Celanese improves anaerobic digester Anaerobic digestion to dispose of petrochemical wastes has long been a problem because toxic materials and high pH kill the bacteria needed for effective operation of the system.

Celanese thinks it has solved the problem at several petrochemical plants along the Qulf Coast including its guar manufacturing plants in Vernon, Tex., where the wastewater contains, among other things, pro­pylene glycol and caustic soda. The answer is relatively simple—feed some of the treated effluent back into the system to dilute the toxic con­stituents and lower the pH before the water gets to the anaerobic filter.

Anaerobic digestion is essentially the decomposition of organic wastes by bacteria in the absence of air. In the process gases are given off— methane and carbon dioxide, espe­cially. The methane is used to heat the sludge to speed up decomposition. At the Celanese plant, the off-gases contain more than 72% methane.

Airco plans to sell its fen About one year after its takeover by BOC International, the U.K. indus­trial gases giant, Airco has signed agreements with a West German chemical and metals company, a U.S. trading company, and a former Airco executive to divest all its important ferroalloys business. In essence, Airco is letting go of 20 to 25% of its total sales, or well over $200 million in 1978.

Among other consequences, this divestment carves up Airco's sub­stantial position as a U.S. ferroalloys producer. This could further weaken the U.S. ferroalloys industry, which has had a rough time in the past few

The Celanese process was de­scribed by Enrique R. Witt of Cela­nese Chemical and Thomas E. Rob­erts of Celanese Polymer Specialties at the Purdue University Industrial Waste Conference at West Lafayette, Ind. The process has averaged 60% long-term chemical oxygen demand (COD) removal since the process was started up in June 1977. The facility is designed for 65% COD removal, but production formula changes at the guar plant have changed the relative mix of organics in the wastewater from what the process was designed to handle.

The facility has a design capacity of 250,000 gal per day of raw waste and 36,000 lb per day of COD. By 1980 the capacity of the anaerobic system will be expanded as the guar plant is ex­panded, so that it can handle up to 500,000 gal per day of wastewater and 55,000 lb per day of COD.

Total treatment costs for the an­aerobic system in 1978 totaled nearly $27,000. It is a net energy producer, a fact that helps cut the cost of treat­ment. Last year it generated more than 10.6 billion Btu. •

>alloys units years against rising imports, espe­cially from South Africa. South Afri­can producers, including Union Car­bide, have a strong production ad­vantage from the proximity of ore resources and from more efficient technology.

Airco says that it cannot put a final purchase price on these transactions, which will depend on assets valuation at the closing time. However, the company says that the sales would reduce BOC International's borrow­ings nearly $160 million. This sum includes proceeds already received from the sale in February 1979 of Airco's ferroalloys plant in Mobile,

Ala., to Compania Miner Autlan, a minerals firm based in Mexico City.

A number of hurdles lie ahead be­fore all parts of the divestment can be completed. Airco says that U.S. an­titrust enforcement agencies will have to look over the agreements. In addi­tion, other conditions, permits, and approvals must be satisfied.

One of Airco's new agreements is for sale of ferroalloys plants in Niag­ara Falls, N.Y., and Calvert City, Ky., to SKW Trostberg A.G. of West Germany.

A second agreement is for sale of Airco's Charleston, S.C., ferroalloys plant to Macalloy Inc., a newly formed company. Macalloy's princi­pal shareholder is Norris B. McFar-lane, who retired from Airco as group vice president in charge of ferroalloys at the end of 1977.

By a third agreement, Airco will sell its Vargon, Sweden, subsidiary, Airco Alloys A.B., to another newly formed company owned by McFarlane.

A backup agreement on the New York and Kentucky plants calls for purchase of these facilities by a newly formed company owned by Satra Corp., a New York City-based inter­national trading firm, should the transaction with SKW fall through. In January, Airco said that it had reached preliminary agreement with Satra for sale of these plants. SKW came on the scene since that time.

Ferroalloys are made from iron and several alloying agents, mainly chro­mium, manganese, and silicon. These alloys are used predominantly by the steel industry to produce stainless, electrical, and carbon steels. The al­loys are also used by foundries to produce iron castings. D

Thatcher: a chemist at No. 10 Downing St. Margaret Thatcher, Britain's new Prime Minister, is both a chemist and a lawyer. The first woman to serve in that post, she faces a welter of na­tional and international problems.

Thatcher, who is 53, isn't the first woman to hold a country's top elec­tive office. Recent history has given us Sri Lanka's Sirima Bandaranaike, India's Indira Gandhi, and Israel's Golda Meir. But Thatcher is certainly the first woman graduate chemist to do so and the first scientist ever to live at 10 Downing St.

Thatcher received a B.A. degree in chemistry from Oxford University in 1946. She then went on to obtain a B.S. degree there in 1949, specializing in x-ray crystallography, and was awarded an M.A. in chemistry the following year.

Airco's ferroalloys faced strong import competition

Thousands of tons

Chromium alloys High carbon (more than 3 %) Lower carbon (3% or less)

Manganese alloys High carbon (more than 4 %) Lower carbon (4% or less) Ferrosilicon manganese

Silicon alloys High silicon (more than 60 %) Lower silicon (60% or less)

TOTAL

1978

181 171

10

585 493

30 62

85 62 23

851

Sources: Commerce Department, Interior Department

U.S. imports of 1977 1976

134 150 110 107 24 43

474 471 370 356 46 61 58 54

76 64 61 50 15 14

684 685

major ferroalloys 1975 1974

198 103 158 71 40 32

341 373 276 290 30 38 35 45

47 93 41 85

6 8

586 569

1973

100 I 70 30

334 265 39 30

63 56

7

497

May 14, 1979C&EN 7