Color in wastewater may result from the presence of metals, organic acids, microbiological matter, or industrial wastes. Usually, when ProAct treats and removes these contaminants with our water clarification process, the color is also removed. However, this may not always be the case. A notable exception is dye, which may be deliberately added to liquid.
As pipelines are leak- and pressure-tested, dyed water enhances tracking abilities within a system. Similarly, adding color to water bodies allows easy tracking of flow within a given system. Adding coloring agents to fuels is common as well, as color may be used to indicate the quality of a specific fuel.
Many of these agents contain hazardous carbon-based substances with a potential to harm humans and the environment if left untreated. ProAct’s experienced specialists understand that dye removal requires an integration of specified treatment steps.
Although applications differ, the fundamentals of dye removal revolve around the same system parameters: required system flow, the nature and concentration of the additive, and effluent criteria.
System flow targets are typically set by the client. ProAct can usually meet even very high flow requirements. When needed, we have sufficient equipment to run parallel treatment systems, with combined flows that meet client criteria.
Exact chemical compositions of dyes vary between applications, especially between dyes for water and fuel synthesis and transfer. However, they have common characteristics, some of which complicate dye removal. Tracer dyes must be stable; it should not be decomposable by heat, by the traced liquid (be it water or fuel), or by any microbes encountered. It should be visible even in small quantities.
Many tracing dyes have little adverse impact on water chemistry, and many are biodegradable by microbes commonly present in water. However, the presence of color can interrupt photosynthesis and photochemical processes in surface waters. In the absence of strict effluent criteria, water is often treated until turbidity is below 50 ntu, and any color is non-detectable by the human eye.
ProAct has found, through years of experience, that organic compound-targeting adsorbers are often the most effective and economical water clarification method. Adding granular activated carbon (GAC) vessels, or vessels with similar media types removes organic compounds, as these contaminants enter microporous sites available on each grain. With sufficient contact time, GAC is able to adsorb significant amounts of dye.
As the adsorptive media becomes saturated over time, breakthrough of dye occurs. In order to ensure breakthrough does not impact discharge water quality, ProAct typically uses two or more media vessels in series. When breakthrough is observed in the site glass downstream of the first vessel, the second vessel provides ample response time to shut down the discharge and change the media.
Saturated spent non-hazardous media is commonly sent to a reactivation facility, which removes excess contaminants by applying heat. Alternatively, media may be sent to a landfill for disposal.
In order to extend the lifespan and efficacy of adsorber beds, pretreatment steps may be incorporated into a treatment process. Physical filtration removes non-dye particulates which impair water clarity, and which clog adsorbers. Sand filters, bag filters or other filter types frequently precede adsorptive media vessels.
A range of chemical pre-treatment steps may also be sued. Most common in water treatment systems, coagulants and flocculants pair together to remove suspended dyes and other particulates discoloring a given water stream. Similarly, appropriate surfactants make dyes easier to separate from water streams. These surfactants function similarly to detergent in a load of dirty clothes – the hydrophobic ends attach to non-polar contaminants, such as oil, adding weight to and easing the separation of dyes and other like contaminants.
ProAct maintains a fleet of units readily available for adsorption, injection, and enhanced water clarification. ProAct can design and build the most effective system to meet your water treatment needs. ProAct’s experienced technicians can operate your system to maximize the treatment effectiveness. Call a ProAct specialist today.