Selenium removal process

Claim 2

A process comprising the steps of: (a) contacting a compound selected from the group having the formula X(ZO.sub.a).sub.b, Q.sub.m O.sub.n, ClO.sub.3, Cl.sub.2 O.sub.6, Br.sub.3 O.sub.8, I.sub.2 O.sub.5, and mixtures thereof with a selenium-containing waste water having (i) a chemical oxygen demand of at least about 25 mg oxygen/l and (ii) at least a portion of the selenium content present in a valence state of less than +4 to form a Se +4 -containing pretreated waste water; and (b) removing at least about 50 percent of the selenium content from the Se +4 -containing pretreated waste water, wherein X is a cation; Z is halogen selected from the group consisting of chlorine, bromine, and iodine; a is an integer from 1-3; b is an integer equal to the valence of X; Q is chlorine or bromine; and m and n are each 1 or 2, provided than m+n equals 3.

Claim 3

The process of claim 1 wherein the compound has the formula X(ZO.sub.a).sub.b and X is selected from the group consisting of alkali metals and alkaline-earth metals; and Z is a halogen selected from the group consisting of chlorine and bromine.

Claim 4

The process of claim 2 wherein X is selected from the group consisting of sodium, potassium, calcium, and magnesium.

Claim 5

The process of claim 1 wherein the compound has the formula NaClO a .

Claim 6

The process of claim 1 wherein the compound has the formula NaClO.

Claim 7

The process of claim 1 wherein the selenium-containing waste water has a pH of at least about 6.

Claim 8

The process of claim 1 wherein the selenium-containing waste water has a pH of at least about 7.

Claim 9

The process of claim 1 wherein the selenium-containing waste water has a pH of about 7.5 to about 8.5.

Claim 10

The process of claim 1 wherein the selenium-containing waste water is contacted with a sufficient amount of the compound for the Se +4 -containing pretreated waste water to have a Se +4 concentration at least about 50 percent greater than the Se +4 concentration in the selenium-containing waste water.

Claim 11

The process of claim 1 wherein the selenium-containing waste water is contacted with a sufficient amount of the compound for the Se +4 -containing pretreated waste water to have a Se +4 concentration at least about 75 percent greater than the Se +4 concentration in the selenium-containing waste water.

Claim 12

The process of claim 1 wherein the selenium-containing waste water is contacted with a sufficient amount of the compound for the Se +4 -containing pretreated waste water to have a Se +4 concentration at least about 85 percent greater than the Se +4 concentration in the selenium-containing waste water.

Claim 13

The process of claim 1 wherein the selenium-containing waste water further comprises at least one non-selenium containing substance capable of being oxidized by the compound.

Claim 14

The process of claim 1 wherein step (b) comprises removing at least about 75 percent of the selenium content from the Se +4 -containing pretreated waste water.

Claim 15

The process of claim 1 wherein step (b) comprises removing at least about 85 percent of the selenium content from the Se +4 -containing pretreated waste water.

Claim 16

The process of claim 1 wherein step (b) comprises removing at least about 90 percent of the selenium content from the Se +4 -containing pretreated waste water.

Claim 17

The process of claim 1 wherein the selenium-containing waste water is contacted with a sufficient amount of the compound for the Se +4 -containing pretreated waste water to have a Se +4 concentration at least about 90 percent greater than the Se +4 concentration in the selenium-containing waste water.

Claim 18

A process comprising the steps of: (a) introducing oxygen into a selenium-containing waste water having (i) a chemical oxygen demand of at least about 25 mg oxygen/l and (ii) at least a portion of the selenium content present in a valence state of less than +4 to form an oxidized selenium-containing waste water having at least a portion of the selenium content still present in a valence state of less than +4; (b) combining the oxidized selenium-containing waste water with another waste water to form a combined selenium-containing waste water having at least a portion of the selenium content present in a valence state of less than +4; (c) contacting a compound selected from the group having the formula X(ZO.sub.a).sub.b, Q.sub.m O.sub.n, ClO.sub.3, Cl.sub.2 O.sub.6, Br.sub.3 O.sub.8, I.sub.2 O.sub.5, and mixtures thereof with the combined selenium-containing waste water to form a Se +4 -containing pretreated waste water; and (d) removing at least about 50 weight percent of the selenium content from the Se +4 -containing pretreated waste water.

Claim 19

A process comprising the steps of: (a) introducing oxygen into a selenium-containing waste water having (i) a chemical oxygen demand of at least about 25 mg oxygen/l and (ii) at least a portion of the selenium content present in a valence state of less than +4 to form an oxidized selenium-containing waste water having at least a portion of the selenium content still present in a valence state of less than +4; (b) combining the oxidized selenium-containing waste water with another waste water to form a combined selenium-containing waste water having at least a portion of the selenium content present in a valence state of less than +4; (c) contacting a compound selected from the group having the formula X(ZO.sub.a).sub.b, Q.sub.m O.sub.n, ClO.sub.3, Cl.sub.2 O.sub.6, Br.sub.3 O.sub.8, I.sub.2 O.sub.5, and mixtures thereof with the combined selenium-containing waste water to form a Se +4 -containing pretreated waste water; and (d) removing at least about 50 weight percent of the selenium content from the Se +4 -containing pretreated waste water.

Claim 20

The process of claim 17 wherein step (d) comprises removing at least about 75 percent of the selenium content from the Se +4 -containing pretreated waste water.

Claim 21

The process of claim 17 wherein step (d) comprises removing at least about 85 percent of the selenium content from the Se +4 -containing pretreated waste water.

Claim 22

The process of claim 17 wherein step (d) comprises removing at least about 90 percent of the selenium content from the Se +4 -containing pretreated waste water.