Table 2: Comparison among wastewater treatment technologies.


Chemical precipitation(i) Simplicity
(ii) Inexpensive capital cost
(iii) Adapted to treat high heavy metal ions concentration
(i) Ineffective when metal ion concentration is low
(ii) Not economical
(iii) Produce large amount of sludge

Ion-exchange(i) Widely applied for heavy metal removal
(ii) Ion-exchange resins can be regenerated
(i) Secondary pollution can be caused due to regeneration by chemical reagents
(ii) Expensive when treating a large amount of wastewater so cannot be used at large scale

Membrane filtrationHigh heavy metal ions removal efficiency(i) High cost and complex process.
(ii) Membrane fouling has limited heavy metal removal

Coagulation-flocculationGood sludge settling and dewatering characteristics(i) It involves chemical consumption
(ii) Increased sludge volume generation

Flotation(i) High metal selectivity
(ii) High removal efficiency
(iii) High overflow rates
(iv) Low detention periods
(i) High initial capital cost
(ii) High maintenance and operation costs.

Electrochemical(i) Regarded as rapid and well controlled which requires fewer chemicals
(ii) Provide good reduction yields and produce less sludge
(i) Involving high initial capital investment
(ii) Expensive electricity supply

Adsorption(i) The high cost of AC limits its use in adsorption
(ii) Many varieties of low-cost adsorbents have been developed and tested to remove heavy metal ions
(iii) Biosorption is a relatively new process that has proven very promising for the removal of heavy metal from wastewater
(i) Removal of heavy metals from low wastewater concentration
(ii) Adsorption efficiency depends on the type of adsorbents