Domestic water filter for treatment of arsenic contaminated water: Domestic water filter

Abstract

Water is precious and essential resource required for surveillance of all forms of life on earth. Maintaining the availability of safe and pure water is of great concern [1-2]. The quality of available water is being profusely contaminated by various heavy metals. One such heavy metal is arsenic. Contamination of arsenic in ground water, eventually in drinking water is a universal problem. The World Health Organization (WHO) had categorized arsenic as most toxic and carcinogenic to human being [3-4]. The presence of arsenic in water reservoir could cause various health hazardous, such as kidney, bladder, skin and lung cancers, diabetes, cognitive and neurological disorder in children [5-7]. Thus, there is an urgent need to evacuate arsenic ions from drinking water to safe-guard the humans and environmental ecosystem in the arsenic affected area. Different physio-chemical approaches like exchange of ions, flocculation, separation of membrane, exchange and oxidation are used presently for arsenic treatment [8-9]. Even though these methods are widely used, they have many drawbacks such as disposal problems and handling, high sludge generation, technical constraints, high cost, etc [10]. Recent research tries to discover effective method and alternative low-cost technique for evacuation of heavy metals. Biosorption has risen as the best option due its cost effectiveness,sustainability and simplicity [11-12].

This work aims at developing cost effective, sustainable and efficient filter for decontamination of arsenic from water. The biosorption ability of abundantly available plant material ‘Moringa oleifera seed’ for the expulsion of trivalent arsenite and pentavalent arsenate from waste water was investigated by performing packed column tests under various experimental conditions like bed depth, feed volumetric flow rate and initial arsenic concentration. A glass vertical column of 30 mm inner diameter and 100 mm height was used to carry out column studies. An inert base support of stainless sieve followed by 2 cm³ of glass wool was incorporated in column for even distribution of arsenic solutions, on top of which Moringa oleifera seed powder of desired height was packed. Glass beads of 1 cm height were put on top of packing to provide support. Continuous process was performed by pumping 100 µg/L concentration of arsenic solutions in an up-flow mode at a desired flow rate using a calibrating peristaltic pump at room temperature and at optimum pH (pH 7.5 for arsenic (III), pH 7 for arsenic (V)). The outlet was manually collected at the top of the column at regular interval of 20 minutes. The column studies were continued till fully saturation condition of the column was noticed. The residual arsenic solutions concentration was analysed using an atomic absorption spectrometer.

The findings from column operations revealed that value of maximum arsenic uptake was 88.6% and also values of maximum arsenic uptake, exhaustion and breakthrough time enhances with rise in bed depth, reduces with rise in feed volumetric flow rate and initial arsenic concentration. The continuous packed column data for arsenic were well fitted to the Thomas model with the regression coefficient ranges 0.969–0.986 [Table 1]. Moreover, the q_th values obtained from Thomas model are similar to the experimental breakthrough capacities q_exp. The FTIR results reveals that the Moringa oleifera seed contains various active functional groups which are appears to be played a significant role in biosorption of arsenic ions [Fig 1]. Therefore, practical and economic point of view, renewable, biodegradable and natural resources such as Moringa oleifera could be considered as affordable and technology cost effective biosorbent for the removal of arsenic from waste water by all sections of society.