Optimization of Nitrate Removal Efficiency and Energy Consumption Using a Batch Monopolar Electrocoagulation: Prediction by RSM Method

Due to the extensive application of artificial nitrogen-based fertilizers on land, groundwater from the central part of Taiwan faces problems of increasing concentrations of nitrate, which were measured to be well above 30 mg/L all year round. For meeting the 10 mg/L nitrate standard, optimal operations for a heterotrophic denitrification pilot plant designed for drinking water treatment was investigated. Ethanol and phosphate were added for bacteria growing on anthracite to convert nitrate to nitrogen gas. Results showed that presence of high dissolved oxygen (around 4 mg/L) in the source water did not have a significantly negative effect on nitrogen removal. When operated under a C/N ratio of 1.88, which was recommended in the literature, nitrate removal efficiency was measured to be around 70%, sometimes up to 90%. However, the reactor often underwent severe clogging problems. When operated under C/N ratio of 1.0, denitrification efficiency decreased significantly to 30%. Finally, when operated under C/N ratio of 1.5, the nitrate content of the influent was almost completely reduced at the first one-third part of the bioreactor with an overall removal efficiency of 89–91%. Another advantage for operating with a C/N ratio of 1.5 is that only one-third of the biosolids was produced compared to a C/N value of 1.88.

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Biogeochemical indicators to evaluate pollutant removal efficiency in constructed wetlands

Water Science & Technology ◽

10.2166/wst.1997.0152 ◽

1997 ◽

Vol 35 (5) ◽

pp. 1-10 ◽

Cited By ~ 53

Author(s):

K. R. Reddy ◽

E. M. D'Angelo

Keyword(s):

Microbial Biomass ◽

Removal Efficiency ◽

Nitrate Removal ◽

Oxygen Demand ◽

Acid Soils ◽

Pollutant Removal ◽

Alkaline Soils ◽

Organic C ◽

Wetland Treatment ◽

Biogeochemical Indicators

Wetlands support several aerobic and anaerobic biogeochemical processes that regulate removal/retention of pollutants, which has encouraged the intentional use of wetlands for pollutant abatement. The purpose of this paper is to present a brief review of key processes regulating pollutant removal and identify potential indicators that can be measured to evaluate treatment efficiency. Carbon and toxic organic compound removal efficiency can be determined by measuring soil or water oxygen demand, microbial biomass, soil Eh and pH. Similarly, nitrate removal can be predicted by dissolved organic C and microbial biomass. Phosphorus retention can be described by the availability of reactive Fe and Al in acid soils and Ca and Mg in alkaline soils. Relationships between soil processes and indicators are useful tools to transfer mechanistic information between diverse types of wetland treatment systems.

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Simultaneous oxidation and reduction treatments of polluted water by a bio-electro reactor

Water Science & Technology ◽

10.2166/wst.1996.0187 ◽

1996 ◽

Vol 34 (9) ◽

pp. 101-108 ◽

Cited By ~ 11

Author(s):

M. Kuroda ◽

T. Watanabe ◽

Y. Umedu

Keyword(s):

Aqueous Solution ◽

Organic Matter ◽

Electric Current ◽

Removal Efficiency ◽

Concentration Ratio ◽

Nitrate Removal ◽

Hydrogen Gas ◽

Polluted Water ◽

Simultaneous Oxidation ◽

Denitrifying Microorganisms

Application of a bio-electro reactor for treatment of various kinds of polluted water was investigated experimentally. Aqueous solution of nitrate, ammonium and/or organic matter were used as synthetic polluted water. Denitrification of the nitrate polluted water without organic matter proceeded effectively by utilizing hydrogen gas produced by electrolysis of water in the reactor. The bio-electro reactor was also available for the treatment of nitrate polluted water containing organic matter when the C/N concentration ratio was up to 1.0 under the condition of 100 mA of applied electric current. The nitrate removal efficiency from nitrate polluted water containing acetate at C/N=1.0 was more than 90% at 5 hours of HRT and 80% even at 2.8 h HRT. For the treatment of ammonium polluted water, nitrification and denitrification proceeded simultaneously in a bio-electro reactor where nitrifying and denitrifying microorganisms were immobilized on the electrodes. The results obtained in this study suggested that the bio-electro reactor system was capable to application for oxidation and reduction treatments of the nitrate and ammonium polluted water.

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Copper and Lead Ions Removal by Electrocoagulation: Process Performance and Implications for Energy Consumption

International Journal of Renewable Energy Development ◽

10.14710/ijred.2021.31665 ◽

2021 ◽

Vol 10 (3) ◽

pp. 415-424

Author(s):

Aji Prasetyaningrum ◽

Dessy Ariyanti ◽

Widayat Widayat ◽

Bakti Jos

Keyword(s):

Heavy Metals ◽

Energy Consumption ◽

Removal Efficiency ◽

Current Density ◽

High Current Density ◽

Energy Requirement ◽

Lead Ions ◽

Initial Concentration ◽

Electroplating Wastewater ◽

Electrocoagulation Process

Electroplating wastewater contains high amount of heavy metals that can cause serious problems to humans and the environment. Therefore, it is necessary to remove heavy metals from electroplating wastewater. The aim of this research was to examine the electrocoagulation (EC) process for removing the copper (Cu) and lead (Pb) ions from wastewater using aluminum electrodes. It also analyzes the removal efficiency and energy requirement rate of the EC method for heavy metals removal from wastewater. Regarding this matter, the operational parameters of the EC process were varied, including time (20−40 min), current density (40−80 A/m2), pH (3−11), and initial concentration of heavy metals. The concentration of heavy metals ions was analyzed using the atomic absorption spectroscopy (AAS) method. The results showed that the concentration of lead and copper ions decreased with the increase in EC time. The current density was observed as a notable parameter. High current density has an effect on increasing energy consumption. On the other hand, the performance of the electrocoagulation process decreased at low pH. The higher initial concentration of heavy metals resulted in higher removal efficiency than the lower concentration. The removal efficiency of copper and lead ions was 89.88% and 98.76%, respectively, at 40 min with electrocoagulation treatment of 80 A/m2 current density and pH 9. At this condition, the speciﬁc amounts of dissolved electrodes were 0.2201 kg/m3, and the energy consumption was 21.6 kWh/m3. The kinetic study showed that the removal of the ions follows the first-order model.

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