Microbial electrolysis followed by chemical precipitation for effective nutrients recovery from digested sludge centrate in WWTPs

•MEC followed by chemical precipitation was studied for N&P recovery from centrate.•Inadequate biodegradable COD in centrate led to ineffective N recovery in MEC.•Centrate was mixed with sludge fermentation liquor to enhance N recovery in MEC.•Recovered H2 gas was adequate to offset the electricity cost of MEC operation.•P was efficiently recovered from MEC anodic effluent using Ca2+ or Mg2+ salts.