Ceramic Candle Filter Research Articles

Efficiency of Ceramic Candle Filters towards Purification of Drinking Water

Efficiency of Ceramic Candle Filters towards Purification of Drinking Water

Performance Assessment of Household Water Treatment and Safe Storage in Kathmandu Valley, Nepal

Although many households in the Kathmandu Valley rely on household water treatment and safe storage (HWTS) to obtain drinking water, the safety of treated water has not been evaluated in actual usage. Therefore, we assessed the performance and maintenance of five HWTS methods used in 101 households. The choice of HWTS methods by households was primarily influenced by the raw water source, that is, jarred water users opted for boiling and groundwater users selected reverse osmosis with ultraviolet irradiation (RO-UV). While boiling and electric dispensers (ED) did not remove inorganic contaminants (ammonia nitrogen, arsenic, and manganese), ceramic candle filters (CCF) and RO-UV reduced them moderately. The HWTS methods reduced E. coli and total coliforms (TC) by 95.8 and 84.1%, respectively, but 11.8 and 69.3% of treated water samples remained positive for these two bacteria. Combined methods (CM) and RO-UV showed an inferior TC reduction compared to the simpler HWTS methods, boiling, CCF, and ED, possibly due to difficulties with regular maintenance and storage contamination. Therefore, it is recommended to choose simpler HWTS methods that meet the requirements of the household’s water sources rather than more expensive and difficult-to-maintain methods, which should be chosen only if the raw water contains high concentrations of inorganic contaminants.

Synergic Effects of Bed Materials and Catalytic Filter Candle for the Conversion of Tar during Biomass Steam Gasification

This work concerns the activities of the European project BLAZE that aims to integrate a pilot-scale gasifier unit with a Solid Oxide Fuel Cell (SOFC). The objective is to identify the optimal operating conditions for a gasifier and hot gas cleaning and conditioning unit to produce H2-rich syngas with contaminants levels within the limits for the safe operation of the SOFC (750 mg/Nm3 and 75 mg/Nm3 for toluene and naphthalene, respectively). Experimental tests were carried out on a bench-scale gasification plant with a catalytic filter candle placed in the freeboard, to study the influence of temperature (1032 up to 1137 K), bed materials (olivine or olivine/dolomite 80/20%), and a nickel-based catalyst. The tests with a ceramic filter candle filled with catalyst and the mixture of olivine and dolomite in the bed gave the best results in terms of gas composition and gas yield, but the tar content was still higher than the limits for the SOFC. To increase the residence time of the gas in the catalytic bed a new metallic filter candle was tested. This candle, with almost the same external volume, allowed doubling the amount of catalyst used. Under these conditions, the content of toluene and naphthalene was reduced below 150 and 50 mg/Nm3, respectively.

Mini-Review on Hot Gas Filtration in Biomass Gasification: Focusing on Ceramic Filter Candles

Biomass gasification is increasingly attracting interest in the research of biorenewable energy all over the world, as a carbon-neutral supplement to the conventional fossil energy. It can convert biomass to the burnable producer gas for heat and power production or synthesis of fuels and chemicals. However, its commercial applications are seriously interfered by the minor but unavoidable contaminants or impurities in the raw product gas, which cause severe problems in the downstream equipment. This paper reviews the recent progress on the hot gas filtration technologies for removing particulate matters (PMs) and tars from the biomass-derived product gas, focusing on ceramic filter candles, which are widely applied in the biomass gasification systems. Developments of PM characterization, hot gas catalytic filtration, and oxidative filtration as well as the numerical simulation of computational fluid dynamics in hot gas filtration are summarized in detail. It also critically discusses the major challenges and future opportunities in hot gas filtration and concludes that the combined oxidative filtration and catalytic filtration with highly efficient catalyst at moderate temperatures (<600 °C) should be the most economical option for the widespread commercial small-scale biomass gasification systems.

