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Ask-Guru-thread-21


Keywords :- Remediation of sites contaminated with CCA - Copper Chrome Arsenate (wood preservatives) and coal tars from old coal gas works.

Enquirer, Request, 1st response, 2nd response, 3rd response,
4th response

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Enquirer


From: Alan Lee
Date: 19th May 1998
Subject: Sites contaminated with Copper Chrome Arsenate, and Coal Tars

 

Request


I am looking for information about the remediation of sites contaminated with CCA (Copper Chrome Arsenate - wood preservatives) and coal tars from old coal gas works.

Regards

Alan Lee

 

1st response

 

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From Dr Hackenbush

Hidden in the depths of the ContaminatedLAND website, are details of DoE Industry Profiles - covering both of these subjects.

  1. Gasworks, coke works and other coal carbonisation plants (ISBN 1 85l 122 32 X) 10

  2. Timber treatment works (ISBN 1 851 122 834) 10

 

2nd response

 

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From Michael J Brooks

The problems caused by Arsenic contamination from CCA (Copper Chrome Arsenate) fade into insignificance when compared to arsenic contamination of drinking water in the Third World.

(Sunday Telegraph 5th April 1998 - Bangladesh irrigation wells sunk into bedrock with raised levels of naturally occuring arsenic, put millions at risk)

Arsenic in drinking water is a known public health danger and poses a significant cancer risk. In the US the Safe Drinking Water Act Amendments of 1996 require the EPA to propose a revised standard by 1st Jan 2000.

The existing US standard of 50 ppb for arsenic in public water supplies, will be revised by 1st Jan 2000 (possibly to within the 2 to 5 ppb).

The new WHO limit has been revised down to 10 ppb. This will be the new EC limit from 2003.

In surface waters the most common ionic valance state of arsenic is As (V) or arsenate. As (III) or arsenite, the most toxic form, is more likely to occur in anaerobic ground waters (well water). In the pH range of 4 to 10, the predominant As (III) compound is neutral in charge, while the As (V) species are negatively charged. Most removal technologies are based on chemical charge; therefore removal efficiencies for As (III) are poor compared to removal of As (V).

The Current Best Available Technologies in the US for arsenic removal are most effective in treating As (V). As (III) can be converted to As (V) using chlorine, potassium permanganate, hydrogen peroxide and ozone.

  1. Coagulation/Filtration (CF)
    The traditional process for removal of particulate and As (V). The major drawback is the disposal of by-product sludge.

  2. Lime Softening (LS)
    Problem of disposal by-product sludge, however secondary treatment is required to meet 2 ppb std.

  3. Activated Alumina (AA)
    Most effective at removing As (V) at a pH of 6. Highly concentrated hazardous waste by-streams produced during regeneration.

  4. Ion Exchange (IX)
    Uneconomic for sulphate levels above 200 ppm. Highly concentrated hazardous waste by-product stream.

  5. Membrane Filtration (MF); Reverse Osmosis (RO) and Nanofiltration (NF) and Ultrafiltration (UF)
    Stainless steel and PVC materials may be required for corrosion resistance. 20-25% water rejection, large volumes of arsenic contaminated reject water are a possible disposal issue.

  6. Lanthanum Oxide/Silica (LaSi)
    Selectively adsorbs both As (III) and As(V). LaSi is a new product, needs pilot testing to confirm capital and operating costs. Highly concentrated, low volume waste streams are produced requiring sophisticated process control and safe arsenic residue disposal.

Michael J Brooks
EnviroMet Consultants


3rd response

 

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From: Mohammed Ahmadul Hoque
Organisation: Surface Water Modelling Centre, Bangladesh
Date: 22nd Nov 1998

Regarding your request for information on Arsenic contamination from tube-wells in Bangladesh, I am told that our report will be published by the mid of the next month. We hope then we'll be able to give you more information on the subject.

Mohammed Ahmadul Hoque
Surface Water Modelling Centre, Bangladesh


4th response

 

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From: Micky Allen
Date: 10th May 1999

ENN Daily News (5th May 1999) had an article about two researchers from the Center for Environmental Studies at Stevens Institute of Technology in Hoboken, New Jersey, who have come up with a low-cost, easy-to-implement method of removing arsenic from water that could serve an immediate need in Bangladesh.

The process uses direct coprecipitation and iron-oxide based coagulants. It involves adding inexpensive and readily-available chemicals to well water, mixing it up and then straining the water through a sand filter. The process has been able to reduce arsenic levels in water from 600 micrograms per litre to less than 50 micrograms per litre. The process is quite standard in terms of water treatment but has an enhanced value -- the use of simple products that are readily available to the Bangladesh citizens including two-litre cabonated drink bottles.

It is believed that 30 million people in Bangladesh are affected by naturally occurring arsenic contamination in their drinking water. About 1.2 million of those people are severely affected. Water wells in 59 of Bangladesh's 64 districts are contaminated, according to Dainichi Consultant Inc. of Gifu, Japan.


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