular activated carbon (GAC) filtration on calcium accumulation onto GAC was studied. Three kinds of FA solutions extracted from commercial leaf mold for horticulture were used: FA itself, FA after coagulation (FA-c) and FA after ozonation (FA-oz). Coagulation used as pretreatment before GAC filtration significantly decreased calcium accumulation onto GAC while ozonation caused a small increase on calcium accumulation onto GAC. Acidic functional groups into GAC introduced by adsorption of fulvic acid controlled accumulation of calcium onto GAC. Significant decrease of calcium accumulation onto GAC by coagulation was caused by the removal of the fraction with acidic functional groups from FA.