Development of catalytic ceramic filter candles for tar conversion

A catalyst with a high activity in tar conversion, impregnated on the ceramic hot gas filter material was developed. The aim of the experiments was to estimate the light-off temperature of the catalytic filter elements for naphthalene (tar model compounds) conversion and the long-term catalytic stability at a temperature of 700 °C. Configuration of the catalyst was optimized through improvements in coking resistance and long-term stability. The composition and morphology parameters of the filter material were considered. Both the impregnation methods and the composition of the impregnation solution were investigated and validated. The catalyst composed of Ni, Fe, Cr oxides, promoted with Pt (AlSi-Cat43-Pt), and impregnated on the ceramic-fiber filter composed of Al2O3(44%)/SiO2(56%) was found to be the most active catalyst. The designated catalyst was catalytically active at temperatures of about 700 °C, with a naphthalene conversion of around 93% over 95 h without catalyst deactivation. We found that the steam and gas compositions had an influence on the catalytic activity of the filter elements. The same catalytic filter was catalytically active for 115 h at a low concentration of H2O (10 vol%) and H2 (3 vol%) with a naphthalene conversion of 98% at 790 °C without significant deactivation.

Permeability and dust filtration behaviour of porous SiC ceramic candle filter

Porous SiC candle filter (∼660 mm L and 75 mm OD) were fabricated by ramming process using commercially available SiC powder (d 50 = 212 μm), with and without alumina and small amount (3 wt%) of clay as the major binder phase additives, following heat treatment at 1400 °C in air. Depending on the composition, porosity of the candle filters varied from 36 to 39 vol% and C-ring strength varied from 15 to 23 MPa. The air permeability and dust filtration efficiency of the candle filter were evaluated using laboratory made test set up. At room temperature, Darcian (k 1 ) and non-Darcian (k 2 ) permeability parameters varied from 1.9 to 2.2 × 10 −12 m 2 and 5.4–9.72 × 10 −8 m, respectively. Airborne fly ash particle filtration tests showed good performance of SiC candle filter with filtration efficiency of >97%.

Purifications of petroleum products contaminated water using modified rice husk ash filters

This study evaluated the effects of different ceramic candle filters made from blends of rice husk ash (RHA), polyethylene glycol (PEG), and clay for effectiveness in purifying petroleum products contaminated water. The filters were characterized for porosity, swellability and water permeability. Performances of the candle filters were evaluated based on the physicochemical analysis of the untreated and purified water samples. The parameters measured include total dissolved solids (TDS), hardness, phosphates, nitrates, and chloride. Results from this investigation indicated that water diffusion in the filters, depends on filter dimensions-as permeability increased with decrease in filter’s surface area. This was also seen in the average flux obtained for the candles. The filter EL4 has a flux of 0.0070 ml/min.cm2, EL3 has 0.0199 ml/min.cm2. Also, the porosity of the filters increased with the amount of porogen used. An improvement in physical appearance of the water samples was seen after purification of the contaminated water. The chloride and TDS content of the untreated water samples were 260.1 ± 7.705 mg/L and 596.7 ± 30.32 mg/L respectively, while the chloride and TDS contents of filtrates obtained from filter made from RHA/Eleme clay and PEG as porogen (EL3) to 246.4 ± 1.915 mg/L and 511.7 ± 13.3 mg/L respectively. All the filters increased the phosphate and nitrate contents of filtrates compared to the untreated water samples. Total polycyclic hydrocarbon was reduced up to 85% by EL4 filter. The values of heavy metals found in the water samples were within the permissible limit for irrigation water. The low preparation cost, ease of preparation and purification results of these candle filters will boost their applications for water remediation in areas with high level of contamination particularly for irrigation and other household purposes but not drinking and cooking.

Developing Zeolite Ceramic Filters For Purifying Open Water Sources In Rural Communities

Access to safe drinking water has been a challenge for most rural dwellers in Sub-Sahara Africa who rely on open water sources for their consumption and domestic activities. In attempt to purify water from these open water sources, this study looked at producing zeolite from kaolin with NaOH concentrations through crystallization process, develop ceramic candle filters and subsequent zeolite filter unit to purify unsafe water. Two procedures were used for the synthesis; pre-treatment or thermal activation of the kaolin at 6500C to get a dehydroxylated product called metakaolin and hydrothermal reaction of metakaolin in alkaline solutions for crystallization of the zeolite. The effect of the zeolite ceramic filter on the users was enormous. Results showed that properties such as turbidity removal, flow rate and coliform removal were within WHO standard after the purification. A pilot study of the zeolite ceramic filter showed improved health standards such as fewer diarrhea, nausea, cramps, vomiting and good skin growth.

