Remove Colour and COD from Tea Wash Water

The Background

Water pollution occurs when harmful substances contaminate waterways, degrading water quality and rendering it toxic to humans or the environment.

The presence of colour in discharge water is often caused by dissolved organics and tannins which are created during the tea manufacturing process. This colouration effects not only the aesthetic appearance of the water, but when this wastewater is discharged to nature, photosynthesis activity becomes limited, which has detrimental effects on aquatic ecosystems.

Moreover, releasing untreated wastewater into the ecosystem can result in:

  • Bioaccumulation of chemicals in the food chain
  • Population decreases in aquatic species


Manufacturers must also adhere to strict limits of Chemical Oxygen Demand (COD) for wastewater which is to be discharged into the environment. Failure to comply with local limitations set for colour and/or Chemical Oxygen Demand* (COD) can result in loss of permit, operational downtime, limited production volume and severe fines, not to mention reputational and environmental damage.

*COD is used as a measure of organic pollutants in water and is expressed in milligrams per litre (mg/L) or parts per million (ppm).

The Project

A tea plantation based in an area of natural beauty, owned by a major beverage manufacturer, approached Arvia to help them to treat their process discharge water. As this tea wash wastewater was going to be discharged to an area of natural beauty, it was a strict requirement to ensure that contaminants were removed and also to eliminate the colouration.

The client’s objectives were to:

  • Achieve the 40 mg/L target discharge consent for COD
  • No visible colour (colouration measured in Platinum Cobalt Units)

By adopting a wastewater treatment process which has the ability to remove trace levels of organics and reduce COD, manufacturers meet regulation and prove commitment to the protection of the environment.

The Solution

Arvia’s Nyex™ 7-100-a system was deployed against this application. This process combines adsorption with electrochemical oxidation in a single, scalable unit. Organic contamination is preferentially adsorbed, localising it onto the surface of the carbon-based Nyex™ media. A low electrical current is then passed through the media bed which fully mineralises the adsorbed contaminants to H₂O, H₂ and CO₂. The electrical current simultaneously regenerates the surface of the media in-situ, allowing for further adsorption and treatment without interruption or incineration.

Results are achieved without chemical dosing or the generation of sludge reducing costs in terms of labour, transport of chemicals and specialist waste disposal.

The Results

The inlet COD was 510 mg/L and following treatment, the water was compliant with the discharge consent, achieving 31 mg/L.

Colouration showed that the treated water was virtually colourless, safe and acceptable for discharge.


Get in touch

To see how the Nyex™ Treatment Systems can be suited to effectively treat your wastewater for the lifetime of your project, get in touch with our industry experts today.

Arvia Technology Ltd

Safer water for future generations


The Heath Business and Technical Park
WA7 4EB (Satnav WA7 4NH)

+44 01928515310
Shanghai office

+86 139 1635 6691