In　order　to　understand　if　a　conventional　wastewater　treatment　progress　can　provide　sufficient　protective　screen　of　heavy　metals,　a　long　term　monitoring　was　conducted　for　the　influent,　effluent,　and　water　at　different　stages　of　a　domestic　wastewater　treatment　plant.　As　a　result,　eight　heavy　metals　such　as　As,　Cd,　Cr6+,　Cu,　Hg,　Mn,　Pb,　Zn　were　detected.　For　most　of　the　heavy　metals　about　40%　removal　could　be　obtained　by　the　secondary　treatment　progress.　Of　the　total　removal,　10　to　20%　was　achieved　by　the　primary　settling,　while　20　to　40%　was　achieved　by　the　following　biological　units.　Through　a　series　of　adsorption　experiments　using　quartz　sand,　kaolin　of　known　size　distribution　as　inorganic　adsorbents　and　laboratory-cultured　activated　sludge　as　organic　adsorbent　for　adsorbing　model　of　the　eight　heavy　metals,　it　was　found　that　the　adsorption　of　heavy　metals　by　the　inorganic　adsorbents　well　followed　by　the　Langmuir　isotherm　with　the　saturation　capacity　proportional　to　the　specific　surface　area　of　the　solid　particles,　indicating　a　single-layer　adsorption　property.　However　for　the　activated　sludge,　its　adsorption　isotherm　showed　a　property　of　multilayer　adsorption　and　the　adsorption　capacity　was　one　order　higher　than　the　inorganic　particles.　The　different　behavior　of　the　activated　sludge　from　the　organic　particles　for　model　heavy　metals　adsorption　explained　the　mechanism　of　heavy　metals　decay　in　the　different　stages　of　the　conventional　wastewater　treatment　plant　and　indicated　that　the　activated　sludge　in　the　biological　treatment　plant　unit　played　the　main　role　for　heavy　metals　adsorption.　©　2014,　Journal　of　Chemical　and　Pharmaceutical　Research.　All　rights　reserved.