Simultaneous sludge degradation, desalination and bioelectricity generation in two-phase microbial desalination cells

The invention of solid phase bioelectrochemical systems (SPBESs) provides a promising method for synchronous dehydrated sludge compost, desalination and bioelectricity generation. However, low power density and anodic salinization are common problems in SPBESs. A two-phase microbial desalination cell (TPMDC) could achieve simultaneous desalination of saline solution and dehydrated sludge by adding concentration chambers. Experimental results indicated that the D_salt in 3 d for different concentration saline solutions were 6.00 ± 0.05% (35 g L⁻¹), 10.75 ± 0.76% (10 g L⁻¹), and 19.80 ± 0.64% (2 g L⁻¹) respectively during the stable operation period of TPMDC. The D_salt of anodic sludge reached 31.63 ± 1.26% after 200-day operation, and the removal of organic matter was up to 32.70 ± 1.67%. The P_max (1.97 ± 0.33 W m⁻³) was produced on 52 d with open circuit voltage (OCV) of 0.998 ± 0.011 V. After bioelectrochemical stabilization, the feasibility of dehydrated sludge land application was improved. Specifically, the dehydrated sludge humication level significantly enhanced, the contents of available nitrogen, phosphorus and potassium all increased, the heavy metals and metalloids in dehydrated sludge transferred into stable residual form, and phytotoxicity of dehydrated sludge decreased. BES as a pretreatment of dehydrated sludge composting has great potentials.