The objective of development of small-scale on-site wastewater treatment for riverside restaurant were to compare the treatment efficiency of Septic+Aerobic fixed-film reactor system with hydraulic retention time (HRT) 56 (32+24) hours and Septic+Submerged anaerobic+Aerobic fixed-film reactor systems with HRT 68 (32+18+18) and 80 (32+24+24) hours, respectively. Each system was fed by riverside restaurant wastewater with flow rate 3.0 m[superscript 3]/d and organic loading rate 2.4 kg BOD/m[superscript 3]-d. The experiment was repeated 16 times. Moreover, in the order to find out the best system for treated wastewater from riverside restaurant in the economic aspect. The results indicated that the efficiency of BOD, suspended solids, settleable solids, total dissolved solids, sulfide, TKN and grease and oil of the Septic+Aerobic fixed-film reactor system were 95.14, 95.48, 99.55, 15.37, 96.95, 94.60, and 94.61%, respectively, The Septic+Submerged anaerobic+Aerobic fixed-film reactor system with HRT 32 + 18+18 were 95.17, 97.13, 98.95, 92.84, 25.40, 98.12, and 87.37%, respectively, and the Septic+Submerged anaerobic+Aerobic fixed-film reactor system with HRT 32 + 24 + 24 hours were 95.76, 98.11, 97.34, 93.98, 13.41, 97.35, and 99.06%, respectively. The study revealed that all of 3 systems were not significantly difference effective for treating wastewater from riverside restaurant, except the efficiency of the systems which consist of the submerged anaerobic system were high removing TKN, significant (p<0.05), and the system which had HRT 32 + 18 + 18 hours treated total dissolved solids better than another systems (p<0.05). However, the experiment observed that all of parameters in the effluent of those small-scale on-site wastewater treatment systems were passed the standard of Building Effluents Standards (categories D) of the Pollution Control Department, except total dissolved solid. In the economic aspect found that the lowest cost system was the Septic+Aerobic fixed-film reactor system with HRT 56 (32+24) hours. In conclusion, the Septic+Aerobic fixed-film reactor system with HRT 56 (32+24) hours was suitable in efficiency and economic aspects for used as the small-scale on-site wastewater system for river side restaurant.