Environmental Threat
Site Characterization
Man. Gas Processes
Plant Wastes
Contamination Threat Modes
Residuals - Components
Sources of MGP Liquid Effluent
FMG Plants in the US
Parallel MG Technologies
Think you've found a gas works?
Locating and Confirming a Site
Locations of US Gas Plants
FMGP In The News
FMGP In The Arts
Coal-tar Site Litigation
Related sites on the Internet
Literature of Manufactured Gas
Hatheway Harangues
Publications by Dr. Hatheway
Slide Shows by Dr. Hatheway
Slide Shows by others
Hatheway Bio
Hatheway Resume
Legal Considerations


Sources of Manufactured Gas Plant Liquid Effluent

Each component of a manufactured gas plant, and associated works, generated, collected and or utilized wasters of condensation, as well as clear, cool local makeup waters for the purpose of “clarification”, or removal of tar particles from the gas produced for sale. Such effluents bore PAHs (along with MAHs and DAHs) through the entire gas making, storage and distribution processes. Except at exceptional gas works equipped with ammoniacal liquor distillation for ammonia by-product recovery, these effluents were considered as wastes and managed through a variety of options available to the gas plant management. Foremost among the options was discharge to the ground. 





Coal Gas Retorts (Ammoniacal Liquor)

Became Clarification Water

Entire History

Expect evidence of operational-era leakage at each gas-plant production component and along each pipe flow path from retort to gas holder

Quench Water at
Coal-Gas Coke and
By-Product Coke-

Cool, Clear Water Sprayed at Retort Floor or on hot coke car

Entire History

Collected in a floor channel against the retort bench front on the retort house floor, then channeled to the plant sewer for subsequent real- time discharge.  At coke ovens, originally sent to waste lagoon or discharged to open drainage; after ca. 1920 to cooling ponds, for re-use.

Clarification Waters
(At all Components, Condenser to Purifiers)

Required Cool and Reasonably Clear Water to Drop Tar

Entire History

Made up of waters of condensation released with the gas at all types of gas machines then carried to and through the clarification process. After ca.1890, some plants had quasi-separate systems in which clear, cool water would be added at individual clarification devices, all to enhance removal of tar, ammonia, and other detrimental residuals. Ultimate fate was discharge to the plant sewer or to the ground, as an option of plant management.

Clarification Device Sumps
  - Condenser
  - Washer
  - Scrubber
  - Washer-Scrubber

Used Make-up Water

Began with  condenser use
 ca. 1812.
 Others after ca. 1890

Sumps became design features to collect tar (PAH) globules and particles and to pass the remainder of the condensation effluent. Sumps were hand-cleaned or pumped and tar managed in accordance with plant directive.  The portion of the collected residuals represented by tar sludges generally was considered waste.

Carburetted Water Gas
  (Gas Liquor)
Tar-Water Emulsions

Reached as High as 90% of

Began about 1910

Emulsions came from undesirable use of heavy or crude oil and bituminous coal, in contravention to conventional wisdom but in response to market conditions of the time.  Dumping to the ground was common at gas works where evidence of dehydration equipment is not found today. Usually found as disposed to tar “ponds” or “lagoons.”

Purifier-Box Gas Liquor Collection and Overflow

Constant Release of Collected Moisture

Always Present

Gravity collection in box bottoms and drained to discharge in accordance with plant directives.
Today, most purifier-box locations are hotspots on this account.

Gas Holder Water-Seal

Constant Flow Through Walls of Subsurface Tanks (where present)

Always Present in Pit-Type Holders

Operational-era outward leakage of light and medium oils from pit-type gas holders, through rendering, bricks, puddle and dumplings, and into surrounding soil, and contact with ground water, where present.

Tar Separators
(Underground Types)

- Wooden Construction

- Concrete


Less Common

General use began about 1890

Operational-era outward leakage of gas liquor minus what tar globules were separated and retained. Effluent still carried MAH/DAH/PAH as TDS and microparticles.

“Sediment” Basins

Sprayed Effluent


In response to recommendations of AGA Committee on Gas House Wastes (1920s).

Gas Liquor Centrifuges

Dewatering of Tar-Water Emulsions


Koppers Corp., in response to equipment recommendations of AGA Committee on Gas House Wastes.



ca. 1910

Corps of Engineers restriction on dumping of lamp black into Willamette River at Portland, OR (1906) led to creation of lampblack recovery and conversion to fuel briquettes. Many other plants continued to dump this waste, often containing PAHs.

Gasyard Drips

As Leaks

ca. 1840

Collected light-oil and the condensates along gasyard and distribution lines;  Prone to leak to environment during the operational life of the gas works.

Benzol Plants at
By-Product Ovens and
MGP Plants

Prepared Raw Benzol

From 1914

Benzol used as "motor spirits" for vehicle fuel.  Major British and U.S. program in WWI for munitions recovery of toluene as a benzol constituent Processing collected and released effluent waters.


Copyright 2020-25  by Dr. Allen W. Hatheway    All rights reserved.
Individuals and organizations (Governmental, Corporate, Public Interest, Publishing Authors and The Media) wishing to make use of the contents, either for scholarly research, publication of any form, hardcopy or electronic, news media copy, and for various commercial purposes, such as website offerings of services, are herewith cautioned to make appropriate quotes of www.hatheway.net as the source of such materials, including the date upon which such materials were transferred to the above-stated personal or corporate use and to so inform Dr. Hatheway, electronically, as a courtesy.  Professor Hatheway's offerings, constituting this website, are further subject to the Copyright & Legal Considerations appearing on the webpage by that name. For further information on Former Manufactured Gas Plants and related topics, please contact Dr. Hatheway at allen@hatheway.net