A method for treating wastewater containing dissolved metals, the method comprising: treating the wastewater in a primary treatment sub-system and a secondary treatment sub-system in fluid communication with and downstream of the primary treatment sub-system, removing biological contaminants from the wastewater in the second treatment sub-system to produce a partially treated wastewater having a reduced concentration of organic contaminants as compared to the wastewater and including a dissolved metal; introducing the partially treated wastewater into a reactor tank of a tertiary treatment sub-system in fluid communication with and downstream of the second treatment sub-system together with a ballast material and a coagulant to form a ballasted effluent including ballasted solids; adjusting a pH of the partially treated wastewater in the reactor tank to achieve a pH in the reactor tank at which a compound including the dissolved metal is substantially insoluble; introducing the ballasted effluent into a solids-liquid separator , and separating the ballasted effluent into ballasted solids and a solids-lean effluent in the solids-liquid separator and operating a controller to recycle a portion of the ballasted solids from the solids-liquid separator to the reactor tank through a recycle conduit in an amount sufficient to generate an amount of metal hydroxide floc in the reactor tank sufficient to reduce a concentration of dissolved metal in the reactor tank to below about 10 micrograms/liter; characterised in further, comprising recycling between 5% and 25% of ballasted solids separated from the ballasted effluent in the solids-liquid separator to the reactor tank . treating the wastewater in a primary treatment sub-system and a secondary treatment sub-system in fluid communication with and downstream of the primary treatment sub-system, removing biological contaminants from the wastewater in the second treatment sub-system to produce a partially treated wastewater having a reduced concentration of organic contaminants as compared to the wastewater and including a dissolved metal; introducing the partially treated wastewater into a reactor tank of a tertiary treatment sub-system in fluid communication with and downstream of the second treatment sub-system together with a ballast material and a coagulant to form a ballasted effluent including ballasted solids; adjusting a pH of the partially treated wastewater in the reactor tank to achieve a pH in the reactor tank at which a compound including the dissolved metal is substantially insoluble; introducing the ballasted effluent into a solids-liquid separator , and separating the ballasted effluent into ballasted solids and a solids-lean effluent in the solids-liquid separator and introducing the partially treated wastewater into a reactor tank of a tertiary treatment sub-system in fluid communication with and downstream of the second treatment sub-system together with a ballast material and a coagulant to form a ballasted effluent including ballasted solids; adjusting a pH of the partially treated wastewater in the reactor tank to achieve a pH in the reactor tank at which a compound including the dissolved metal is substantially insoluble; introducing the ballasted effluent into a solids-liquid separator , and separating the ballasted effluent into ballasted solids and a solids-lean effluent in the solids-liquid separator and operating a controller to recycle a portion of the ballasted solids from the solids-liquid separator to the reactor tank through a recycle conduit in an amount sufficient to generate an amount of metal hydroxide floc in the reactor tank sufficient to reduce a concentration of dissolved metal in the reactor tank to below about 10 micrograms/liter; characterised in further, comprising recycling between 5% and 25% of ballasted solids separated from the ballasted effluent in the solids-liquid separator to the reactor tank . <EOS>