Exploitation of Fenton and Fenton-like reagents as alternative conditioners for alum sludge conditioning

The use of Fenton＇s reagent （Fe^2＋/H2O2） and Fenton-like reagents containing transition metals of Cu（Ⅱ）, Zn（Ⅱ）, Co（Ⅱ）, and Mn（Ⅱ） for an alum sludge conditioning to improve its dewaterability was investigated. The results obtained were compared with those obtained from conditioning the same alum sludge using cationic and anionic polymers. Experimental results show that Fenton＇s reagent was the best among the Fenton and Fenton-like reagents for the alum sludge conditioning. A considerable effectiveness of capillary suction time （CST） reduction efficiency of 47% can be achieved under test conditions of Fe^2＋/H2O2 = 20/125 mg/g DS （dry solid） and pH 6.0. The observation of floc-like particles after Fenton＇s reagent conditioning of alum sludge suggested that the mechanism of Fenton＇s reagent conditioning was different from that of polymer conditioning. In spite of the lower efficiency in the CST reduction of Fenton＇s reagent in alum sludge conditioning compared to that of polymer conditioning, Fenton＇s reagent offers a more environmentally safe option. Tiffs study provided an example of proactive treatment engineering, which is aimed at seeking a safe alternative to the use of polymers in sludge conditioning towards achieving a more sustainable sludge management strategy.

Adsorptive Removal of Fluoride from Water by Heat-Treatment Waterworks Alum Sludge

Alum sludge （AS） is a world-wide by-product generated in the drinking water treatment process when aluminum salts are used as coagulant. Its high AI content makes it a potential adsorbent for flouride removal from water. A high performance adsorbent was fabricated via heat treatment of AS and batch adsorption experiments were carried out to investigate its flouride adosroption performance. The results indicated that AS treated at 300℃ （AS300） for 1 h had the highest adsorption capacity for fluoride （52.9% fluoride removal）. The adsorption of fluoride by AS300 fitted better the Langmuir isotherm model than the Freundlich model. The maximum fluoride adsorption capacity of AS300 increased from 4.0 to 9.3 mg/g sludge when reaction temperature increased from 15 to 35 ℃. Thermodynamic parameters showed that the adsorption of fluoride by AS was spontaneous and endothermie. Hence higher temperature was favorable for fluoride adsorption. The adsorption process followed the pseudo-second-order equation. In addition, the fluoride adsorption on AS300 decreased from 4.3 to 2.5 mg/g sludge when the solution initial pH increased from 4.0 to 9.0, which meant that adsorption capacity was greatly dependent upon the initial pH of the solution. The results provide new insight into the resource utilization of AS for fluoride removal.

Preparation of elastomeric nanocomposites using nanocellulose and recycled alum sludge for flexible dielectric materials

Flexible dielectric materials with environmental-friendly,low-cost and high-energy density characteristics are in increasing demand as the world steps into the new Industrial 4.0 era.In this work,an elastomeric nanocomposite was developed by incor­porating two components:cellulose nanofibrils(CNFs)and recycled alum sludge,as the reinforcement phase and to improve the dielectric properties,in a bio-elastomer matrix.CNF and alum sludge were produced by processing waste materials that would otherwise be disposed to landfills.A biodegradable elastomer polydimethylsiloxane was used as the matrix and the nanocompos­ites were processed by casting the materials in Petri dishes.Nanocellulose extraction and heat treatment of alum sludge were con­ducted and characterized using various techniques including scanning electron microscopy(SEM),thermogravimetric analysis/derivative thermogravimetric(TGA/DTG)and X-ray diffraction(XRD)analysis.When preparing the nanocomposite samples,various amount of alum sludge was added to examine their impact on the mechanical,thermal and electrical properties.Results have shown that it could be a sustainable practice of reusing such wastes in preparing flexible,lightweight and miniature dielectric materials that can be used for energy storage applications.

