Most microbial desalination cells (MDCs) in previous research were constructed of three chambers fed with municipal wastewater as anolyte. In the present study, a unique design of MDC, named quadripartite microbial desalination cell (QMDC), was designed and fabricated to demonstrate the feasibility of a 9-chamber MDC for co-treatment of septage (septic tank sludge) and municipal wastewater. It was found that maximum power density, COD removal in anode chamber, and desalination rate at the COD concentration of 4911.6 +/- 71 mg L-1 (mixing ratio of 1:10) were 8.16 W m(-3), 58.4%, and 72.8% over a short-term operation; corresponding data in QMDC containing lower COD concentration (mixing ratio of 1:100) decreased to 7.2 W m(-3), 49.8%, and 69.7%, respectively. In addition, longer operation of QMDCs showed a significant drop in the performance of QMDC fed with higher fraction of septage (mixing ratio of 1:10). Regarding COD removal, transferring treated anolyte solution from anode to cathode chamber improved total COD removal by 91.1%. It was found that although QMDC performance in electricity production and salt removal was relatively better in mixing ratio of 1:10, the use of higher mixing ratio (1:100) is firmly suggested because of higher stability of the process under long-term operation.