Emissions of pollutants

There are many chemicals involved in the textile manufacturing process, such as biocides, surfactants, reducing agents, stain removers, various types of acids, waxes, fats, salts, binders, thickeners, etc., and there are many steps. But all elements have one thing in common, they all add their part of harmful pollutants to the wastewater. From dyeing, bleaching, gluing, heat welding, softening, blasting and wetting, to the various coloring the yarn or the fabric, printing, all the way to the finishing process, all phases produce high concentrations of biologically difficult-to-degrade compounds.

One of the major sources of emissions of pollutants originates from the fabric printing process where a decorative design or text is applied to fabric products by various screen printing methods. This process leads both to recalcitrant molecules in the production wastewater and as Volatile Organic Content (VOC) gas. Surging environmental restrictions require effective treatment of these air and water streams in order to secure a healthy work environment and avoid polluted water recipients. In many facilities, jeans and other clothes are commonly bleached to create a “washed” look.

All of the challenges in the textile industry mentioned above can be achieved with ozone treatment, which presents a very effective way of reducing operational costs and lower environmental emissions compared to traditional techniques.

Color removal from textile wastewater

The release of colored wastewater from the textile production represents a serious global environmental problem and a real public health concern. Color removal from textile wastewater is a huge challenge for the industry. Up to now, there hasn’t been a single nor a combination treatment technology available on the market, that effectively could decolorize the effluent wastewater, which also has been economically attractive and would help meet the environmental goals of the production facility.

Water scarcity

Water scarcity has become a major issue all over the world, especially in the region where textile production occurs. With a growing demand for water resources, traditional methods for process and wastewater treatment in the textile industry must be replaced by more sustainable methods such as the technology that Mellifiq offers, in order to have a sufficiently high quality of the process and the effluent wastewater.

Stringent environmental standards

The increasingly stringent environmental standards and legislations that are being introduced by more and more countries in response to, among other things, the textile industry’s increased water consumption, is also an important challenge for process water and wastewater treatment in the industry.

Typical pollutant load from the textile industry

The solvent used to produce printing paste will be wasted during the drying or printing process, generating VOC and wastewater containing organics which are difficult to treat. On average, screen printing runs may require up to 1,200 kg of organic solvents, most of which are emitted as VOC from the dryer process. Up to 80 kg of organic solvents can be emitted in the wastewater. The US EPA has estimated the following potential emissions in various forms from textile printing, based on information directly from the textile industry. Similar printing processes exist in the carpet textile industry.

Emission constituents

Both VOC and aqueous waste from the printing process contain various organics such as alcohols, dyes and aromatics. The table below displays common emission constituents in the wastewater and VOC.

Mellifiq’s ozone treatment for screen printing emissions

Wastewater

Mellifiq have more than 20 years of experience in using advanced oxidation technologies like ozone technology. Ozone technology is a proven effective method to treat the compounds both in the wastewater and the VOC by effective oxidation of organic molecules. Wastewater typically contains high levels of COD with a COD:BOD ratio of 4:1 to 5:1.

Not only does ozone oxidize the organic pollutants, it is capable of converting non-biodegradable COD to readily biodegradable BOD, lowering the COD:BOD ratio for subsequent biological treatment. Depending on the COD and BOD concentration, ozone can oxidize the majority of the compounds which lowers the wastewater load to acceptable regulatory levels. An ozone system for textile wastewater may save significant operational costs and footprint.

Mellifiq has successfully treated screen printing wastewater from a large international clothing supplier, reducing COD levels from 700 mg/L to 100 mg/L and BOD levels from 150 mg/L to 50 mg/L using our compact systems. The full scale system is treating 20 m3/hr of organic wastewater per day to comply with local regulations.

We welcome you to read more about how we treat BOD and COD with ozone-based treatment systems. Read more about this here!

Compared to typical treatment by incineration of hazardous volatile compunds, ozone effectively reacts with these pollutants in gas phase. This eliminates the major energy demands that follows incineration. For VOC gases, ozone is typically combined with an active carbon filter where ozone treatment reduces VOC gases up to 90% with secondary polishing to reduce completely the fugitive gases. Please visit the VOC treatment application page to read more.

Textile bleaching by ozone

In modern designer clothing production, fabrics such as jeans are bleached using oxidation by chemicals to create a washed look. The highly oxidative characteristics of ozone enable a sustainable bleaching method without excessive chemical handling or costs. In addition, ozone leaves no by-products which need to be treated. Please go to our Bleaching application page for more information.

Ozone color removal

Textile wastewater is often treated on-site using biological wastewater treatment processes. This may provide around a 90% reduction of the incoming COD and BOD. The remaining COD and BOD may still constitute major environmental loads. Typically it is not possible to remove the discoloration of the wastewater originating from the textile production described above. Ozone is a very effective color removal technology as a part of the tertiary treatment step. Complete color removal can be achieved in 5-15 minutes of ozone exposure depending on ozone capacity. At the same time, COD and BOD can be treated to achieve near-zero emissions from any textile factory using ozone.

The Ozonetech RENA system powered by the superior corona discharge technique

For ozone treatment at textile factory, Mellifiq employs the Ozonetech RENA Tellus X series, which is Mellifiq’s tailored solution for large loads. Click here to read more about this system.

At Mellifiq, we base each treatment solution on tailored design and engineering, combining ozone with suitable pre-treatment and polishing steps. Depending on the requirements, we design our systems with up to 100% removal of both recalcitrant molecules in the production wastewater and as Volatile Organic Content (VOC) gas.

All RENA systems are designed with utmost attention to detail and performance, specifically low energy consumption and low maintenance need.

Pharmaceutical residues are typically present at nanogram and microgram levels depending on the source. Our most common designs cover ozone treatment, which degrade micropollutants at a very high rate, followed by carbon filter polishing, or extended ozonation. Our designs allow for treatment costs of less than €0.0065/m3.

In-house designed final polishing

All water treatment solutions combining a RENA system and a final polishing step are sized and configured for each specific client and task. With the introduction of O-GAC™, the time and cost of replacing the activated carbon are highly reduced.

Ozone and activated carbon – a perfect match

Granular Activated Carbon (GAC) units are good alternatives to oxidation based API removal systems, although frequent maintenance must be considered. We have developed a unique combined oxidation-GAC system that significantly reduces the GAC replacement and backwashing requirements. Each GAC unit is in-house designed to achieve the most optimal combination with regard to power consumption, removal rate and footprint.