Apparatus and Method for Treating Fgd Blowdown or Similar Liquids

• US 20080257820A1
• Filed: 07/24/2006
• Published: 10/23/2008
• Est. Priority Date: 07/25/2005
• Status: Active Grant

• Current Assignee: Zenon Technology Partnership
• Original Assignee: Zenon Technology Partnership
• Inventors: Cote, Pierre Lucien, Husain, Hidayat, Pickett, Timothy Michael, Peeters, Jeffrey Gerard, Bonkoski, William A.
• Granted Patent: US 7,790,034 B2
• Time in Patent Office: Days
• US Class Current: 210/605
• CPC Class Codes: C02F 2003/003 using activated carbon or the like
• CPC Class Codes: C02F 2101/101 Sulfur compounds
• CPC Class Codes: C02F 2101/106 Selenium compounds
• CPC Class Codes: C02F 2101/20 Heavy metals or heavy metal compounds
• CPC Class Codes: C02F 2103/18 from the purification of gaseous effluents
• CPC Class Codes: C02F 2209/04 Oxidation reduction potential [ORP]
• CPC Class Codes: C02F 3/006 Regulation methods for biological treatment
• CPC Class Codes: C02F 3/06 using submerged filters
• CPC Class Codes: C02F 3/302 Nitrification and denitrification treatment C02F3/308 takes precedence
• CPC Class Codes: Y02E 50/30 Fuel from waste, e.g. synthetic alcohol or diesel
• CPC Class Codes: Y02W 10/10 Biological treatment of water, waste water, or sewage
• CPC Class Codes: Y10S 210/903 Nitrogenous
• CPC Class Codes: Y10S 210/912 Heavy metal
• CPC Class Codes: Y10S 210/914 Mercury

Abstract

A process has steps of one or more of aerobic treatment to remove COD and nitrify a waste stream, anoxic treatment to denitrify a waste stream, anoxic treatment to remove selenium and anaerobic treatment to remove heavy metals and sulphur. The process may be used to treat, for example, FGD blow down water. The process may further include one or more of (a) membrane separation of the waste stream upstream of the anoxic digestion to remove selenium, (b) dilution upstream of the biological treatment step, (c) physical/chemical pretreatment upstream of the biological processes or dilution step to remove TSS and soften the waste stream, or (d) ammonia stripping upstream of the biological treatment steps or dilutions step. These processes may be provided in a variety of suspended growth or fixed film reactors, for example a membrane bioreactor or a fixed film reactor having a GAC bed. Processes for biological treatment of inorganic compounds in a fixed medium reactor is described including steps of one or more of maintaining desired ORP levels, optionally by controlling nutrient addition, and removing solids or gas bubbles from the medium bed.

Claims

1. A process having steps of anoxic treatment to denitrify a waste stream followed by anoxic treatment to remove selenium.

2. The process of claim 1 further comprising a step of anaerobic treatment to remove heavy metals, for example arsenic, mercury, or sulphur.

3. The process of claim 1 further comprising a step of aerobic treatment to remove COD from or nitrify the waste stream upstream of the steps of claim 1.

4. The process of claim 1 further comprising one or more steps of:

a) membrane separation of the waste stream upstream of the step of anoxic digestion to remove selenium;

b) dilution upstream of the digestion steps;

or

c) physical/chemical pretreatment upstream of the digestion steps or the dilution step to remove TSS and soften the waste stream.

5. The process of claim 1 wherein ORP of the waste stream upstream of the anoxic treatment step to denitrify is maintained between +100 and 0 mV and ORP of the waste stream downstream of the anoxic treatment step to remove selenium is maintained below 0 mV.

6. The process of claim 1 wherein ORP of the waste stream leaving the process has an ORP of −

50 mV or less.

7. The process of claim 5 wherein ORP is maintained by controlling the place or rate of a nutrient feed to the process.

8. The process of claim 1 further comprising accounting for the presence of DBA in the waste stream in determining a rate of carbon nutrient addition.

9. The process of claim 1 wherein the anoxic treatment steps occur in a fixed film bioreactor.

10. An apparatus having one or more reactors configured to provide denitrification and selenium removal by biological treatment.

11. The apparatus of claim 10 wherein the one or more reactors further provide aerobic treatment of COD by biological treatment.

12. The apparatus of claim 10 wherein the one or more reactors further provide heavy metal or sulfur removal by biological treatment.

13. The apparatus of claim 10 wherein one of the one or more reactors is a membrane bioreactor.

14. The apparatus of claim 10 wherein one of the reactors is a fixed film reactor

15. The apparatus of claim 14 wherein the fixed film reactor has an activated carbon bed used to support a population of microbes.

16. The apparatus of claim 10 having one or more of an inlet for diluting the feed water to the reactors, a system for adding lime or sulfides to the wastewater upstream of the reactors, a precipitate remover, or an ammonia stripper.

17. A process for operating a media bed reactor comprising a step of considering the oxygen reduction potential of water entering into or exiting from a part of the reactor in determining a nutrient addition amount, location or rate.

18. The process of claim 17 wherein the ORP of an upstream portion of the reactor is maintained at between 100 and 0 mV.

19. The process of claim 17 wherein the ORP of a downstream portion of the reactor is maintained at an ORP of −

50 mV or less.

20. The process of claim 17 used to remove nitrates.

21. The process of claim 17 used to remove selenium.

22. A process for operating a fixed media bioreactor comprising a step of bumping the reactor at least once per week to release solids or gas bubbles.