This wastewater should be like municipal or simulating a specific industry?

Dear Henrik, For instance to prepare Synthetic waste water containing Cr2+, analytical grade substance like Cr2O3 are dissolved in distilled water. Hear my question is the procedural activities to dissolve the analytical grade substances in distilled water (How much amount of Cr2O3 is dissolved in ??? amount of distilled water. Then what is the concentration of Cr in this synthetic wastewater?) Thank you!

This wastewater should be like municipal or simulating a specific industry

Are you thinking on any specific type of wastewater?

Organic matter content changes from urban to industrial wastewater. Industrial wastewater can have syntethic complexing compounds or acidic pH that change metal speciation.

Synthetic wastewater is prepared by dissolving salts of the metals intended to be in the wastewater. Their concentrations are calculated as one would do when preparing a solution of known concentration, mg/L. A composite solution is made by mixing these metal salts in one solution. This poses a challenge of some metals precipitating, so one needs to have the knowledge on how the metals interact. One might first determine the concentrations of different metals present in real wastewater to have idea of the concentrations to work with in synthetic wastewater.

And what is this wastewater for?

Are you evaluating analytical methods? Or some wastewater treatment?

Good discussion

Thanks for the clarification Yohanis Birhanu.

A practical method for preparing metals spiked wastewater that is used in all the laboratories I worked in, is to prepare a stock solution of the metal salts in pure water acidified to e.g. pH 2 with nitric acid. This keeps metals in solution as metals are generally soluble in low pH and nitrate is not forming insoluble salts.

The stock solution is made with reasonable amount of the analytical standards as to fit with the precision of the balance. Typically weigh out more than 100 mg portions and dilute into a volumetric bottle.

The artificial wastewater is then prepared by transferring the calculated volumes of stock solution into a contained with the absolute volume of the desired amount of wastewater. Fill water to e.g. 90%. Add the other components of the wastewater receipt and fill to the mark.

One need to calculate the solubility of the metals in the final solution considering all components e.g. phosphate.

The easiest is to dissolve an adequate amount of Cr, As or Cd salt in the tap water. In this way you obtain a solution with known concentration of heavy metal ions, together with the others constituents of water.

Dear Iñigo Legórburu, it is to evaluate analytical methods.

Dear Yohanis,

If you are preparing synthetic wastewater I suggest you:

-For industrial wastewater: Eckenfelder et al., 2009 // Degremont's Manual (Suez Environment) // US-EPA has a lot of information. Look for effluents guidelines and treatment technology databases.

-For urban wastewater there are several recipes for high, medium and low strength. A literatura survey can give you some results that you can apply in your work. A basic recipe is: 20g/l of sugar // 3 g/l of nitrate (Na or K) // 1 g/l of phosphate // 0,5 g/l os manganese sulphate. Add some vegetal fat (3 g/l) to slow the overall process and a pigment (Chlorophyle, Methylene blue...) can be used for the following of the degradation. There are more complex recipes: Look for a Report from Florida University (Contract LPC65). They used a mixture of dextrose, dog food, Spam and Crisco...

As a last step I would perform some test with spiked real wastewater...

Industrial wastewater.

It is worth noting that the term "wastewater" is typically used to describe real samples- not synthetic ones.

Follow

Refer to the valuable book of "Standard methods for the examination of water and wastewater", which in all the requirements including preparing, maintenance (i.e. type of the container, temperature, persistence requirements, etc.), measurement, the effect of interferes, and so on has been detailed.

Interesting discussion

You guys do not talk about biological treatment, why?

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Dear Yohanis Birhanu

Generally, salt of these metals like K2Cr2O7 for Cr(VI) used to dissolve into the appropriate amount of distilled water (with proper calculation of concentration of concern metal). Some studies also include NaN3 to avoid microbial contamination. However, I feel if one really wish to simulate waste water then it must be prepared in tapwater which should be prior analyzed for its ionic strength and other properties like pH, BOD, TDS etc.