Environmental Technology ChimH409 (2-0-1) Michel Verbanck 2012 Universite Libre de Bruxelles Bruface Dept Water Pollution Control

European Waste Catalogue and Hazardous Waste List (since 2002) classes all wastes into 20 chapters. Examples: Wastes from chemical surface treatment and coating of metals and other materials; non- ferrous hydro-metallurgy Wastes from shaping and physical and mechanical surface treatment of metals and plastics Oil wastes and wastes of liquid fuels Waste organic solvents, refrigerants and propellants Common Industrial Waste Processes: Chromate, Phenol and Cyanide

machine-tool coolants and cutting oils cyanide CN - spent pickling acids Absolutely avoid generate HCN locally !

spent acids (including chromic acid) spent alkaline cleaning solutions cyanide CN - solvents such as phenols Centralized detoxication plant for reception & handling of hazardous wastes

Na 2 Cr 2 O FeSO 4 + 7H 2 SO 4  Cr 2 (SO 4 ) 3 + 3Fe 2 (SO 4 ) 3 + 7H 2 O + Na 2 SO 4 pH < 3 Followed by precipitation at pH close to 9 (see following ‘chevron’ curves characteristic of metal hydroxides solubility) Cr 2 (SO 4 ) 3 + 3Ca(OH) 2  2Cr(OH) 3  + 3CaSO 4 Cr 6+ which is much more toxic than Cr 3+, needs absolutely to be controlled. Chromium is found in wastes from metal plating and finishing operations. It is present in rinse waters from chromic acid baths and in spent baths from electroplating and anodizing processes. The detoxication treatment is by reduction and precipitation, in a process whereby a soluble metallic ion is reduced through an oxidation-reduction reaction and then precipitated by conversion to an insoluble metallic hydroxide. The reaction using ferrous sulfate is Chromate removal

solubility

detoxication of CN - (conversion into cyanates which are less toxic) through electrolytic oxidation Alternatively O 3 can be used as the oxidising agent: CN - + O 3  CNO - + O 2 2 NaCNO (cyanate) + 4 NaOH + 3Cl 2  2CO 2 + 6NaCl + N 2 + 2H 2 O Afterwards, total destruction of the hazardous waste is preferable:

New development: Enhanced oxidation of cyanide by the combined action of hydrogen peroxide and UV irradiation H 2 O 2 itself is also attacked by UV, allowing to produce the highly reactive hydroxyl radical (at the exact location where it is actually needed for the reaction with the waste) Enviolet®-UV-reactor will also eliminate organic chelators (EDTA, NTA...) and other organics if they are present

C 6 H 5 OH + 14O 3  6CO 2 + 3H 2 O + 14O 2 for highest concentrations: recovery in a solvent (typically benzene) followed by phase separation removal of phenols for low concentrations:

Environmental fate and behaviour of LNAPL (Light Non-Aqueous Phase Liquid) and DNAPL (Dense), respectively.

Permeable Reactive Barriers A Permeable Reactive Barrier (PRB) is an engineered emplacement of reactive materials that is placed in the subsurface, designed to intercept a contaminant plume. It provides an obligated flow path through the reactive media, and transforms the contaminant(s) into environmentally acceptable forms to attain remediation concentration goals downgradient of the barrier. Reactive materials widely used (e.g. chlorinated solvents contamination): zero-valent iron, supplemented by a catalyst catalyst (Pd or Ni) underground structure ‘funnel & gate’ configuration groundwater flow

Cement rotary kilns are convenient tools to ensure that the triple T rule (Temperature – Time - Turbulence) is appropriately respected for the destruction of specific organics. These ‘ancillary waste destruction units’ were, for instance, used at the time of the Belgium ‘dioxinated chicken’ crisis in 1999.

Management of fine-grained contaminated sediments deposited in harbours