NOVELTY - Microbial agent is prepared using bacterial suspension comprising Bacillus, Pseudomonas stutzeri, P.pseudoalcaligenes and P.oleovorans obtained from edible oil, where the suspension comprises greater than or equal to 3.8x 108 colony forming unit (CFU).    USE - The microbial agent is useful for urban domestic sewage treatment, reinforcing wetland and treating contaminated river water (claimed).    ADVANTAGE - The method reduces chemical oxygen demand (COD), ammonia nitrogen, total nitrogen and total phosphorus content in contaminated river water effluent and urban sewage effluent to reach surface water quality standards, urban sewage treatment plant standards and pollutant discharge standards.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) method for preparing the microbial agent, involves (a) inoculating Paenibacillus obtained from slant culture into 200 ml denitrifying bacterial culture medium (broth) and culturing at 30-35 degrees C under shaking condition with 180-220 rotations per minute (rpm) shaking speed for 24-36 hours to obtain activated strain broth, (b) centrifuging the broth at 5000-8000 rpm for 15-20 minutes and obtaining supernatant of bacterial cells, diluting the supernatant with sterile water to obtain suspension with 1.5 g wet cells/l of bacterial suspension, (c) preparing P.stutzeri, P.pseudoalcaligenes and P.oleovorans bacterial suspension by performing the above mentioned step and (d) mixing 4 bacterial suspensions in equal volume to obtain microbial agents, where denitrifying bacterial culture medium (1 l) is prepared by mixing 2 g sodium acetate, 0.4 g monopotassium phosphate, 0.6 g magnesium sulfate heptahydrate, 0.007 g calcium chloride, 1 g potassium nitrate, 12 ml tris(hydroxymethyl)aminomethane (tris) buffer, 2 ml microelements and remainder water and adjusting the pH of the medium to 7-7.2 and autoclaving the medium at 110 degrees C for 20 minutes; and (2) method for reinforcing wetland and treating 1 vol.% sewage water involves treating with microbial agent for greater than or equal to 7 days.