Syngas conditioning by ceramic filter candles filled with catalyst pellets and placed inside the freeboard of a fluidized bed steam gasifier

Gasification is a very advantageous conversion process to obtain a fuel gas from organic wastes, however it also generates by-products, such as particulate and tar. These should be removed from the syngas for its smooth utilization in power generation devices and/or biofuels production. In this work, biomass gasification tests were carried out in a bench-scale fluidized bed gasifier with a ceramic filter candle filled with commercial Ni-catalyst pellets integrated in its freeboard, for the abatement of particulate and tar. The activity of catalyst was studied at different operating conditions (temperature and catalyst bed layout) and the results were analysed in terms of residual tar content and composition of the product gas. The catalyst resulted very effective, particularly in tests at higher temperature and with the partially filled candle configuration. Tars were reduced to 250 mg/Nm3 in the best case. The Ni-catalyst did not show deactivation during tests lasting 4 h.

Development and Tests of a Combined Filter for NOx, Particulates, and SO2 Reduction

AbstractThe idea of this innovative filter concept is to combine three individual flue gas technology treatment systems into one product to be more economic and efficient. The central part of the filter is a ceramic filter candle, which is used for common dust separation. The ceramic filter material is activated with modified catalysts to enable selective catalytic reduction at low temperatures (150–200 °C). To reduce acid components while simultaneously increasing dust separation, the activated filter candle surface is precoated with an absorbent. The developed filter is suitable for many applications, especially decentralized applications such as solid biomass combustion or utilization of biofuels in combined heat and power engines, which are target markets. The production of the filter material and the practical test using exhaust gas from a dual fuel engine operating with biofuels are described.

Development of De-NOx selective catalytic reduction catalyst using V2O5 –TiO2 supported on a ceramic filter candle

ABSTRACT This study reports the development of a V2O5-TiO2-based selective catalytic reduction (SCR) catalyst supported on alumina-silicate water filter candles for NOx abatement. The synthesised catalysts have been characterised by thermogravimetry/differential scanning calorimetry, X-ray diffraction, scanning electron microscope and measurement of NOx removal performance. The catalyst synthesised under optimal conditions shows NOx reduction efficiency of >97%. SCR performance has been augmented using O2 as a carrier gas. This simple, reproducible procedure can have wide applications in NOx abatement.

Assessing the Influence of Water Management and Rainfall Seasonality on Water Quality and Intestinal Parasitism in Rural Northeastern Brazil.

Introduction The drought in the Brazilian semiarid region has affected the quality of water. This study assessed the relationships between enteric parasitoses, water management, and water quality, correlating them with pluviometric seasonality. Methods Cross-sectional surveys were carried out in four rural communities at the beginning of the dry season (n=151), at the end of the dry season (n=184), and in the rainy season (n=199), in order to collect sociodemographic data, human fecal samples, and samples of the water used for human consumption for physicochemical and microbiological analyses. In 2015, water filters were provided to 30 households under study. Results There was an increasing trend in detection rates of commensal protozoa and the Entamoeba histolytica/Entamoeba dispar complex at the beginning of the rainy season, with detection rates of 6% in 2014 and 21.6% in 2016. Giardia intestinalis and Ascaris lumbricoides presented distinct temporal distributions, which peaked in 2015: 20.1% and 30%, respectively. The proportion of inhabitants drinking inadequate water was 55% at the beginning of the dry season and 28.8% at the end of the dry season, reaching 70.9% at the beginning of the rainy season. The presence of filters reduced this proportion among those who received the hollow ceramic candle filter. Conclusions Data suggest that the strategies to increase water supply in the Brazilian semiarid region can be ameliorated in order to improve the quality of drinking water.

Effects of temperature, dust concentration, and filtration superficial velocity on the loading behavior and dust cakes of ceramic candle filters during hot gas filtration

Abstract Ceramic candle filters (CFs) are commonly used in power generation processes because of their ability for durable operation at high temperatures. Two ceramic CFs were experimentally and theoretically evaluated in this study, one composed of mullite (30–20) and the other composed of alumina and silicon carbide (F-40), representing filters with high and low collection efficiency for conventional and advanced power generation. The effects of three critical parameters in CF operation (temperature, dust concentration, and filtration superficial velocity) on two performance measures (filter loading behavior and dust cake) were carefully investigated. The revised Endo’s expression was used to evaluate the resistance ( α c ) and porosity ( e ) of dust cakes that formed on a cylindrical CF. An analysis of pressure drops for both CFs and dust cakes revealed that the pressure drops increased with the operation temperature, which was solely due to the increase in air viscosity. However, the resistance and porosity of the dust cakes were still affected by the filtration temperature, even when the influence of temperature on the gas viscosity and volumetric flow rate was considered. Between 473 and 573 K, the overall steady-state α c and e of the dust cakes changed markedly for both CFs. Moreover, for the low-efficiency CF (F-40), improvement in the collection efficiency with the temperature depends on improved diffusional effects and may influence the corresponding dust cake structures.

