MicroCat-XNC restores nitrification in Municipal wastewater treatment plant

A municipal wastewater treatment plant in a major town in the one of the Baltic Republics experienced a complete loss of nitrification during the recent winter. The main reasons for the loss of nitrification was the rapid drop in temperature of the influent, sludge washouts during periods of heavy rainfall in the autumn, industrial discharges and landfill leachate in the influent and high ammonium levels in secondary influent from the anaerobic sludge digesters.

The plant layout is an activated sludge system which consist of primary clarifiers; biological treatment plant – anaerobic zone, denitrification zone, nitrification zone; secondary clarifiers. The wastewater flow through the treatment plant on average is app. 2000 m³ per hour and during the autumn and/or spring rainfalls the wastewater volume was increasing.

QM Environmental Services distributor in the Baltic Republics, Ekotakas UAB, was called in to offer a solution in order to restore the nitrification in this treatment plant as several other measures failed to achieve this. After studying plant data a program was designed comprising operational changes like increasing the sludge concentration to >4,5 mg/l and sludge age to 30 days, reducing the recycle rate between denitrification and aeration zones and dosing of MicroCat-XNC.

MicroCat-XNC is a refrigerated slurry concentrate of preselected, adapted nitrosomonas and nitrobacter microbial strains for use in biological wastewater treatment plants receiving wastes containing ammonia. Under toxic and/or cold-weather conditions, the growth rate of natural nitrifying populations tends to slow appreciably, allowing ammonia to pass through the system. MICROCAT-XNC synergistically combines the capability of several natural ammonia-oxidizing microbial strains for reseeding nitrifying systems and enhancing performance under toxic, inhibitory or cold-weather conditions. When used on a preventive maintenance basis, MICROCAT-XNC can improve the consistency ofongoing nitrification and improve overall system performance. MICROCAT-XNC is formulated specifically for use by the chemical, food processing, petroleum refining, primary metals, textile and related industries and for use in municipal plants receiving wastes containing ammonia.

An initial start-up program of 30 days was followed by a small daily maintenance dose for another 28 days. MicroCat-XNC was prior to dosing into the aeration zone reactivated by diluting it in mixed liquor from the aeration zone and aerating it during at least 8 hours in order to increase the concentration of nitrification bacteria. In total an amount of 240 kg MicroCat-XNC was dosed.

After a period of one month of dosing the nitrification started to return, this corresponded with the sludge age. A spike in influent ammonium after 17 days into the treatment program was already effectively degraded showing only a small increase in ammonium levels in the effluent. Within 2 months after start of the program, full nitrification was restored with ammonium removal rates above 95% despite ongoing industrial, landfill leachate and anaerobic digester filtrate discharges and sludge washouts due to poor sedimentation.

For more information on how MicroCat-XNC can restore or maintain nitrification contact QM Environmental Services.