<p>In this study, we investigated the effects of combined conditioning of water treatment sludge (WTS) with activated persulfate on enhancing dewaterability, phosphorus enrichment, and heavy metal stabilization during sludge treatment. The optimal parameter combinations obtained by Response Surface Methodology were 0.63 mmol/g DS of sodium persulfate (SPS), 0.61 mmol/g DS of Fe²⁺ and 50% DS of WTS. The SRF reduction of the conditioned sludge was increased to 93.51%, with a net sludge yield of 6.78&#xa0;kg·m^− 2·h^− 1 and a compressibility coefficient of 0.62, demonstrating excellent dewaterability. Through characterization such as Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometry (XRD), it was found that the inorganic content of the sludge increased and the form of phosphorus existence changed after composite conditioning. The phosphorus concentration in the liquid phase of the sludge system was drastically reduced from 168.68&#xa0;mg/L to 2.61&#xa0;mg/L, which greatly enriched phosphorus in the sludge cake. The heavy metals were transformed to a stable state, reducing the leaching toxicity of heavy metals. Therefore, this combined conditioning provides an effective strategy in the field of sludge treatment, which not only improves the dewaterability of sludge but also reduces the environmental risk of heavy metals in the sludge.</p>