Separation of carbon dioxide and nitrogen gases using novel composite membranes

Global warming is the major environmental issue caused by greenhouse gases, especially CO2. This demands urgent action to reduce or offset CO2 emission from power plants, which could be done using facilitated transport membranes (FTMs). In this context, CO2 selective carriers were prepared by blending polyvinyl alcohol (PVA) with three amines: ethylenediamine (EDA), diethylenetriamine (DETA), and triethylenetetramine (TETA). Then, the composite membranes were prepared using PVA–amine blend as the separation layer and ceramic candle filters as the support layer. The fabricated membrane was characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Furthermore, the effect of amine species, effect of TETA concentration, cross-linking agent content, pressure difference, and the thickness of the membrane on the permeance and selectivity of CO2 over N2 were investigated. The permeance and selectivity of CO2 through the membranes were in the following order: TETA &gt; DETA &gt; EDA. This order is related to the number of nitrogen atoms per amine molecule, which can be correlated to loading capacity and, consequently, to amine reactivity with CO2. Under optimized conditions, for a pure gas experiment, the maximum permeance of 6.9 GPU for CO2 gas and selectivity of 50 over N2 was obtained, whereas in the CO2/N2 gas mixture, the maximum permeance of 8.6 GPU and selectivity of 98 was obtained. The membrane was found to be stable for 264 h.

Do low-cost ceramic water filters improve water security in rural South Africa?

Abstract. This study examined the performance of a low-cost ceramic candle filter system (CCFS) for point of use (POU) drinking water treatment in the village of Hobeni, Eastern Cape Province, South Africa. CCFSs were distributed in Hobeni and a survey was carried out among their users. The performance of 51 CCFSs was evaluated by dip slides and related to human factors. Already after two-thirds of their specified lifetime, none of the distributed CCFSs produced water without distinct contamination, and more than one-third even deteriorated in hygienic water quality. Besides the water source (springs were preferable compared to river or rain water), a high water throughput was the dominant reason for poor CCFS performance. A stepwise laboratory test documented the negative effects of repeated loading and ambient field temperatures. These findings suggest that not every CCFS type per se guarantees improved drinking water security and that the efficiency of low-cost systems should continuously be monitored. For this purpose, dip slides were found to be a cost-efficient alternative to standard laboratory tests. They consistently underestimated microbial counts but can be used by laypersons and hence by the users themselves to assess critical contamination of their filter systems.

Gas conditioning in H2 rich syngas production by biomass steam gasification: Experimental comparison between three innovative ceramic filter candles

The biomass steam gasification is a promising path to obtain hydrogen-rich syngas and to improve the global efficiency for cogeneration purposes.The present study reports the results of a campaign of steam gasification tests performed in a bench-scale gasifier (0.1 m ID) housing in its freeboard a ceramic filter, in a temperature range of 800 °C–815 °C. Three new ceramic filters have been tested: (i) noncatalytic candle with new support, (ii) filter candle with catalytic layer, (iii) filter candle with new integrated catalytic foam system and results were compared to those obtained in tests without candle. The volume composition of the syngas was monitored and analyzed by online measurement by means of infrared – thermal conductivity detector (IR-TCD) facilities to evaluate the CO, CO2, CH4, H2, NH3 composition. The Topping Atmosphere Residue (tar) content was evaluated by gas-chromatograph mass spectrometer (GCMS) facility; gas yield, water conversion and char conversion were also calculated from direct measurements.The best results were obtained in the case of innovative catalytic filter in association with cycled olivine bed, obtaining gas yield equal to 1.80 Nm3/kgdaf (vs 1.00 Nm3/kgdaf without candle); observed to theoretical water conversion ratio equal to 0.88 (vs 0.33); H2 volume content equal to 56% (vs 39%); total tar content equal to 0.14 g/Nm3 (vs 6 g/Nm3).

