Comparison of coagulation performance and floc properties using a novel zirconium coagulant against traditional ferric and alum coagulants

Abstract

Coagulation in drinking water treatment has relied upon iron (Fe) and aluminium (Al) salts throughout the last century to provide the bulk removal of contaminants from source waters containing natural organic matter (NOM). However, there is now a need for improved treatment of these waters as their quality deteriorates and water quality standards become more difficult to achieve. Alternative coagulant chemicals offer a simple and inexpensive way of doing this. In this work a novel zirconium (Zr) coagulant was compared against traditional Fe and Al coagulants. The Zr coagulant was able to provide between 46 and 150% lower dissolved organic carbon (DOC) residual in comparison to the best traditional coagulant (Fe). In addition floc properties were significantly improved with larger and stronger flocs forming when the Zr coagulant was used with the median floc sizes being 930 μm for Zr; 710 μm for Fe and 450 μm for Al. In pilot scale experiments, a similar improved NOM and particle removal was observed. The results show that when optimised for combined DOC removal and low residual turbidity, the Zr coagulant out-performed the other coagulants tested at both bench and pilot scale.

Optimization of coagulation-flocculation process for colour removal from Azo dye using natural polymers: response surface methodological approach

“…Lastly, biological treatment techniques used are aerobic degradation, anaerobic degradation, and living/dead microbial biomass [6]. Coagulation-flocculation is an already established process for contaminant removal from most wastewaters ranging from wastewater containing: biochemical oxygen demand; BOD [7], colour [8], dissolved organic carbon; DOC [9], turbidity [10], chemical oxygen demand; COD [11], grease and oil [12], total suspended solids; TSS [7], heavy metals [13][14]. Coagulation-flocculation is an efficient unit process used for colour removal from industrial wastewater due to its efficiency and simplicity to operate [12].…”

Removal of model viruses, E. coli and Cryptosporidium oocysts from surface water by zirconium and chitosan coagulants

“…Zirconium effectiveness is usually explained in terms of its valency (Jarvis et al, 2012;Hussain et al, 2014), which presumably provides higher charge neutralization power, which is necessary for destabilization of microbial and other colloids. This also explains the higher Zr affinity to organic matter shown in the present and previous studies (Jarvis et al, 2012).…”

“…Optimal coagulation conditions were defined, based on residual particles (turbidity) and natural organic matters (NOM, colour) in the filtrate samples. Each coagulant was screened under stable pH conditions, which corresponded to the lower limit of the optimal pH ranges, reported in the literature: 5.7-5.8 for PACl and 4.0-4.2 for Zr and chitosan (Christensen et al, 2016;Jarvis et al, 2012;Ødegaard et al, 2010). A range of low doses was further tested in pilot scale to detect the minimal effective doses that provided turbidity <0.…”

Investigation of the Effects of Salinity and Temperature on the Removal of Iron from Water by Aeration, Filtration, and Coagulation

“…Under the increasing weight of flocs, they become heavy enough to sink to the bottom during sedimentation. Coagulation by hydrolizing metal salts, typically of iron (Fe) or aluminium (Al), is the main reaction stage that drives the removal of natural organic matter and other contaminants in water treatment [4]. In the course of this investigation we have determined efficiency of iron removed with the use of alum coagulant against the aeration process.…”

“…Salts that have been used for this purpose were sodium chloride NaCl, sodium sulfate Na 2 SO 4 , and iron sulfate VI FeSO 4 . Preparation of model water consisted of mixing with the use of a magnetic stirrer and 4-liter portions of distilled water with salt doses presented in Table 1 while maintaining equal content of ferrous sulphate FeSO 4 VI.…”