Nitrogen removal from the saline sludge liquor by electrochemical denitrification

Sludge liquor from the sludge dewatering process has a high ammonia content. In the present study, a lab-scale electrochemical (EC) system with a pair of Ti electrode plates was used for treating the sludge centrate liquor of digested wastewater sludge with a NH4 + - N content of around 500 mg/L. The sludge liquor had a high salinity due to seawater being used for toilet flushing in Hong Kong. The results show that the EC process is highly effective for denitrification of the saline sludge liquor. Complete nitroger removal could be achieved within 1 hr or so. The rate of EC denitrification increased with the current intensity applied. The best current efficiency for nitrogen removal was obtained for a gap distance between the electrodes at 8 mm. Electro-chlorination was considered to be the major mechanism of EC denitrification. The formation of chlorination by-products (CBPs) appeared to be minimal with the total trihalomethanes (THM) detected at a level of 300 μg/L or lower. The power consumption for EC denitrification was around 23 kWh/kg N. Additional electro-flocculation with a pair of iron needle electrodes could enhance the flocculation and subsequent sedimentation of colloidal organics in the sludge liquor, increasing the organic removal from less than 30% to more than 70%. Therefore, the EC process including both electro-denitrification and electro-flocculation can be developed as the most cost-effective method for treatment of the saline sludqe liquor. © IWA Publishing 2006.postprin

Characterization of soluble microbial products as precursors of disinfection byproducts in drinking water supply

Water pollution by wastewater discharge can cause the problem of disinfection byproducts (DBPs) in drinking water supply. In this study, DBP formation characteristics of soluble microbial products (SMPs) as the main products of wastewater organic biodegradation were investigated. The results show that SMPs can act as DBP precursors in simulated wastewater biodegradation process. Under the experimental conditions, stabilized SMPs had DBPFP (DBP formation potential) yield of around 5.6 mumol mmol(-1)-DOC (dissolved organic carbon) and DBP speciation profile different from that of the conventional precursor, natural organic matter (NOM). SMPs contained polysaccharides, proteins, and humic-like substances, and the latter two groups can act as reactive DBP precursors. SMP fraction with molecular weight of <1 kDa accounted for 85% of the organic carbon and 65% of the DBP formation. As small SMP molecules are more difficult to remove by conventional water treatment processes, more efforts are needed to control wastewater-derived DBP problem in water resource management.postprin

Reaction pathways and mechanisms of the electrochemical degradation of phenol on different electrodes

Laboratory experiments were carried out on the kinetics and pathways of the electrochemical (EC) degradation of phenol at three different types of anodes, Ti/SnO2-Sb, Ti/RuO2, and Pt. Although phenol was oxidised by all of the anodes at a current density of 20 mA/cm2 or a cell voltage of 4.6 V, there was a considerable difference between the three anode types in the effectiveness and performance of EC organic degradation. Phenol was readily mineralized at the Ti/SnO2-Sb anode, but its degradation was much slower at the Ti/RuO2 and Pt anodes. The analytical results of high-performance liquid chromatography (HPLC) and gas chromatography coupled with mass spectrometry (GC/MS) indicated that the intermediate products of EC phenol degradation, including benzoquinone and organic acids, were subsequently oxidised rapidly by the Ti/SnO2-Sb anode, but accumulated in the cells of Ti/RuO2 and Pt. There was also a formation of dark-coloured polymeric compounds and precipitates in the solutions electrolyzed by the Ti/RuO2 and Pt anodes, which was not observed for the Ti/SnO 2-Sb cells. It is argued that anodic property not only affects the reaction kinetics of various steps of EC organic oxidation, but also alters the pathway of phenol electrolysis. Favourable surface treatment, such as the SnO2-Sb coating, provides the anode with an apparent catalytic function for rapid organic oxidation that is probably brought about by hydroxyl radicals generated from anodic water electrolysis. © 2005 Elsevier Ltd. All rights reserved.postprin

The association of up-regulation of FGF3 and hepatocellular carcinoma metastasis and recurrence

published_or_final_versio

Loss of tyrosine aminotransferase may contribute to the pathogenesis of hepatocellular carcinoma

Program no. 509postprin

A numerical study of the impact of climate and emission changes on surface ozone over South China in Autumn time in 2000-2050

2012-2013 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Effect of exogenous methyl jasmonate on growth, gas exchange and chlorophyll contents of soybean subjected to drought

Drought is considered as one of the major constraints to crop production worldwide. Methyl jasmonate (MJ) is a plant-signaling molecule that elicits a wide variety of plant responses ranging from morphological to molecular level. A pot-culture study was undertaken to investigate the possible role of MJ-treatment on growth, gas exchange and chlorophyll contents in soybean (Glycine max L. Merrill.) plants subjected to water stress. The soybean plants were grown under normal water supply conditions till blooming and were then subjected to moisture stress by withholding water followed by foliar application of MJ at the rate of 50 μM. Drought stress severely hampered the growth, leaf gas-exchange attributes as well as the photosynthetic pigment contents. It was evident from the experimental results that, MJ-treatment led to further impairment in growth by inhibiting the leaf gas exchange attributes and chlorophyll contents. It is worth noted that, MJ-treatment also hampered the performance of soybean crop under well-watered conditions. In all, MJ-treatment appeared to arrest the growth, impaired leaf gas-exchange attributes and caused the loss of chlorophyll contents of soybean plants under water deficit conditions.Key words: Chlorophyll contents, drought stress, growth, gas exchange, soybean (Glycine max L. Merrill.)

The association of cytoplasmic overexpression of cyclin d1 and tumor metastasis in Hepatocellular Carcinoma

published_or_final_versio

Heterogenous expression of beta-catenin, p16, e-cadherin, and c-myc in multi-stage colorectal carcinogenesis detected by tissue microarray

published_or_final_versio

Preparation and analysis of a new bioorganic metallic material

Biofouling on metal surfaces is one of the main reasons for increased ship drag. Many methods have already been used to reduce or remove it with moderate success. In this study, a synthetic peptide has been utilized to react with 304 stainless steel aiming to generate a bioorganic stainless steel using a facile technique. After the reaction, white matter was found on the surface of the treated stainless steel via SEM, whilst the nontreated stainless steel had none. Elemental analysis confirmed that excessive N existed on the surface of the treated samples using an integrated SEM-EDS instrument, implying the presence of peptides binding on the surface of the bioorganic stainless steel. The FTIR spectra showed amide A and II peaks on the surface of the bioorganic stainless steel suggesting that either the peptides grafted onto the steel surface or the polypeptide composition accumulated on the steel samples. XPS analysis of the treated steel demonstrated that there was nitrogen bonding on the surface and it was a chemical bond via a previously unreported chemical interaction. The treated steel has a markedly increased contact angle (water contact angle of 65.7 ± 4.7° for nontreated steel in comparison to treated, 96.4 ± 2.1°), which supported the observation of the wettability change of the surface, i.e. the decrease of the surface energy value after peptide treatment. The changes of the surface parameters (such as, Sa, Sq, Ssk and Sku) of the treated steel by surface analysis were observed