Characterization of alum sludge for reuse and disposal

The properties of spent drinking water treatment sludge (WTS) were investigated to determine its physical and chemical properties. WTS was obtained from the Semanggar Water Treatment Plant, Kota Tinggi, Johore, Malaysia. Bulk density, particle density, porosity, surface area, particle size, moisture content, ash content, chemical composition, leachability of heavy metals, pH and the total organic carbon (TOC) were determined. Surface and other physicochemical properties were also studied using the scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), X-ray diffractometer (XRD), TGA, FTIR, BET single point surface area analyzer, and TOC analyzer. Results showed that the particle size, bulk density and particle density of WTS were 2-5 μm, 0.831 ± 0.061 g/cm3 and 2.66 ± 0.029 g/cm3, respectively. The porosity was 68-69% with surface of 38.92 m2/g and ash content of 67%, reflecting the high TOC of 1440.37±14.71. The sludge contained 29% moisture and showed a pH value of 4.28 in solution. Analysis of acid digest indicated a high content of Al and Fe. The WTS were shown to leach very low levels of selected heavy metals

A simple voltammetric determination of metsulfuron-methyl in water samples using differential pulse cathodic stripping voltammetry

The voltammetric determination of metsulfuron-methyl, a type of pesticide, was investigated on a hanging mercury drop electrode using a differential pulse cathodic stripping voltammetry technique. The experimental parameters, such as the pH of the Britton-Robinson buffer, accumulation time, accumulation potential and initial potential were optimized for the metsulfuronmethyl determination. A well-defined reduction peak was observed at pH 2.0 to 4.0 in the potential range of -0.75 to -1.0 V. The pH of 2.0 was chosen as the optimum pH due to a good stripping signal of the reduction peak. There were no significant interfering ion effects on the electroanalysis of metsulfuron-methyl. The optimized parameters were then used to determine metsulfuron-methyl in the commercial pesticide Ally. The proposed method was highly sensitive due to the lower limit of determination (0.04 mg/L), being relatively selective, and consisting of good precision. The recovery values achieved were about 93% in water samples for this analysis

Studies on potential of Portland cement mortar for binding of waterworks sludge to reduce heavy metal leaching

The investigation of heavy metal leaching and physicochemical properties of cement-solidified waterworks sludge (CMWWS) formed by incorporating waterworks sludge (WWS) into cement mortar was carried out. The chemical composition, compressive strength and other physicochemical properties of the CMWWS cube specimens were determined using field emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD) and Fourier transform-infrared spectroscopy (FTIR). The major type of chemical components present in CMWWS was found to be Al and Fe. The increasing amount of WWS added to cement mortar resulted in the increasing of organic matter, urchin-like morphology and clear peak intensity. At the end of 28Â days of curing, the soaking solution became strongly basic and CMWWS cube specimens leached out higher amount of heavy metals. The compressive strength of CMWWS increased up to a WWS percentage of 10%, and basic (pHÂ >Â 7) curing solution was found to be better than water for curing purposes. It is concluded that solidification–stabilisation (S/S) technique is able to effectively reduce the leaching of heavy metals from the WWS and CMWWS containing up to 10% WWS can be used as construction material

Leachability study of metals from synthetic and natural alum sludge using different eluting medium

Effect of pH on metal coagulation with alum and the ability of the metals to leach out from synthetic and natural alum sludge was evaluated. The potential of pH on coagulation was studied using cadmium, chromium, copper, iron, manganese, nickel, lead and zinc with alum solution at pH 2, 4, 6, 7, 8, 10 and 12. Leachability of metals from synthetic alum sludge (SAS) and natural alum sludge (NAS) were investigated using the extraction test. The NAS was obtained from a water treatment plant in Malaysia. Leaching eluent consisted of distilled water, 0.1 M solution of hydrochloric acid, acetic acid, ammonium hydroxide and sodium hydroxide. The results showed that more than 90% of the metals were effectively removed using alum in the pH range of 8-12. All the metals were found to leached out easily from the SAS in all eluents used except for Mn and Ni which leached out in base eluents suggesting that the binding within in the prepared SAS is weak and easily dissolved in acidic medium. For NAS, the level of leached metal was found to be below 5 ppm, except for Fe due to their presence in alum and soil colloids during the coagulation process. The experimental results showed that metals found in NAS did not leach out easily, thus it can be considered safe for reusing purposes