Removal of hardness from drinking water by electrocoagulation using iron electrodes

In the present study laboratory studies are carried out to examine the removal of hardness by electrocoagulation process from drinking water using iron rod electrodes in batch mode. The purpose of this study was to investigate the efficiency of EC process in removal of water hardness through iron-rod electrodes in varying conditions. Experimental water sample was taken from water distribution network of local area Pune City, Maharashtra state, India. The indices for calcium and total hardness removal in pH (4.0, 7.0, and 10.0), electrical potential of 12 and 24 V and reaction times of 5 minutes to 30 minutes were measured. The maximum efficiency of hardness removal which was obtained at pH 10.0, voltage of 12 and reaction time of 60 min are equal to 98.5% and 97.5% for calcium and total hardness, respectively. Final pH of remained solution has also increased which rises with acidic pH and decreases in alcoholic pH, so the results demonstrate the direct effect of pH, potential difference and reaction time on hardness removal using EC process.

A Separation and Desalination Process for Farmland Saline-Alkaline Water

Salination poses serious hazards to farmland soil. For the purpose of solving soil salination, desalination of water sources, and other problems faced by arid areas, a separation and desalination process for farmland saline-alkaline water is proposed; a separation and desalination device based on this process is also presented and tested. Results indicate that water associated with the pretreatment device satisfied the working conditions of the composite nanofiltration (NF)-reverse osmosis (RO) membrane system. The composite NF-RO membrane system produced a better filtering effect than either the NF membrane or the RO membrane. When used for filtering saline-alkaline water, the composite NF-RO membrane system achieved a desalination rate of 96.06%, a total hardness removal rate of 98.93%, and a Cl- removal rate of 99.32%, adhering to the standard for irrigation water quality. The flashing-condensation process realized a fresh water recovery rate greater than 70%. During brine evaporation using solar salt making processes, the primary compound of crystals precipitated was NaCl (with a relative content of 93%), suggesting that the precipitates have the potential values of industrial salts. These findings offer new technical references for solving the problem of farmland irrigation water faced by saline-alkaline areas worldwide.

Experimental investigation of designed solar parabolic concentrator based desalination system for textile industry wastewater treatment

The escalation in demand for textile products increased the use of fresh water and treatment of wastewater; which escalates the search for suitable and energy-efficient technology for wastewater treatment. Solar assisted technology ( i.e. solar desalination) for the textile industry wastewater treatment is proved to be an affordable technology. The only drawback of solar desalination is its low productivity which is the major hindrance in the global acceptance of the system. In the present study, an ingenious improvement in form of a parabolic concentrator-based solar desalination system (PCB-SDS) is designed to overcome low productivity, and the simultaneous use of source textile industry wastewater for its treatment makes this study more realistic. The performance of the designed system was examined for three different brine depths i.e. 20%, 40%, and 60% for two different processing step i.e. Dyeing and Degumming. System performance was evaluated in terms of energetic, exergetic, pollutant removal, and economic analysis. The maximum output of the system was found to be around 7440 and 8330 mL/day on clear sunny days with textile dyeing wastewater (TDyWW) and textile degumming wastewater (TDgWW) at 60% depth respectively. Daily average energy and exergy efficiency of system varies in the range 39.8–51.9 and 3.6–4.8% respectively. The degumming wastewater shows 85% COD removal, whereas, around 90% of TDS and hardness removal was also recorded. The dyeing processed wastewater showed 80% COD removal efficiency, ≅90% TDS, and hardness removal. The cost per liter of distillate output produced from designed PCB-SDS was found to be 0.014 $/L.

