Aquatic humic substances, iron, and manganese removal by ultrafiltration and nanofiltration membranes combined with coagulation–flocculation–sedimentation

Abstract

A B S T R A C TIron and manganese removal is made conventionally by oxidation methods; however, when aquatic humic substances (HS) are present, they can affect the removal, with another treatment process being necessary. This study focused on performance of ultrafiltration (UF) and nanofiltration (NF), preceded by coagulation, flocculation, and sedimentation stages for iron, manganese, and HS removal, with two water sources that present superior levels of humic compounds, and measured by dissolved organic carbon (DOC) and UV absorbance at 254 nm. Coagulation, flocculation, and sedimentation combined with UF/NF efficiently removed dissolved iron, HS, apparent color, and turbidity. Almost total iron removal was already attained in the prior steps of coagulation, flocculation, and sedimentation, obtaining final values of dissolved iron of less than 0.001 mg L −1 for the two types of water studied. However, the complete system did not appear effective (less than 50% efficiency) in dissolved manganese removal, although a significant reduction in the HS was achieved (approximately 80% after UF and 90% after NF measured as DOC, for two types of water). Pretreatment was shown to be effective in reducing the loss of filtration flow because of the removal of high-molecular-weight HS, thus minimizing the formation of fouling on the membrane.

Adapting direct filtration to increasing source water dissolved organic carbon using clarification and granular activated carbon

“…Since these particles are already precipitated, they cannot be removed by the oxidation–precipitation mechanism, which is utilized by permanganate treatment (Carlson et al, 1997). Additionally, these colloids can be challenging to destabilize with alum, making them difficult to remove by coagulation (Chery Leal et al, 2015; Chiswell & Huang, 2006). The JDKWSP draws water from the epilimnion, which may explain the poor Mn removal performance during the summer and early fall (phases A and B).…”

“…Additionally, these colloids can be challenging to destabilize with alum, making them difficult to remove by coagulation (Chery Leal et al, 2015;Chiswell & Huang, 2006). The JDKWSP draws water from the epilimnion, which may explain the poor Mn removal performance during the summer and early fall (phases A and B).…”

“…Insufficient NOM removal can contribute to undesirable color, taste, and odor problems; impact the biological stability of distributed water (Hammes et al, 2010); and act as a carrier of trace metals (e.g., Pb) in distribution systems (Trueman et al, 2017). Pre‐oxidation processes (e.g., potassium permanganate, KMnO 4 ) for Fe and Mn may also become less efficient in the presence of elevated NOM (Anderson et al, 2023; Chery Leal et al, 2015; Knocke et al, 1987; Krupinska, 2017). Accordingly, many aspects of surface water treatment may be impacted by the phenomenon of increasing DOC.…”

Effects of High Concentrations of Organic and Inorganic Pollutants in Waste Water and Drinking Water on Nanofiltration Membrane Behavior

“…Investigations have shown that spring water containing low iron (0.09-0.26 mg/L) and manganese (0.05-0.1 mg/L) content in the presence of NOM (2-34 mg TOC/L) can be successfully treated with nanofiltration [44]. Oxidation, coagulation, flocculation, and sedimentation can be used as UF and NF pretreatments for water that contains iron and manganese [45]. NF is also proven as a promising technique for removal of large manganese quantities from mine waste water.…”