Method and apparatus for biologically treating coking-plant wastewater

Patent metadata

Field	Value
Publication number	US-9284204-B2
Application number	US-201214000909-A
Country	US
Kind code	B2
Filing date	Apr 2, 2012
Priority date	Apr 11, 2011
Publication date	Mar 15, 2016
Grant date	Mar 15, 2016

Abstract

The invention relates to a process for the biological purification of coking plant wastewater that is loaded with nitrogen compounds, cyanides, phenols and sulphides. The coking plant wastewater, for removal of pollutants that inhibit a nitrification, is fed together with a biomass-containing stream of matter to a detoxification reactor that has a gas-treatment zone and a reaction zone. The feed mixture supplied to the detoxification reactor is exposed in the gas-treatment zone to a gaseous oxidizing agent. A stream of matter enriched with the oxidizing agent is fed to the reaction zone in which cyanides and other pollutants inhibiting the nitrification are biodegraded. A stream of matter is withdrawn from the reaction zone and returned to the detoxification reactor. In addition, a wastewater stream from the detoxification reactor is separated by a membrane filtration into a biomass-containing retentate stream and a purified permeate stream. From the retentate stream, a substream which entrains excess sludge is discharged. The retentate stream, after separating off the substream, is recirculated to the detoxification reactor. The permeate stream is further purified by nitrification and subsequent denitrification.

First claim

The invention claimed is:

1. A method of biologically treating coking-plant wastewater contaminated with nitrogen compounds, cyanides, phenols and sulfides, the method comprising the steps of:
for removing nitrification-inhibiting pollutants, mixing the coking-plant wastewater with a biomass-containing material and feeding the mixture of wastewater and biomass to a detoxification reactor having a gas-exposure zone and a reaction zone,
exposing the mixture fed to the detoxification reactor to a gaseous oxidizing agent in the gas-exposure zone and feeding the resultant mixture with the oxidizing agent to the reaction zone where cyanide and other nitrification-inhibiting pollutants are degraded so as to detoxify the mixture,
drawing off a portion of the detoxified mixture from the reaction zone and recirculating the drawn-off portion to the detoxification reactor,
separating a stream of the detoxified mixture from the detoxification reactor by membrane filtration into a biomass-containing retentate stream and a treated permeate stream,
extracting excess sludge from the retentate stream and recirculating the resultant sludge-free retentate stream to the detoxification reactor, and
treating the permeate stream by nitrification and subsequent denitrification.

2. The method according to claim 1 , further comprising the step of:
using activated sludge from municipal treatment plants adapted over several weeks to coking-plant wastewater as biomass for the operation of the detoxification reactor.

3. The method according to claim 1 , wherein the nitrification is effected in a nitrification reactor that includes a gas-exposure zone and a reaction zone, the method further comprising the steps of:
recirculating a stream from the reaction zone of the nitrification reactor to the gas-exposure zone of the nitrification reactor and concentrating the recirculated stream therein with the gaseous oxidizing agent and the permeate stream,
circulating a further stream from the reaction zone of the nitrification reactor of the nitrification reactor to a settling basin operated as denitrification means,
recirculating a biomass-entraining stream from the denitrification means to the nitrification reactor, and
drawing off a biologically treated stream of wastewater from the denitrification means.

4. The method according to claim 1 , further comprising the step of:
connecting the reaction zone and the gas-exposure zone of the detoxification reactor and/or the nitrification reactor by a nozzle where fluid is introduced from the inflow to the gas-exposure zone such that flow generated in the nozzle entrains fluid from the reaction zone.

5. The method according to claim 3 , further comprising the step of:
branching off a partial stream from the permeate stream downstream of the detoxification reactor during membrane filtration and recirculating it to the denitrification step directly.

6. The method according to claim 3 , further comprising the step of:
post-treating the stream of wastewater by membrane filtration.

7. The method according to claim 6 , further comprising the steps of:
separating the stream of wastewater into a biomass-containing retentate stream and a treated permeate stream,
extracting a partial stream entraining excess sludge from the retentate stream, and,
following separation of the partial stream, recirculating the retentate stream to the denitrification step.

8. The method according to claim 1 , further comprising the steps of:
using modules with fluid-flooded membranes for the membrane filtration step, and
adjusting an overflow rate on the membranes by the rate of fluid flow circulated in the system.

9. The method according to claim 8 , wherein ultrafiltration membranes are used for the membranes.

10. An apparatus for biologically treating coking-plant wastewater contaminated with nitrogen compounds, cyanides, phenols and sulfides, the apparatus comprising:
a detoxification reactor including an upper reaction zone, a lower gas-exposure zone with a supply means for a gaseous oxidizing agent, and means for recirculating fluid from the reaction zone to the gas-exposure zone for removing nitrification-inhibiting pollutants,
a device for membrane filtration of a stream of wastewater pretreated in the detoxification reactor, and
a device including a nitrification reactor having an upper reaction zone, a lower gas-exposure zone with supply means for a gaseous oxidizing agent, and means for recirculating fluid from the reaction zone to the gas-exposure zone for biological wastewater treatment of a permeate stream occurring during nitrification and denitrification.

11. The apparatus according to claim 10 , further comprising:
respective loops for circulating fluid in the reaction zone and in the gas-exposure zone of the detoxification reactor or the nitrification reactor, and
a nozzle between the two zones where recirculated fluid from the coking-plant wastewater or a pretreated stream of wastewater from the detoxification reactor entrains fluid from the upper loop conveying it to the gas-exposure zone.

12. The apparatus according to claim 10 , further comprising:
a settling basin operated as a denitrification means downstream of the nitrification reactor such that a biomass-containing stream can be recirculated from the settling basin to the nitrification reactor.

13. The apparatus according to claim 12 , further comprising:
a membrane filtration means for treating a stream of wastewater drawn off from the settling basin downstream of the denitrification step.

Assignees

• Thielert Holger
• Thyssenkrupp Uhde Gmbh

Inventors

• Thielert Holger

Classifications

• C02F3/1268

  Membrane bioreactor systems · CPC title

• C02F2103/365

  from petrochemical industry (e.g. refineries) · CPC title

• C02F3/1278

  Provisions for mixing or aeration of the mixed liquor · CPC title

• Y02W10/15

  Cross-Sectional Technologies · mapped topic

• C02F3/302 Primary

  Nitrification and denitrification treatment (C02F3/308 takes precedence) · CPC title