Removal of contaminants from water
Overburden from surface coal mining in many regions can produce a rain runoff laden with selenium, in the selenate form. This occurs from rainwater leaching through exposed selenium-containing rocks in the overburden. The selenium-containing runoff water is caught in ponds. Remediation of the pond water to remove selenate is performed by treatment with sulfur-modified iron (SMI) in a contact bed of an upflow reactor vessel. The pond water after pretreatment is pumped through the SMI reactor, and can then be run through an oxidation tank and filtered to remove iron. For extending effectiveness and life of the SMI the contact bed is either periodically “fluffed” with a high-velocity upflow of water through the bed, or moved continuously through the column in a continuous medium filtration system. A biocide can be added to runoff water prior to the contact bed.
1. A method for removal of contaminants from contaminated water, comprising:
prefiltering the contaminated water to remove particulate material, if suspended particulate material is present,
assuring pH of the prefiltered contaminated water is within a range of about pH 5.0 to about pH 7.0, and adjusting pH of the contaminated water when necessary,
pumping the contaminated water in upflow direction through a reactor column, in a vessel containing a contact bed of SMI which the contaminated water contacts, thereby removing a significant portion of dissolved contaminants from the water, to produce a treated water, and
the reactor column being a continuously moving medium wherein the medium comprises SMI, with the SMI continuously moving down in the reactor column to a bottom wherein particles of SMI are raised upward with water through an uplift column and then deposited back onto the top of the contact bed, thereby preventing compacting and maintaining looseness in the SMI bed.
2. The method of claim 1 , wherein the prefiltering step includes filtering the contaminated water with a sand filter followed by an activated carbon filter.
3. The method of claim 1 , wherein the pH of the contaminated water is adjusted to a range of about pH 6.0 to pH 6.5.
4. The method of claim 1 , further including adding a biocide into the contaminated water in a concentration effective to reduce biofilm-producing microbes in the contaminated water.
5. The method of claim 1 , further including removing from the treated water iron which has been introduced into the water by contact with the SMI.
6. The method of claim 5 , wherein the iron removal step includes oxidation of the treated water to oxidize iron and form a precipitate, then a post-filtering step in which iron oxides are filtered out of the water.
7. The method of claim 1 , wherein the contaminated water includes selenium, which is removed by the contact bed of SMI.
8. The method of claim 7 , wherein the contaminated water is refinery water.
9. The method of claim 1 , wherein the contaminated water is heavy metal-contaminated ground water.
10. A system for removing selenium from contaminated water used in industry or for domestic water, comprising:
a treatment plant receiving a flow of said contaminated water and for removing selenium from the contaminated water,
the treatment plant including a means for adjusting pH of the contaminated water as necessary to place the acidity of the contaminated water in a range of about pH 5.0 to pH 7.0, and a reactor column downstream of the pH adjustment means and receiving the contaminated water, the reactor column comprising a vessel containing a contact bed of SMI for contact with the contaminated water, and a pump for passing the contaminated water through the reactor column in an upflow direction, the reactor column being effective to remove a significant portion of selenium contained in the contaminated water to produce a treated water, and
wherein the reactor column is a continuously moving medium wherein the medium comprises SMI, with the SMI moving in a continuous loop down in the reactor column to a bottom wherein particles of SMI are raised upward with water through an uplift column and then deposited back onto the top of the contact bed, thereby preventing compacting and maintaining looseness in the SMI bed.
11. The system of claim 10 , wherein said flow of contaminated water comprises refinery water.
12. A system for removing selenium from contaminated water used in industry, comprising:
a treatment plant receiving a flow of said contaminated water and effective to remove selenium from the contaminated water,
the treatment plant including a means for adjusting pH of the contaminated water as necessary to place the acidity of the contaminated water in a range of about pH 5.0 to pH 7.0, and a reactor column downstream of the pH adjustment means and receiving the contaminated water,
the reactor column comprising a continuously moving medium vessel containing a contact bed of SMI as a medium for contact and reaction with the contaminated water, and a pump for passing the contaminated water through the reactor column in an upflow direction, the reactor column being effective to remove a significant portion of selenium contained in the contaminated water to produce a treated water, and the moving medium vessel defining a continuous loop, moving the SMI down by gravity in the reactor column to a bottom wherein particles of SMI simultaneously are raised upward through an uplift column and then deposited back onto the top of the contact bed to thereby prevent compacting and maintain looseness in the SMI bed.