Are you more concern if the electrochemical treatment changes the state of the metals in water or decrease their concentration from waste to treated water?  If so, the process below does not address this issue.  

1. It all depends on the type or separation process you use.  For instance, if there is no reason you should avoid the addition of chlorine you may transform your aluminum/iron into a treatable sludge process (probably after a reasonable dilution of concentrated waste water) since aluminum chloride and ferric chloride may be further isolated...,

2. As far as the concentration in gm/l goes you must know the final and initial volumes of the added chlorine to the portion of treated water and this can be related from the metal concentration of the salts you obtained to the amount of treated water you started with to find the individual metal [ ]'s.  

P.D. May I ask, what is the electrochemical treatment you use from waste to treated water?

Like Caesar I'm unsure what you are trying to estimate.  For example, is it a mass balance?

Sir i am using the Electrocoagulation to treat wastwater (effluent). In electrocoagualtion require metal electrode which goes reduction and oxidation on cathode and anode respectively, pollutants settle down with this anodic material and that is called sludge. there is some residue of metal may dissolve with this treated water. I want to konw how i calculte the amount of residue (meatal) in treated water.

This 2015 resarchgate publication contains all the information you need.

https://www.researchgate.net/profile/Akrama_Mahmoud/publication/281289432_Electro-dewatering_of_wastewater_sludge_An_investigation_of_the_relationship_between_filtrate_flow_rate_and_electric_current/links/57399db708ae9f741b2c6885.pdf

Article Electro-Dewatering of Wastewater Sludge: An Investigation of...