Concrete Washwater

Harmful Ingredients

Concrete or cementitious (mortar, grout, plaster, stucco, cement, slurry) washout wastewater is caustic and considered to be corrosive with a pH over 12, essentially the same as Liquid Drano®, Ammonia or other household cleaning detergents. The primary ingredient in ready mixed concrete is Portland Cement, which consists of Portland Cement Clinker, Calcium Sulfate, Calcium and Magnesium Oxide, heavy metals and potassium and sodium sulfate compounds, chromium compounds and nickel compounds. Some of the contaminants contained within concrete washwater include; Aluminum, Barium, Chromium, Hexavalent Chromium (Chromium 6), Copper, Iron, Magnesium, Manganese, Nickel, Potassium, Selenium, Sodium, Vanadium, and Zinc. The washwater may also contain trace elements of petroleum products, admixtures and other materials from processing or treating the material. The graph to the left outlines the contaminants and their respective levels.

Contact with wet (unhardened) concrete, mortar, cement or other cementitious materials can cause skin irritation and severe chemical burns or serious eye damage.

What is pH?

pH is a measure of how acidic or alkaline a substance is. The pH scale goes from 0 to 14, where 7 is neutral. A low pH value means the sample is acidic, while a high pH value means that the sample is basic or alkaline. A change in one pH unit means a tenfold change in concentration, similar to the Richter scale and measuring earthquakes.


Effects of High pH on Aquatic Life

The effects of high pH on fish may include: DEATH; damage to outer surfaces like gills, eyes, and skin; and an inability to dispose of metabolic wastes. High pH may also increase the toxicity of other substances. For example, the toxicity of ammonia is ten times more severe at a pH of 8 than it is at pH 7. The safe range for aquatic life is between 6.5 – 9.0 pH units. The average pH of concrete washout water is near 12 pH units.

Effects of High pH on Vegetation

The effects of high pH on vegetation may include: inhibited growth, damage to soil and plants and substantial alteration of the soil and plant chemical composition even after the pollution source is gone. High pH may also increase the toxicity of other substances causing further problems. The safe range for plant life is between 6.5 – 7.0 pH units. The average pH of concrete washout water is near 12 pH units.

High Suspended and Dissolved Solids Count

Concrete wash water is basically slurry of fine Portland Cement particles in water, also called suspended solids when in water. When illegally discharged into a fish-bearing waterway, it will clog fish gills; reducing the amount of oxygen they receive which can ultimately lead to death. It can also smother aquatic habitat, impair their feeding ability and permanently damage the fragile ecosystem we enjoy. Turbidity, which refers to water clarity, is related to suspended solids. In clear water, the turbidity is 0 NTU and fish are able to capture their prey, however as the turbidity increases to 60 NTU, certain fish are only able to capture 5% of their prey. The average turbidity of concrete washout water coming directly from the source is 27,000 NTU. The average stream or river in the United States has a total suspended solid count of no more than 75 ppm. The average total of suspended solids in concrete washout water coming directly from the source is 79,000 ppm.

Impaired Waterways Impact Us All

40% of the waterways in the United States are still impared; unable to swim, fish, play or otherwise use the waterway and 70% of those because of non-point source pollution (ie., concrete washout water). As construction in the United States and worldwide continues to boom, we are faced with a pollution problem of epidemic proportions. The building and concrete industries need to continue to combat this problem quickly, effectively and need to be armed with the most innovative and state of the art equipment and procedures available; Concrete Washout Systems portable and patented roll-off bin.

What is CWS Doing About It?

CWS is the ultimate risk management and compliance system for concrete washout containment. Not only do we have a product that controls, captures and contains all of the concrete and washwater material, we employ a system and method in which we divert and recycle the concrete material and recycle all of the caustic concrete washwater that was generated on a jobsite. CWS has also developed a patent pending treatment and recycling system that reduces the contaminant levels in concrete washwater so it may be used for other applications and/or recycled.