Removal of Iron and Organic Substances From Groundwater in an Alkaline Medium

Abstract

The article discusses the effectiveness of alkalinisation with calcium hydroxide or sodium hydroxide in the treatment of groundwater from Quaternary formations with an increased content of total iron (up to 6.82 mgFe/dm3) and organic substances (TOC up to 5.60 mgC/dm3). The aim of the research was to determine the effectiveness of the groundwater treatment, in particular, the removal of iron and organic substances in the sorption process and co-precipitation with calcium carbonate and magnesium hydroxide. The correction of the reaction was carried out with aqueous solutions of calcium hydroxide and sodium hydroxide in the pH range from 8.5 to 10.5. As the pH of the water increased, the efficiency of its treatment increased. The treatment results depended on the type of alkalizing reagent, especially in the case of removal of organic substances, reduction of colour and organic substances fixed in iron-organic complexes. Higher suitability of calcium hydroxide than sodium hydroxide in alkalinisation has been demonstrated. Calcium ions introduced into the treated water together with calcium hydroxide probably neutralized organic anions fixed in iron-organic complexes and determining colour and TOC, increasing their susceptibility to adsorption.

The Influence of the Presence of Iron in Highly Alkaline Polyaluminium Chlorides on the Effectiveness of Precursors of Disinfection by-Products Removal

“…These interactions lead to complex formations and to potential solid precipitation. It was moreover confirmed that the constant durability of the iron-organic complex increases along with an increase in pH, which is most likely caused by a growing dissociation of functional -COOH and -OH groups [11,[31][32][33]. The reason behind the formation of chromatic iron-organic complexes over the course of coagulation with the highly-alkaline PAXXL1911 coagulant may have been the high pH, falling into the range of 7.86 to 8.00 ± 0.10, in which the functional groups of -COOH and -OH organic substances are more reactive in relation to iron ions and have been also the introduction of additional iron ions along with the coagulant, which may have reacted with the organic substance present in the treated water.…”

“…The coloured iron-organic complexes formed during PAXXL1911 coagulation most likely exhibited the character of protective colloids, hence leading to the significantly higher turbidity that followed PAXXL1911 coagulation as compared to the turbidity after PAXXL10 and PAXHP908 coagulation which were respectively: from 2.20 to 3.30 ± 0.1 NTU (PAXXL1911), from 1.10 to 2.10 NTU (PAXXL10) and from 1.00 to 1.40 ± 0.1 NTU (PAXHP908). According to numerous researchers [11,[31][32][33]44], the reasons for the stabilisation of iron by organic substances is the formation of chelate complexes and the formation of so-called protective colloids of a hydrophilic nature. According Kwakye-Awuah et.al [45] the iron ion pollution in groundwater may interact with the dissolved constituents, such as dissolved organic carbon (DOC), present as a humiclike material.…”

“…The results of the research presented by the author in previous publications [9,31] showed that iron coagulants provide less efficiency in removing iron and organic substances from water than aluminum coagulants, due to the possibility of creating additional colloidal and dissolved iron-organic complex between organic substances present in the treated water and iron ions introduced with the coagulant. In the publications [32][33][34] it was also shown that the formation of iron-organic complex is favoured by the increase of the dissociation degree of organic substances as a result of the increase in pH to a value of approx. 8, at which also H + ions from hydroxyl groups (-OH) are dissociated.…”

Aeration Strategies for the Removal of Iron From Water Manufacturing Industry

“…pH air yang berpengaruh terhadap kesadahan kadar Fe dalam air, proses korosif dapat terjadi jika pH air yang rendah sehingga akan menyebabkan larutnya besi dan logam lainnya dalam air, pH yang rendah kurang dari 7 dapat melarutkan logam. Besi yang ada dalam air berbentuk ferri atau ferro dalam keadaan pH rendah, dimana bentuk ferri tidak larut dalam air dan akan mengendap serta tidak dapat dilihat dengan mata sehingga mengakibatkan air menjadi berbau, berwarna, dan memiliki rasa (Krupińska, 2019).…”

Removing Iron and Organic Substances from Water over the Course of Its Treatment with the Application of Average and Highly Alkaline Polyaluminium Chlorides

“…The aim of this work was to determine whether the presence of iron ions in highly basic polyaluminium chlorides and increasing the pH of the water during the coagulation process influences the final efficiency of purifying water obtained in the entire technological process due to the possibility of creating additional colloidal or dissolved iron-organic complexes between organic substances present in the water and iron ions introduced along with the coagulant. The use of high-base polyaluminium chlorides may facilitate the formation of iron-organic complexes due to increasing the water pH to ≥8 during the coagulation process, which could cause complete dissociation of organic substances and this creates good conditions for the formation of iron-organic complexes [ 4 , 5 , 6 , 7 , 8 , 16 , 29 , 30 ]. The research was conducted on a laboratory and technical scale.…”