Comparison of lime and alum as oily sludge conditioners
ABSTRACT Chemical conditioning improves sludge dewatering. Choice of chemical conditioners is very much dependent on the characteristics of the sludges and the type of dewatering devices. Lime, alum, ferric chloride and polyelectrolytes are commonly used chemical conditioners. Anaerobic digested sludge samples collected from a sewage treatment plant with different oil contents varying from 1.8% to 8.0% by weight have been examined in the laboratory to find out their specific resistance, capillary suction time and filter yield. Lime and alum were used separately as conditioners. Different dosages of conditioner varying from 2% to 12% by weight were used to determine the optimum chemical dosage for varying oil contents. Lime dosages of about 6% were found to yield favourable characteristics. Addition of alum decreases the specific resistances and capillary suction times of oily sludges rapidly up to 4% dosages. Alum dosages beyond 4% only increase the solids content in the sludge cake and increase the sludge volume to be handled. A correlation between CST and specific resistance to filtration was established. CST can be measured easily and quickly in the laboratories. Using the CST and the correlation a quick prediction on dewaterability can be established.
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ABSTRACT: Fly Ash (FA) is obtained by electrostatic or mechanical precipitation of dust-like particlesfrom the flue gases of furnace fired with coal or lignite at 1100 to 1400Â°C. About 95-99% of Fly Ashconsists of oxides of Si, Al, Fe and Ca, about 0.5 to 3.5% consists of Na, P, K and S and the remainderis composed of trace elements. PFA has also been used as an adsorbing material when applied intreatment effluents. The use of Fly Ash as a chemical conditioner has previously been investigatedwith results indicating that Fly Ash does facilitate the filtering process since it decreases both specificresistance and capillary suction time. Therefore, the aim of this paper was to assess the potential ofPFA as an ameliorant for soil artificially spiked with various Lead compounds (PbSO4, PbCO3, PbNO3and PbS). Additions of quicklime and Fly Ash to the contaminated soils effectively reduced heavymetal leachability well below the regulatory limits for hazardous wastes. The results showed the effectof PFA on leaching of lead was significant for all the samples. A high interaction value depictingsampling effect over the use of the PFA as an ameliorant was observed. The order of the differencebetween samples treated with PFA and without PFA was PbNO3 > PbSO4 > PbCO3 > PbS (17 mg L 1 )when compared to that of the control. The results also demonstrated that, effect of filtration and PFAas an ameliorant had a significant effect in reducing toxicity. However, it is important to consider thesource of PFA, as certain sources could in essence impart certain toxic elements, defeating the primarypurpose of amelioration.American Journal of Environmental Sciences. 01/2005;
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ABSTRACT: Oily sludge produced from a petrochemical industry was used to investigate the improvement of its dewatering properties. The oil content (OC) and the dry solid content (DS) of the raw sludge were respectively, 15% and 3.6% by weight. The capillary suction time (CST) and the specific resistance to filtration (SRF) of the raw petrochemical industrial sludge were found to be 2000s and approximately 5.5x10(16)m/kg, respectively. Conventional chemical conditioners such as alum, lime, and polyelectrolyte, and less conventional ones like fly ash, gypsum, and bentonite were used in the sludge conditioning studies. Conventional chemical conditioners gave better results for the enhancement of the dewatering capacity of the sludge. The best result was obtained by using 0.9% cationic polyelectrolyte by weight, and a decrease of 99%-95% were achieved for CST and SRF, respectively, when this dosage of cationic polyelectrolyte was used.Journal of Hazardous Materials 07/2007; 144(1-2):323-7. · 4.17 Impact Factor