US EPA has established a two-step process to determine enhanced coagulation requirement for TOC removal where it depends on water TOC concentration and alkalinity. Referring that the minimum TOC removal percentage that coagulation has to meet is 30%.
Dear Mehmaz,
It is just about 40% the typical DOC removal at the drinking treatment plant of my city (Burgos, Spain), using conventional coagulation-flocculation. The raw water (coming from a reservoir) has a low DOC concentration (about 2.7 mg C/L) and also a low mineralization, alkalinity and calcium hardness.
Best regards from Spain,
Francisco
It depends on your intention (what you intend to do) with your treated effluent. Can you be more specific about that?
the aim is to reduce the concentration of DOC as THMs precursors. The source water used in this study has elevated level of DOC (16 mg/L) and alkalinity (330 mg/L CaCO3). the point is coagulation is the first step of the treatment and there are some treatments such as activated carbon and sand filter located down stream which can result in further DOC removal.
It seems the primary purpose of the coagulation in this case is pre-treatment for the sand and carbon filter and not directly preparing the water for chlorination as I suspect is the goal in the EPA guideline. Therefore, considering the high nominal DOC, it seems reasonable with the 40% removal.
There are guidelines for British Columbia Mehrnaz; link attached.
http://www.env.gov.bc.ca/wat/wq/BCguidelines/orgcarbon/ocarbon_over.html
Dear Mehrnaz,
I am not sure that a discussion about a percentage (40%) is the solution here. Generally the natural waters used for drinking water treatment is 10 times lower. Inthis cas, a pre-treatement of the waters with chlorine dioxide (or ozone) will lower the THM formation. So even if you have the so called 40%, the THM production will be lower at the end of your process.
Hi,
Gentleman
To reduce DOC on raw lake water is a tough challenge. NOM can be comprised of different size, charge and hydrophilic characteristics. The situation is more complex on stratified, eutrophic lakes. However, we have experienced good results by applying two complementary technologies.
Firstly is a lake restoration technique that mixes / oxygenates all the water column at the same time ammonia, sulfur gases are eliminated together with reduced metals like Mn and iron. This makes the water coming to the plant more homogeneous ,even during high rain or draught season.
https://www.youtube.com/watch?v=_hy13fUIaMw (Spanish)
Secondly a technology that allows to concentrate the coagulant agent up to 1,000 ppm has shown to reject the most reactive portion of the DOC. The concentration of the coagulant is achievable since the solids are moved through a ceramic membrane 0.1 µ using the cross flow mode.
https://www.youtube.com/watch?v=1Eh_IQbBWDM
There are several manufacturers that may have option for the first technology, not sure if there are more besides the one we have validated for the second one.
Let me know if more information is needed
The degree of removal will depend on the hydrophobicity of the organic matter in the water and this turn is dependant on source, type, average molecular weight etc. In my opinion, a thorough understanding of the organic matter in a specific water will be required to determine what level of removal can be expected through normal treatment technologies. Additional treatment might be required to achieve a predefined removal level.
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