Abstract
It is a great advantage to reduce the energy requirement for the provision of consumable groundwater to an absolute minimum. Reverse osmosis (RO) and nanofiltration (NF) are two of the most commonly used technologies for desalination water to provide potable water with lowest energy consumption. However, there is still lack of a thorough comparison between these two methods providing the better option in different conditions. Therefore, in this paper, nitrate rejection and the effects of operation conditions on the performance of RO and NF systems are compared. Several wells in Zarch District, Iran, are polluted by nitrate and groundwater is a major drinking water source in the region. The aim of this research was to evaluate the efficiency of nitrate removal by two commercial membranes NF90 and BW30 (both Dow Filmtec) using natural water under different operating conditions. Experiments were conducted to assess the influence of temperature and pressure on nitrate removal by the membranes. The results indicated that BW30 (reverse osmosis) performs better removing nitrate than NF90 (Nano-filter). With a feed of 200 mg-NO3-.L-1 (as nitrate), only permeate from the BW30 membrane met the required quality standard for drinking purposes (50 mg-NO3-.L-1). When the feed concentration increased to 250 mg-NO3-.L-1, both membranes failed to achieve the standard in the permeate. The membranes showed similar nitrate removal behaviour under different applied temperatures and pressures. It was concluded that the BW30 membrane can be used to produce drinking water in the study area with influent concentrations below 200 mg-NO3.L-1.
Highlights
Water is the main vital factor not for humans but every living organism
Similar nitrate removal performance has been reported for the BW30 membrane, with 85% nitrate rejection achieved using a model solution (Richards et al, 2010)
Rejection declined from 86.4 to 70.4% and 90.7 to 73.1% for NF90 and BW30 membranes, respectively, as the feed concentrations increased from 50 to 300 mg-NO-3.L-1. Both membranes showed a strong relationship between nitrate removal and feed nitrate concentration for all conditions applied
Summary
Water is the main vital factor not for humans but every living organism. Substantial researches have been dedicated to the development of methods for the revival, rejuvenation, and conservation of water resources with minimum cost and energy consumption. Nitrate is one of the most important polluting factors which should be removed from drinking water with an optimum amount of energy. The groundwater in Zarch District, Iran, is contaminated with nitrate but is a major drinking water resource. According to the most recent census, the area has a population of around 20,000 with poor access to clean water (Statistical Center of Iran, 2011). Groundwater management is a challenge for the local water supply authority, which has to deal with around 4,000 households mainly classified as rural settlements in the region. It is estimated that about 2880 l.d-1 is required, as average domestic water usage per capita is 13.48 l.d-1
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