I am trying to remove the color of the pulp and paper industry effluent.
Our WWTP consists of the primary and secondary treatment (activated sludge) systems.
We introduced a new washing system for the bleaching stage (acid effluent). Since then the final effluent color has significantly turned darker (around 1000 mg Pt/L). Additionally, the final effluent chemical oxygen demand - COD has also increased.
What is the explanation for this significant color and COD increase? How can I remove the color of the effluent?
Hydrogen peroxide or Fenton's Reagent should work. If you are interested, please give me a call. I am happy to help. Sean L. Roop, Business Development Manager, USP Technologies - 239-989-3581. We have turn-key systems that would be engineered for your specific application.
If you are using a bleaching agent, it may contain certain amount of chlorine in it as well. Probably due to this the sludge mass has mostly reverted back to anaerobic phase or is dead. Only due to this, the problem of darkening of colour is present. if you can segregate the water stream, and connect it post aeration and pre-filtration, your colour may improve. Only after this step, you may need to check whether the carbon that you have used has a good iodine value. If not, my advice will be to replace it.
The bleach liquore shall be segregated from the main effluent and it should be treated with micro enzymes available in market or else even after bringing the colour down it reappears since this waste contains lignins
The bleach liquore shall be segregated from the main effluent and it should be treated with micro enzymes available in market or else even after bringing the colour down it reappears since this waste contains lignins
Don't know if this is possible (depending on the rate/volume of effluent flow), but could you "polish" the effluent with a carbon (granular activated carbon, GAC- F600) flow through tank?
I have limited knowledge and experience in the area yet felt can help so venturing in with a suggestion.
As far as I understand the colour is because you are using wood, essentially Lignin so why not digest lignin first using an appropriate enzyme.Can suggest and demonstrate a natural source as well. The other problem is the issue of heavy metals in the effluent so even for that can suggest Bioremediation.
I have limited knowledge and experience in the area yet felt can help so venturing in with a suggestion.
As far as I understand the colour is because you are using wood, essetially Lignin o why not digest lignin first using an appropriate enzyme.can suggest and demonstrate a natural source as well. The other problem is the issue of hevy metals in the effluent so even for that can suggest Bioremediation.
The increase of both COD and color after biological treatment is explained by the higher fraction of recalcitrant organics including lignin compounds (brownish color) after changing the washing in the bleaching stage.
Because traditional activated sludge systems including MBR, remove mainly readily biodegradable soluble organics (“fast” food), we upgrade this to capture and biodegrade the “slow” food and recalcitrant organics including color as well without using any chemicals. In 2009 we applied this in a large pulp & paper wastewater treatment resulting in very low COD and color (80% - 90% removal).
If interested, I would be happy to send you more information via email.
Anaerobic digestion in first stage if systems suits your country's climate.
Followed by Electro-Cogualation --> filtration with mechanical press filters --> Ozone diffussion to settle balance COD / BOD and need be little chlorine (only if required) periodically.
In case anareobic digestion is not working for all seasons then Primary Filtration with 3 Micron press filter followed by Electro-Coagulation followed by Press Filter again and then Electro-Oxidation
Solutions to all complex problems need not be Complex always!
Physicochemical methods like coagulation with lime or iron salts, ultrafiltration etc. have not been very effective for color removal of pulp & paper mills effluents. Adsorption of activated carbon is a common method for color removal of industrial effluent but the high cost is a limitation for its use for pulp & paper mills. Therefore attempt has been to find out low-cost adsorbent material for removing color of effluents of the industries. Coal fly ash of power plants has been used as an adsorbent for removing metals like Hg,Pb,Cd, Zn and Fe from water (De, 2005; De & Lal, 1990).But use of coal fly ash for color removal of Pulp and paper effluents has not been reported. In the present investigation , coal fly ash has been used for the color removal of pulp and paper mill effluents. Coal fly ash is an efficient adsorbent in removing color of pulp and paper mill effluents.100% color removal was achieved at pH 6.8 and above.
Effect of pH
Effect of pH Effect. of pH on color removal of the paper mill effluent was studied using 0.5 M NaOH or 0.5 M HCl (Fig. 2). 100% color removal took place at pH 6.8 and above. This result is significant as normal pH of paper mill effluents are above 8.0, the method may be used for color removal of pulp and paper mill effluents without any pH adjustment.
Colour removal by active and gamma sterilized compost
Color removal experiments using active and gamma sterilized compost showed that the color removal capacity for both wastewaters was nine times higher when using active compost than for those reactors using gamma sterilized compost. Final decolorization for pulp mill upset tank and E stage filtrate was 91 and 83%, respectively, while only 33% decolorization was achieved with gamma sterilized compost. Kinetic tests also showed higher color degradation rates when using active compost compared to sterilized compost. Additional experiments demonstrated that biological color removal appears to be robust with respect to pH and is largely unaffected by pH over a range from pH 5 to 10, typical values for the effluents in paper mills. The effect of aging in sorption were tested and results showed that virgin compost could establish a microbial population in less than 50 days which resulted in a compost with sorption capacity similar to the aged compost.
Colour removal by Membrane
Membrane technology has become widely accepted in many seawater and brackish water treatment applications and these days it is more often used also in variety of waste water treatment processes as the final treatment step of water re-use process. In addition to traditional use of membranes for desalination, new requirements have been challenging membrane manufacturers to develop special products for selective removal of hardness, natural organic matter, color, fats, proteins and other macromolecular species. Nanofiltration (NF) membranes are usually used for selective removal of certain species in applications when TDS reduction is not a priority.
Colour removal Coagulation Process
The pulp and paper mill effluent is one of the high polluting effluents amongst the effluents obtained from polluting industries. All the available methods for treatment of pulp and paper
As you know, in any wastewater treatment application the bulk of the work has to be done by bio filtration.
If you have considerable colour problem, you should probably see if you could optimize or improve your bio filtration system.
If you like I will gladly give you some good ideas how to improve efficiency of your bio filtration and aeration.
The better and the more effective is your bio filtration the less expensive will be the polishing and colour removal system, using oxidizers as ozone and the whole project will be more economical.
Mechanical micro filtration is typically way too expensive as far as energy consumption is concern to be used in wastewater treatments.
Sorry for the late reply. First of all, thanks for your comments on this subject. As you propose, I woul be interested in hearing your ideas on how to improve efficiency of your bio filtration and aeration.
Ozone generators which are typically used in pulp and paper industry are producing ozone in kilograms and even tons per hour, using ozone generators similar in size to an elephant. They typically are treating millions of litters of water. Do you produce such equipment or are you familiar with this size of ozone applications?
I am afraid that your opinion is based on incorrect ozone implementation and most likely poor quality and technologically inferior equipment. Unfortunately over 95% of ozone applications are done by people ignorant of ozone technology and that make results of the implementation ineffective, inefficient and expensive giving ozone stigma and bad name.
My opinion is based on thousands of ozone system installations done all over the world and calculations.
When I have done comparative calculations in the past with many oxidizing technologies vs ozone and they we considerably more expensive. If you are interested please bring forward an example of a technology that you consider comparable in price and we will see which one is more economical right here in the descussion.
Here in paper country we use oZone for odor and color removal. I would go with Misha's recommendation. Opex and capex are comperable to alternative technologies
Hi Carlos, I am a supplier of aqueous ozone from clean core technology, 3gpm or more if needed. On demand when all that is needed is cold water electrical outlet, our unit only uses 2.5 cents per hour of electricity, If ozone is what you want contact me.