Evaluation of reusing alum sludge for the coagulation of industrial wastewater containing mixed anionic surfactants

A coagulation-flocculation process is typically employed to treat the industrial wastewater generated by the consumer products industry manufacturing detergents, soaps, and others. The expenditure of chemicals including coagulants and chemicals for pH adjustment is costly for treating this wastewater. The objective of this study was to evaluate the feasibility of reusing the aluminum sulfate （alum） sludge as a coagulant or as a coagulation aid so that the fresh alum dosage can be minimized or the removal efficiency can be enhanced. The experiments were conducted in a jar-test apparatus simulating the coagulation-flocculation process for simultaneous removals of organic matters, anionic surfactants, suspended solids, and turbidity. At the optimum initial pH value of 10 and the fresh alum concentration of 400 mg/L, the total suspended solids （TSS）, total chemical oxygen demand （TCOD）, total anionic surfactants, and turbidity removal efficiencies were 71.5%, 76.4%, 95.4%, and 98.2%, respectively. The addition of alum sludge as a coagulant alone without any fresh alum addition could significantly remove the turbidity, TCOD, and anionic surfactants. The TSS was left in the supernatants after the settling period, but would subsequently be removed by adding the fresh alum. The TSS, TCOD, and turbidity removal efficiencies were also enhanced when both the alum sludge and the fresh alum were employed. The TCOD removal efficiency over 80% has been accomplished, which has never fulfilled by using the fresh alum alone. It is concluded that the alum sludge could be reused for the treatment of industrial wastewater generated by the consumer products industry.

Optimisation of zeolite LTA synthesis from alum sludge and the influence of the sludge source

Generation of alum sludge(AS)at drinking water treatment plants represents an environmental liability and adds to the cost of water purification.Consequently,this study explored the feasibility of using low and high carbon containing alum sludge from two water treatment plants to synthesize zeolite LTA.The hypothesis was that zeolite LTA synthesis was dependant upon alum sludge source and that a range of strategies may be required to optimize zeolite crystallinity.Zeolite characteristics such as morphology,phase composition,crystallinity,and particle size distribution were recorded."One pot"hydrothermal synthesis of precursor gel with molar composition 4.2 Na2O:Al2O3:1.2 SiO_(2):168 H2O at 80℃ for 3 hr resulted in 25 and 46 wt.%zeolite LTA from high and low carbonaceous sludge,respectively.Prior to hydrothermal reaction stage it was discovered that ageing of the gel,addition of zeolite LTA seeds,ultrasonic treatment and calcination all promoted zeolite LTA formation.Calcination of the alum sludge at 700℃ for 2 hr before hydrothermal synthesis resulted in particle size reduction and the highest amount of crystalline zeolite LTA:79 wt.%from low carbon sludge and 65 wt.%from high carbon sludge.Notably,the zeolite crystallinity reported in this study was the higher than previous studies on this topic.The outlined approach may allow value adding of alum waste and produce a commodity which could be used locally by the water treatment plant as a water softener.

Valorisation of alum sludge to produce green and durable mortar

Alum sludge is a typical by-product of drinking water treatment processes.Most sludge is disposed of at landfill sites,and such a disposal method may cause significant environmental concern due to its vast amount.This paper assessed the feasibility of reusing sludge as a supplementary cementitious material,which could efficiently exhaust stockpiled sludge.Specifically,the pozzolanic reactivity of sludge at different temperatures,the reaction mechanism of the sludge-cement binder,and the resistance of sludge-derived mortar to microbially induced corrosion were investigated.The obtained results indicated that 800℃ was the optimal calcination temperature for sludge.Mortar containing sludge up to 30%by weight showed comparable physical properties at a curing age of 90 days.Mortar with 10%cement replaced by sludge can significantly improve the resistance to biogenic corrosion due to the formation of Al-bearing phases with high resistance to acidic media,e.g.,Ca_(4)Al_(2)O_(7)·xH_(2)O and strätlingite.