Designing and testing of a portable filter for groundwater defluoridation and desalination, equipped with non-woven geotextiles

Using non-woven polypropylene geotextile, a filtration unit was designed for portable prototype filter capable of defluoridation and desalination. The filtration unit contains geotextile bag filled with mica and graphite sand. Emphasis was given to make the filter design as simple as possible that is suitable for rural areas. The designed filter was continuously tested for three months along with ceramic (Candle) filter and Pureit filter for comparative studies. The performance of the filters was evaluated on the basis of the percentage of residue removed by the individual filters and cleaning period of the filters. The results of the improvement in the water quality made by prototypes filter without cleaning show reduction in concentration of fluoride and electrical conductivity (EC) by 83.06 and 45.75%, respectively. While the other two filters despite weekly cleaning shows reduction in concentration of fluoride and EC by 74.20 and 30.04%, (ceramic filter) and 93.68 and 86.37% (Pureit filter), respectively. The prototype filter with very simple in design has performed better than other filters with complex designs. The test shows that uses of non-woven geotextiles (polypropylene) along with sand can provide an alternate solution to the expensive defluoridation and desalination processes.

Assessment of a membrane drinking water filter in an emergency setting.

The performance and acceptability of the Nerox(TM) membrane drinking water filter were evaluated among an internally displaced population in Pakistan. The membrane filter and a control ceramic candle filter were distributed to over 3,000 households. Following a 6-month period, 230 households were visited and filter performance and use were assessed. Only 6% of the visited households still had a functioning filter, and the removal performance ranged from 80 to 93%. High turbidity in source water (irrigation canals), together with high temperatures and large family size were likely to have contributed to poor performance and uptake of the filters.

Comparing the effectiveness of five low-cost home water treatment devices for Cryptosporidium, Giardia and somatic coliphages removal from water sources

This study compared the effectiveness and sustainability of five selected cost-effective home water treatment systems in removing Cryptosporidium and Giardia spp. from water sources. These systems included: silver impregnated porous pot (SIPP), biosand filter combined with zeolite (BSF-Z), biosand filter without zeolite (BSF-S), bucket filter (BF) and ceramic candle filter (CCF). The USEPA Methods 1623 were used for the isolation and the detection of the protozoan parasites. The flow rates of the devices ranged between 0.05 and 160.5 L/h. The average turbidity of the environmental intake water samples ranged between 1.47 and 42.93 NTU before filtration and between 0.05 and 14.49 NTU after filtration. The performance of the SIPP in removing the parasites (98–100% of both oocysts and cysts from synthetic water; 96–99.6% oocysts and 96.6–99.8% cysts from the environmental water sources) and in removing viral indicator (97.7–100%) was found to be significantly higher (p < 0.05) compared to other filters. In spite of its low flow rate, the SIPP filter consistently produced drinking water that complied with the limits set by the South African National Standards 241 in terms of turbidity and somatic coliphages.

Bactericidal activity and silver release of porous ceramic candle filter prepared by sintering silica with silver nanoparticles/zeolite for water disinfection

Porous ceramic candle filters (PCCF) were prepared by sintering silica from rice husk with silver nanoparticles (AgNPs)/zeolite A at about 1050 °C to create bactericidal PCCF/AgNPs for water disinfection. The silver content in PCCF/AgNPs was of 300–350 mg kg−1 determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and the average pore size of PCCF/AgNPs was of 50–70 Å measured by Brunauer–Emmett–Teller (BET) method. The bactericidal activity and silver release of PCCF/AgNPs have been investigated by flow test with water flow rate of 5 L h−1 and initial inoculation of E. coli in inlet water of 106 CFU/100 mL. The volume of filtrated water was collected up to 500 L. Results showed that the contamination of E. coli in filtrated water was <1 CFU/100 mL and the content of silver released from PCCF/AgNPs into filtrated water was <1 μg L−1, it is low, far under the WHO guideline of 100 μg L−1 at maximum for drinking water. Based on the content of silver in PCCF/AgNPs and in filtrated water, it was estimated that one PCCF/AgNPs could be used to filtrate of ∼100 m3 water. Thus, as-prepared PCCF/AgNPs releases low content of silver into water and shows effectively bactericidal activity that is promising to apply as point-of-use water treatment technology for drinking water disinfection.