Useful articles contain excellent information

file:///C:/Users/FT8/Downloads/ijerph-16-02430.pdf

https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0155462&type=printable

Article Evaluation of Recent Treatment Techniques for Removal of Hea...

Francesca, you are interested in bioavailability of metals directly in the wastewater? For example, you are interested in toxicity of metals such as Cu to microbes in the undiluted wastewater, not toxicity of metals to organisms like crustaceans or fish in wastewater after it is diluted into a stream? With >100 mg/L DOC, I presume it is the former.

Even though such DOC concentrations may be far outside the calibration conditions used in the speciation models behind the BLMs such as those of Robert Santore et al or simplified proxies like BioMet, you might find they give you an approximation that might be sufficient for your purpose. For instance, if the models predict very low risk of toxicity, say 1/20 of a toxic unit, you could reasonably assume that risk is low and it might not be worth your time and money to get a better estimate. You would have ignore all the out-of-bound error messages, or maybe enter the closest value that doesn't error out. If it predicts toxicity or close to toxicity, you might need to find someone to conduct bioassays, if getting a more robust answer is important for you wastewater. Those have lots of complications, so not something to dive into without some homework.

There has been quite a bit of work done on at least the speciation and bioavailability of metals in wastewater, although there seems less with actual toxicity. Also wastewater has mixture toxicity and some strange differences from natural waters such as EDTA or other strong chelators. A good read is Sarathy and Allen (2005). It has lots of citing literature that I haven't read that sounds very relevant.

Sarathy, V. and H.E. Allen. 2005. Copper complexation by dissolved organic matter from surface water and wastewater effluent. Ecotoxicology and Environmental Safety. 61(3): 337–344. https://doi.org/10.1016/j.ecoenv.2005.01.006

Hope these thoughts might help. CM

The speciation of metals in different fractions ( dissolved form, particulate form, organically bound form etc ) may be studied.

Thanks to everybody for the answers. In particular, I wanna reply to Christopher A Mebane

We are working with microalgae and we are using undiluted textile wastewater a medium for microalgae growth. In this WW we measured the concentration of different metals and at the same time high concentration of DOC. We started using BLM model and, as you mentioned, now we switched to BioMet. Actually we found a not negligible risk of toxicity, as we obtained values around 1 TU for Copper, and around 0.5 for Zn. The same values were optained for Cr by comparing our concentrations with the EPA quality standards adjusted for water hardness. We are not sure if those values could be reasonably trusted….

"Heavy metal-induced toxicity and carcinogenicity involves many mechanistic aspects, some of which are not clearly elucidated or understood. However, each metal is known to have unique features and physic-chemical properties that confer to its specific toxicological mechanisms of action (Tchounwou, 2012).

The presence of heavy metals in wastewater is reported in the literature. To assess their toxicity, it is first of all necessary to choose the organisms on which the ecotoxicological approach will be applied. Then make the choice between a substance approach or a matrix approach. The results you obtained for Copper and Zinc do not demonstrate the absence of toxicity. They express that the concentration measured for each of these substances, taken in isolation, may have no effect on the exposed organisms. However, it should be remembered that wastewater in itself constitutes a matrix of pollutants, and in this case study the interactions between the metals retained by carrying out an assessment of combined effects or joint toxic effects of heavy metals into wastewaters on the selected organims.

Article Toxic effect of heavy metals on aquatic environment

Article Effects of heavy metals Cd 2+ , Pb 2+ and Zn 2+ on DNA damag...

Article Single and combined effects of nickel (Ni(II)) and cobalt (C...

Article Acute toxicity of organic chemical mixtures to the Fathead minnow

http://en.cnki.com.cn/Article_en/CJFDTotal-NMGX200806020.htm

https://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP23567S.htm

Article Joint-action ecotoxicity of binary mixtures of glutaraldehyd...

Article Individual and combined toxicity of three heavy metals, Cu, ...

Article Acute and chronic effects of water quality criteria‐based me...

Article Assessment of combined toxicity of heavy metals from industr...

Article Fate of glutaraldehyde in hospital wastewater and combined e...

Water plants can be used, such as ducks and azolla, where they reduce the load of organic matter by absorbing it with the necessity of continuous harvesting. thank you

Interesting - Mr Tahseen, what is BLM? ?I am guessing and am likely in the right neighborhood...but thought I would ask.

Reading about plants reminded me of how many times we have identified a "good" that certain plants do...then planted the plant where it never before been - and then we have non-native species knocking out the native ones. My neighborhood has an open area w trees. There are maybe 8 trees and two are native.

I believe similar work was done w tomatoes that absorb metals from the soil - of course, do not put them in your salad.

The toxicity of dissolved heavy elements lies in the drainage water that is treated by physical and chemical methods and when released to water bodies these elements become a cumulative toxic effect within the food chain

thank you

Francesca Marazzi , textile effluent! Oh dear, that is a complex brew. I am based in the USA, and have a bit of a provincial view. Here, risk assessment of effluent toxicity is solely concerned with avoiding (much) harm to fish and invertebrates in the dilute receiving waters (river, bay, lake, and such). I did once work on a risk assessment of a pulp and paper plant that might have some similarities to textile effluent, in that color, organic resins, chlorinated phenols, fibers, and organic acids were identified of concern. It was really too complex for model based risk assessment, and threw up their hands and called for mesocosm and field studies, which in that case decided 0.5% effluent was safe. Unpublished, but there's some gray lit I could come up with.

Here, about the only people who care about potential toxicity of undiluted effluent are wastewater plant operators who need to keep their bioreactors "cooking" properly. They care very much about harm to microbes.

So, yes I could believe that the metals could be toxic in the undiluted effluent, but in a complex brew lots of things could. Even though some metals biotic ligand models (BLMs) sometimes work surprisingly well, in such a brew you might do better just trying to grow out your microbes in beakers. Unfortunately I have no idea what would make a meaningful control! A dilution series maybe? This could give you good information on practical toxicity, but trying to tease out specific chemicals or characteristics causing the toxicity would be very difficult.

Stay safe and good luck!

Chris

Dear esteemed Francesca Marazzi, this is true. I mentioned the dissolved elements that have a toxic effect, especially on the scale of artisanal laboratories that do not depend on the treatment units in the treatment of their water. They contain dyes and their offspring, as well as acids and bases that interact with the organic materials. To get rid of dissolved organic elements such as nitrogen and phosphorous compounds using a duckweed plant, this plant works to represent these compounds in building a living mass and it doubles itself in the event of appropriate conditions and absorbs heavy elements that are considered over time with a cumulative effect affecting neighborhood activities E, including the man who exposed them through the food chain and the quantity of surplus will Tadms on the outer surface of the plant so that water gets rid of the harmful elements of the environment body

Best Regards

Doctor

nidhal tahssen Taha Al-taee