Yuanfeng Qi

Preparation and mechanism of ultra-lightweight ceramics produced from sewage sludge

The preparation, characterization, preheating mechanism and bloating mechanism of ultra-lightweight ceramics (ULWC) manufactured by dehydrated sewage sludge (DSS) and clay were studied. Three experiments were designed to investigate the addition of DSS, the effect of preheating treatment and sintering treatment, respectively, and then the optimum conditions for preparing ULWC were determined. Chemical components, especially ratios of carbon content to iron oxide content (C/Fe-ratios), were used to explain the preheating mechanism; physical forces (surface tension and bloating force) combined with C/Fe-ratios were used to explain the bloating mechanism. The characterizations (physical properties, microstructure properties and toxic metal leaching properties) of ULWC that were prepared under the optimum conditions were tested. The results showed that the optimum addition of DSS was 20-30 wt.%, and the pellets which preheated at 400 degrees C for 20 min and sintered at 1150 degrees C for 10 min were beneficial to produce ULWC. Property tests of ULWC showed that ULWC was light (with a bulk density of 330.80 kg m(-3)), waterproof (with a water absorption of 5.30 wt.%), nontoxic (contents of toxic metal leaching test were all below the detection limit) and suitable for practical civil engineering.

Research on the characteristics of red mud granular adsorbents (RMGA) for phosphate removal.

Red mud (RM), a waste tailing from alumina industry, was employed with bentonite and starch as the main raw materials for producing granular adsorbents in this study. The important parameters, which greatly affect the characteristics of red mud granular adsorbents (RMGA), such as the mass ratio of three raw materials, preheating time, preheating temperature, sintering time and sintering temperature (ST), were investigated. Adsorption capacities for various RMGA were described in terms of removal of phosphate from aqueous solution according to the adsorption experiments, in which certain operation parameters (like stirring speed, reaction time, adsorbent dosage, initial pH and initial phosphate concentration) at three different aquatic temperatures (AT) were applied. The results showed that the optimum ST, under which the largest adsorption capacity was achieved for RMGA with certain RM ratio, varied with different AT in adsorption process. Based on the further characterizations of RMGA, it was speculated that the performance above was caused by the competitive interactions of chemical adsorption and physical adsorption on RMGA, since the increase in ST could lead to qualitative diversification on the surface and quantitative decrease of effective components for adsorption simultaneously.

Preparation of ultra-lightweight sludge ceramics (ULSC) and application for pharmaceutical advanced wastewater treatment in a biological aerobic filter (BAF)

Novel media-ultra-lightweight sludge ceramics (ULSC) employed in an upflow lab-scale biological aerobic filter (BAF) were investigated for pharmaceutical advanced wastewater treatment. The influences of the volume ratio of pharmaceutical wastewater to domestic wastewater (PW/DW), hydraulic retention time (HRT) and air-liquid ratio (A/L) on chemical oxygen demand (CODCr) and ammonium (NH(4)(+)-N) of the effluent were investigated. When PW/DW of 4:1, HRT of 6 h, and A/L of 5:1 were applied, the mean effluent concentration of NH(4)(+)-N was 6.2 mg L(-1), and the maximum CODCr concentration in the effluent was 96 mg L(-1). Both NH(4)(+)-N and CODCr did not exceed the limits of the national discharge standards (NH(4)(+)-N ≤ 15 mg L(-1), CODCr ≤ 100 mg L(-1)). In addition, the BAF system showed a strong capacity of further removal from NH(4)(+)-N of the effluent.

The characteristics and application of sludge-fly ash ceramic particles (SFCP) as novel filter media

Novel filter media-sludge-fly ash ceramic particles (SFCP) were prepared using dewatered sludge, fly ash and clay with a mass ratio of 1:1:1. Compared with commercial ceramic particles (CCP), SFCP had higher total porosity, larger total surface area and lower bulk and apparent density. Tests of heavy metal elements in lixivium proved that SFCP were safe for wastewater treatment. A lab-scale upflow anaerobic bioreactor was employed to ascertain the application of SFCP in denitrification process using acetate as carbon source. The results showed that SFCP reactor brought a relative superiority to CCP reactor in terms of total nitrogen (TN) removal at the optimum C/N ratio of 4.03 when volumetric loading rates (VLR) ranged from 0.33 to 3.69 kg TN (m(3)d)(-1). Therefore, SFCP application, as a novel process of treating wastes with wastes, provided a promising way in sludge and fly ash utilization.

Preparation of ceramic-corrosion-cell fillers and application for cyclohexanone industry wastewater treatment in electrobath reactor.

As new media, ceramic-corrosion-cell fillers (Cathode Ceramic-corrosion-cell Fillers - CCF, and Anode Ceramic-corrosion-cell Fillers - ACF) employed in electrobath were investigated for cyclohexanone industry wastewater treatment. 60.0 wt% of dried sewage sludge and 40.0 wt% of clay, 40.0 wt% of scrap iron and 60.0 wt% of clay were utilized as raw materials for the preparation of raw CCF and ACF, respectively. The raw CCF and ACF were respectively sintered at 400°C for 20 min in anoxic conditions. The physical properties (bulk density, grain density and water absorption), structural and morphological characters and toxic metal leaching contents were tested. The influences of pH, hydraulic retention time (HRT) and the media height on removal of COD(Cr) and cyclohexanone were studied. The results showed that the bulk density and grain density of CCF and ACF were 869.0 kg m(-3) and 936.3 kg m(-3), 1245.0 kg m(-3) and 1420.0 kg m(-3), respectively. The contents of toxic metal (Cu, Zn, Cd, Pb, Cr, Ba, Ni and As) were all below the detection limit. When pH of 3-4, HRT of 6h and the media height of 60 cm were applied, about 90% of COD(cr) and cyclohexanone were removed.