Comparative analysis the performance of electrochemical water softening between high frequency electric fields and direct current electric fields based on orthogonal experimental methods

Electrochemical water softening has been widely used in industrial circulating cooling water systems; however, their low deposition efficiency is the main drawback that limits usage in medium to large enterprises. In this work, the effect of different parameters on the hardness removal efficiency and energy consumption of the electrochemical water softening system is experimentally studied, and the performance of water softening applied by high frequency electric fields and direct current electric fields are comparative analyzed. The impact factors of the electrochemical water softening system are as follows: initial feed concentration of solute, magnitude of voltage, inter-electrode distance, area of cathode and frequency of power supply. To improve the analysis efficiency, the L25 (55) orthogonal table is used to investigate the five different factors at five levels. The experimental results are shown that the initial feed concentration of solute is the most significant factor affecting the hardness removal efficiency. The optimal combination for water softening in the group applied by high frequency electric field and direct current electric field are A3B2C1D4E3 and A2B5C3D1 respectively. The energy utilization of the device applied by high frequency electric field is 3.2 times that applied by direct current electric field. The practice shows that direct current electric fields have a better softening effect, and are is more suitable for scaling ion removal. Particle image velocimetry (PIV) was used to observe the flow field induced by the electrolysis and found that the vertical and horizontal velocities of the flow field at low voltage are conducive to the migration of scaled ions to the cathode, and then the electrolytic reaction and deposition reaction synergy effect is the optimal.

Experimental Study on Electrochemical Softening for Cooling Circulating Water in Converter Station

In this study, the electrochemical softening method was used to treat the simulated drainage of the converter station, and the treatment effect under different water inlet conditions was investigated. The results show that the hardness removal rate is from 10% to 80% when the residence time is from 0.5h to 4h, and the longer the residence time is, the higher the removal rate is. The maximum scale removal capacity reached 2.67g/h/m2 when residence time was 1h. Through the formula fitting of several groups of tests, it is concluded that the removal effect can be expressed by the formula C0/C=0.9627e(17.73at/V) under different water intake (residence time).

An Investigation on Effectiveness of Grafted Potato Starch as an Adsorbent for Hard Water Treatment

Water is essential for the life of all living organisms. But water with very high hardness (Ca2+ and Mg2+) is harmful to health. In addition, hard water clogs the pipes in the industries. This study was conducted to investigate the effectiveness of grafted potato starch as an adsorbent for hard water treatment. Four samples of well water from Nzuguni, Ng’hong’hona, Kisasa, and Swaswa of Dodoma municipal were analyzed by the EDTA titrimetric method. The results showed the highest hardness of 547 mg/L in the water sample of Ng’hong’hona from which hardness was removed. The maximum percentage removal of 74.50% was achieved at 80 minutes of optimum contact time. The optimum adsorbent dose is 3.5 g at which 80.7% of removal was achieved. The optimum temperature was 80°C at which 75.8% of removal achieved. An increase in pH increased the percentage of removal up to a pH of 12 with 71.1%. The data obtained showed that the adsorption process fitted Langmuir type II isothermal model and pseudo-second-order kinetic model with correlation coefficients of 0.9994 and 0.9940, respectively. Grafted potato starch has shown higher efficiency in hardness removal, and hence, this adsorbent is highly recommended for the treatment of hard water.

Nano-zeolite-graphene oxide composite for calcium hardness removal: isotherm and kinetic study

The present study is an attempt to synthesize and explore the applications of the synthetic nano-zeolites (nZ) and its composites with graphene oxide (GO) for water purification. The modified Hummer's method and hydrothermal methods were applied for the synthesis of the graphene oxide and nano zeolites respectively, followed by the preparation of the composite with the ultrasonic method. Scanning electron microscopy, energy dispersive analysis of X-rays, Fourier transform infrared spectroscopy and X-ray fluorescence were used for physico-chemical characterization of the composite. The various parameters of adsorbent dose, contact time, initial and final pH of solution were optimized for the removal of calcium hardness. The results indicate optimum removal (98%) can be reached at pH 7 while the removal is highly adsorbent dose-dependent. The nZGO removal data were investigated by pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion. In that, pseudo-second-order and intraparticle diffusion models are best fitted to the experimental data. The experimental data were also analysed by Langmuir, Freundlich and Temkin isotherms, the experimental data follows the Langmuir isotherm and the determination coefficient is 0.99.