Arsenic

Arsenic’s evil reputation is manifested in its old alchemy symbol: a coiled serpent ready to strike. Considering arsenic’s eminence as the preferred homicidal agent of detective novels, it is not surprising there is a great deal of anxiety over its possible presence in water, among other substances, we use on a daily basis.

I am an evil, poisonous smoke… But when from poison I am freed Through art and sleight of hand,
Then can I cure both man and beast From dire disease oft times direct them;
But prepare me correctly, and take great care That you faithfully keep watch over me; For else I am poison, and poison remain
That pierces the heart of many a one
– Valentini 1694

HEALTH EFFECTS

At low doses, arsenic may be beneficial to human health, but there is no conclusive evidence that it is essential. Acute, high-dose oral exposure typically causes gastrointestinal irritation, extreme thirst, low blood pressure, convulsions, and can result in death from cardiovascular collapse; the estimated lethal dose for adults is 70–180 mg. While high-dose exposure is rare, long-term exposure to 10–100 µg/kg/day often leads to neurological, skin, or liver toxicity, but exposures below 1 µg/kg/day have not shown detectable effects. Chronic exposure increases the risk of several cancers: inhalation raises lung cancer risk, while ingestion is linked to skin and internal cancers

REGULATORY BACKGROUND

The USEPA published the Final Arsenic Rule in January 2001, that set the maximum contaminant level to 10 µg/L ( 0.010 mg/L).

THE PUREFLOW SOLUTION

The Pureflow system for arsenic filtration is an improved design for the water treatment industry. A highly adsorptive, NSF approved, media and chemical pretreatment system combine to provide a simple, safe, compact filtration system requiring minimal attendance by maintenance personnel.

The removal of arsenic occurs by its adsorption onto an iron precipitate that is formed in the Pureflow pretreatment process. The Pureflow multi-media filter includes a highly adsorptive active media that adsorbs the iron and arsenic in, essentially, oxidized forms. The Filter media is cleaned by back washing the filter with processed water. The backwash to filtration ratio is less than 5%.

Well water containing arsenic is chemically treated with an oxidant (such as chlorine) at the first static mixer. If dissolved iron (in sufficient concentration) is not present in the raw water, ferric salt is also fed ahead of the second static mixer. The iron is oxidized to a processable form, and a free chlorine residual is provided to the water distribution system.

The filter media does not contain greensand or activated alumina, and, therefore, does not require costly regenerating chemicals such as potassium permanganate or acid / caustic solutions. Backwash water is usually discharged to the sewer system. An optional backwash water reclaim system is available to reclaim approximately 99% of the backwash water.

The chemical pretreatment is manually set and automatically operated. The filter effluent is continuously monitored with a chlorine residual analyzer to permit the positive, simple, and automatic adjustment of the chemical feed pump.

A field pilot testing program is available to ensure the proper design and operation of every system. The cost of this program is deductible from the purchase price.

Permanent and disposable media systems
ASME code pressure vessels up to 250 psi
Oxidation pretreatment equipment
Multi-media filter load (NSF 61 Approved) Filter face piping
Electrically operated butter0y valves Filter flow control valves
Backwash flow control valves
Automatic control panel (PLC Based)