The performance of biological anaerobic filters packed with sludge-fly ash ceramic particles (SFCP) and commercial ceramic particles (CCP) during the restart period: effect of the C/N ratios and filter media.

Two lab-scale upflow biological anaerobic filters (BAF) packed with sludge-fly ash ceramic particles (SFCP) and commercial ceramic particles (CCP) were employed to investigate effects of the C/N ratios and filter media on the BAF performance during the restart period. The results indicated that BAF could be restarted normally after one-month cease. The C/N ratio of 4.0 was the thresholds of nitrate removal and nitrite accumulation. TN removal and phosphate uptake reached the maximum value at the same C/N ratio of 5.5. Ammonia formation was also found and excreted a negative influence on TN removal, especially when higher C/N ratios were applied. Nutrients were mainly degraded within the height of 25 cm from the bottom. In addition, SFCP, as novel filter media manufactured by wastes-dewatered sludge and fly ash, represented a better potential in inhibiting nitrite accumulation, TN removal and phosphate uptake due to their special characteristics in comparison with CCP.

Characteristics and trihalomethane formation reactivity of dissolved organic matter in effluents from membrane bioreactors with and without filamentous bulking.

In this study, synthetic wastewater was treated by two identical membrane bioreactors (MBRs): the normal sludge MBR (NS-MBR) and the bulking sludge MBR (BS-MBR). Effects of filamentous bulking on the characteristics and trihalomethane (THM) formation reactivity of MBR effluent dissolved organic matter (EfOM) were investigated. Filamentous sludge bulking had no significant influence on the regulated MBR effluent water quality except NO2-N and NO3-N. NS-MBR effluent had more low molecular weight (LMW) (<5kDa) EfOM (92.43%) than BS-MBR (75.18%). About two-thirds of EfOM from BS-MBR were hydrophilic substances. On the contrary, EfOM from NS-MBR exhibited higher hydrophobicity. The ratio of polysaccharides and proteins in MBR effluents increased after filamentous bulking. There were more protein-like materials, fulvic acid-like and humic acid-like in BS-MBR EfOM. The THM formation reactivity of BS-MBR EfOM was 30.15% of NS-MBR EfOM, whereas BS-MBR EfOM exhibited higher formation reactivity of bromine containing species.

Preparation of paper mill sludge-based granular activated carbon fillers for fluidized-bed bioreactor (FBBR).

Paper mill sludge (PMS) was utilized to prepare granular activated carbon (GAC) fillers for fluidized-bed bioreactor (FBBR) through stream activation. The properties of the PMS were tested and the optimum conditions for the production process were determined. Then, the GAC fillers were used in the FBBR to investigate the capacity for wastewater treatment. The results showed that the optimal conditions were: carbonization temperature of 450 °C, carbonization time of 50 min, activation temperature of 800 °C and activation time of 60 min. The specific surface area of the GAC fillers was 130 m2/g and the grain density was 1.34×103 kg/m3. The wastewater treatment results showed that after 40 days of running, under the conditions of influent COD of 800 mg/L and HRT of 2 h, the COD removal efficiency was about 90%, which demonstrated that PMS-based GAC fillers were feasible for FBBR.

Properties and effect of forming sewage sludge into lightweight ceramics

In this work we investigated the chemical, thermal and toxic properties of dried sewage sludge (DSS), the preparation and properties of lightweight sludge ceramic (LSC) and the mechanisms of action of the organic and inorganic foaming agents (OFAs and IFAs). The chemical components and thermal properties of the raw materials were studied by Energy Dispersive X-ray Detection (EDX) and Thermogravimetric Analysis and Differential Scanning Calorimetry (DSC/TGA). The mineral phases of the raw materials and the formed ceramics were determined by X-ray Diffraction (XRD). The leaching characteristics of heavy metals were investigated with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Different ratios of DSS and clay were mixed and pressed into raw pellets. After drying and preheating treatment, the raw pellets were sintered at 1150°C for 10 min. The physical properties of LSC (50 wt% DSS added) were tested. The results showed that when the addition of DSS was above 50 wt%, LSC began to shrink, and a maximum density occurred. The environmental safety of LSC was satisfactory. XRD showed that some new mineral phases formed in the LSC. Observation of the microstructure by Scanning Electron Microscope (SEM) indicated that the body of LSC was porous.

Preparation and Properties of Sewage Sludge Ceramic Pellets

The object of this study is to investigate the sintering processes of sewage sludge ceramic pellets (SSCP) as filter media. The effects of adding coal fly ash and farmland clay were tested, and the feasibility of using SSCPs in a biological aerated filter (BAF) was determined by comparing their performance with that of commercial ceramic pellets (CCP). Unlike the procedure to make lightweight sewage sludge aggregates as construction material, the sintering techniques for formation of the SSCP filter material were as follows: a maximum mass ratio of 35% dried sewage sludge mixed with clay and fly ash was preheated at 400&#8451; for 20 min, then sintered at 1000&#8451; to 1050&#8451; for 5-10 min. The main chemical composition of SSCP and CCP was similar, and the environmental suitability of SSCP is satisfactory. Scanning electron microscopy images showed that the dimensions of the pores on the surface and interior of SSCP were much larger than those of CCP. Removal of NH3-N in BAFs filled with SSCP as carrier was higher about 10% than with CCP, which indicated that SSCP supplied a much better environment for the nitrifying and denitrifying bacteria.