Oct. 07, 2024
The research was carried out in the Kambata Tambaro zone, focusing on Hadaro and Tunto Woredas in three selected kebeles: Ajora, Tunto, and Lalo. The Kambata Tambaro zone is located approximately 247 km southwest of Addis Ababa, the capital of Ethiopia. This zone is situated between 500 and 3000 meters above sea level and features steep slopes at the base of the Anbericho, Dato, and Ketta Mountains. The zone borders Wolaita to the south, Dawro to the southwest, Hadiya to the northwest, Gurage to the north, and Halaba special woredas to the east.
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Clay soil samples were collected from Ajora, Tunto, and Lalo sites. Once collected, the clay was packed, labeled, and transported to a drying area. The clay was combined in equal proportions and sun-dried for a duration of seven days under the supervision of local artisans. The dried clay was then ground using a wooden mortar and pestle and screened through a 0.5 mm sieve. Sawdust was obtained from local furniture makers, similarly dried for seven days, ground, and screened with a 0.5 mm sieve. Grog was also ground with mortar and pestle, and passed through a 0.5 mm sieve.
The combined sawdust and grog were mixed dry for 40 minutes in varying proportions. Subsequently, water was added uniformly to the mixture of clay, sawdust, and grog, and mixed by wedging and rolling for another 40 minutes until a smooth, homogeneous blend was achieved. This mixture was then molded into blocks as shown in Table 1. The ceramic filters were designed in the shape of flower pots, discs, and candles.
Table 1: Percentage Composition of Clay, Sawdust, and GrogFull size table
The clay mixtures were shaped into flower pot forms using a plastic cup. These pots had walls thicker than 1 cm. The pressed materials were air-dried for three days and then dried in a designated area for about ten days to remove moisture that could cause cracking during firing. Firing transforms the ceramic materials into dense components by applying thermal energy. The sun-dried pots were fired in a furnace at various temperatures. Different batches of dry pressed ceramic filters were placed in a muffle furnace where they underwent sintering for 5 hours at temperatures of 700°C, 750°C, and 800°C, with a heating and cooling rate of 10°C for 5 hours. Filters coded 1, 4, and 7 were fired at 700°C, filters 2, 5, and 8 at 750°C, and filters 3, 6, and 9 at 800°C (Table 1).
Contaminated river water samples were taken from Hadaro Sana River following standard sampling procedures. Grab samples were collected with sanitized sterile plastic containers, transferred to large containers, and transported to the laboratory for analysis.
The flow rate was evaluated using water sourced from Sana River. The source water was continuously filled into the filters on the day of testing, and other water quality parameters were measured concurrently. The filter elements were soaked in pure distilled water for at least 8 hours prior to the flow rate testing to ensure consistent results. The amount of water percolated after one hour was measured. The water that passed through the filter flower pots was collected in a polyethylene cup where the time taken and the volume of discharged water were recorded (Martins). Average flow rates were observed throughout the production process, and the filter elements were cleaned immediately after testing.
The water from Sana River was known to contain indicator microorganisms, which were diluted with sterilized water at a ratio of 1:1000 by mixing 1 mL of river water with 999 mL of sterile water. Common indicator microorganisms used in this study included E. coli and total coliform. A membrane filtration technique was employed to detect and quantify total coliform and E. coli from both source and filtered water samples. The membrane used in the filtration process has pores approximately 0.45 µm in diameter, capturing larger microorganisms while allowing pure water to pass through. The filtration effectiveness was measured by the removal efficiency of the microbiological indicators.
A filter paper with a 0.45 µm pore size was placed onto the filter support base with sterile tweezers. The setup was shaken gently while pouring 100 mL of diluted river water for filtration. The funnel was rinsed with about 30 mL of distilled water twice. The membrane was carefully removed and transferred into Membrane Lauryl Sulphate Broth media on a metal Petri dish, which was then inverted and incubated at 32°C and 40°C for 16 hours to encourage the growth of total coliform and E. coli.
The counting of coliform forming units (CFU) was conducted using a magnifying device, and results were expressed in CFU/100 mL. Microbial removal efficiency was calculated using the following formula:
$${\text{\% Removal efficiency }} = \frac{C\, before - C \,after}{C\, before } \times 100$$
(1)
Where C is the influent microbial concentration in the raw water sample (cfu/100 mL) and the effluent concentration is the microbial concentration in filtered water samples (cfu/100 mL).
