Treatment of spent brine from a nitrate exchange process using combined biological denitrification and sulfate precipitation

Abstract

A combined biological denitrification and sulfate precipitation process was developed to treat and reuse the spent brine produced by a nitrate exchange system. Although the spent brine contained a relatively high salt concentration, more than 80% of NO3(-)-N fed into the denitrification reactors was removed at a nitrate-N loading rate of 2.2 g NO3(-)-N/l x day, regardless of the presence or absence of sulfate up to 8,000 mg/l. Sulfate present in the spent brine was successfully removed by the addition of BaCl2 and the settling velocity of BaSO4 suspension was remarkably enhanced by FeCl3 coagulation. Since most of the chloride consumed in regenerating the exhausted resins was replaced during chemical treatment with BaCl2 and FeCl3, it was possible to reuse the treated spent brine as a regenerant after compensating for the small amount of unreplaced NaCl.

Nitrate and nitrite electrocatalytic reduction on Rh-modified pyrolytic graphite electrodes

“…Such a contamination can result in a high risk for public health causing bladder and ovary cancers [2][3][4][5]. Various methods such as biological, physicochemical and chemical have been proposed so far for the removal of nitrates from potable water and wastewaters [6][7][8][9][10][11]. However, they possess various disadvantages, such as a low NO 3 − destruction rate, the formation of toxic byproducts and the production of secondary brine wastes [12].…”

Cu–Ni materials prepared by mechanical milling: Their properties and electrocatalytic activity towards nitrate reduction in alkaline medium

“…Several techniques can be used for their removal, such as ion exchange, reverse osmosis and biological methods [1][2][3][4][5]. However, they encounter numerous problems due to the demand for industrial scale application and proper conditions maintenance.…”

Biological treatment of ion-exchange brine regenerant for re-use: A review

“…Despite variations in influent concentration (30 g NaCl L −1 , 0.6-1.7 g NO 3 − -N L −1 and 0.5-2.5 g SO 4 2− L −1 ) 96% removal was observed in the denitrifying reactor at a loading rate 5.4 g NO 3 − -N L −1 d −1 whereas sulphate reduction efficiency remained at ∼62% at a loading rate of 1.8 g SO 4 2− L −1 d −1 [44]. More recently, the same authors [49] explored the feasibility of sulphate sedimentation by the addition of barium chloride followed by enhanced coagulation with ferric chloride. However, chemical and capital costs pertaining to rapid mixing and separation stages probably outweigh the advantages offered.…”