Turbidity levels in the influent and effluent water samples were measured using a portable turbidity meter (CL52 D NEPHELOMETER). The turbidity removal efficiency of ceramic filters was evaluated through the same river water samples. A sample of 15 mL was analyzed, comparing its turbidity to that of the distilled water with a baseline turbidity of 2 NTU. The turbidity of source water was measured prior to filtration, followed by testing the turbidity of the effluent after it passed through the different filters.
The turbidity reduction was calculated using the formula:
$${\text{Turbidity}}\left( {\text{\% }} \right) = \frac{Turbidity\, of\, source\, water - Turbidity\, of\, filtered\, water}{Turbidity\, of\, source\, water } \times 100\%$$
(2)
The efficiency of ceramic filter elements in removing water hardness was evaluated using the complexation titration method with EDTA and Eriochrome Black T (EBT) as an indicator. The concentrations of calcium and magnesium cations responsible for water hardness were determined using a prepared laboratory solution using 0.1 M magnesium solution and a calcium chloride solution. Titration was performed at a pH of 10 within an NH3/NH4+ buffer, ensuring accurate complexation with IIA group ions while avoiding interference from other cations that may be present.
For each trial, 20 mL of filtered water was pipetted into a clean conical flask with 2 mL of buffer solution and 1 mL of EBT, before titrating with EDTA solution. Concentrations of metal ions were obtained reflecting their presence in parts per million (ppm), allowing for the evaluation of removal efficiencies across various filter codes. The chemical reactions occurring at the endpoint are:
$${\text{H}}_{ 2} {\text{Y}}^{ 2- } \left( {\text{aq}} \right) \, + {\text{ MgIn}}^{ - } \left( {\text{aq}} \right) \, \to {\text{MgY}}^{ 2- } \left( {\text{aq}} \right) \, + {\text{ HIn}}^{ 2- } \left( {\text{aq}} \right)$$
(3)
The effectiveness of ceramic filters in removing iron was tested using a single beam UV-visible spectrophotometer (XP-P, China) with water samples sourced from the Sana river. Mohr's salt was dissolved to create a stock solution for calibration of the spectrophotometer, leading to standard solutions of different concentrations being prepared. The absorbance of the resulting orange-red complex was measured at 510 nm, after appropriate preparations including the addition of HCl, hydroxylamine, sodium acetate, and phenanthroline to create stable analytic conditions.
Filtered and unfiltered water samples underwent the same procedure to measure the absorbance, leading to the derivation of their respective iron concentrations in ppm based on a calibration curve.
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Highlighted Content:The nitrite levels were analyzed in the Analytical Chemistry laboratory at Hawassa University utilizing a UV-visible spectrophotometer. The prepared solution of 0.01 M NaNO2 was percolated through the ceramic filters to evaluate their effectiveness in nitrite removal. A violet complex was formed through diazotization with paranitroaniline under acidic conditions, followed by interactions with 1-naphthol under basic conditions to provide a colorful metric for analysis.
Conductivity and pH of both source and filtered water were analyzed using a Conductivity Meter and a pH-016 pH METER, respectively. Standard solutions of KCl ensured instrument calibration for accurate conductivity measurements, while buffer solutions at pH 4 and 8 were utilized to stabilize pH evaluations for both water types.
The porosity of ceramic filters was evaluated using a direct water absorption method. This destructive method involved measuring the weight of samples before and after water saturation to calculate average porosity across multiple specimens, ensuring a thorough understanding of the filtration capabilities offered by the ceramic materials. The apparent porosity (P) was calculated using the following equation:
$$P = 100\left[ {\frac{Wsaturate - Wdry}{Wsaturate - Wunderwater}} \right]$$
(4)
Data analysis was conducted using the Statistical Analysis System (SAS Institute). The efficiency of the ceramic filters fabricated from varying proportions of sawdust, grog, and clay was subjected to analysis of variance (ANOVA) using the general linear model procedure. The Least Significant Difference (LSD) test was utilized to discern efficiency variances at a significance level of P = 0.05.
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