Analysis of the operation of acidifiers after the reconstruction of the block of the Liuberetskie Wastewater Treatment Facilities

Summary

Municipal wastewater in Moscow after primary settling contains insufficient organic matter for the sustainable removal of nitrogen and phosphorus to the standard quality during treatment. Therefore, while designing the reconstruction of the old block of the Liuberetskie Wastewater Treatment Facilities in Moscow, the acidification (prefermentation) method was chosen as the most efficient process solution for enriching wastewater with easily decomposable organic matter (obtaining organic acids during acidic fermentation of raw sludge from primary settling tanks). Upon the completion of the reconstruction of the old LWWTF block at the end of 2021, primary sludge acidifiers were put into operation. Launching acidifiers provided for enriching primary water with easily decomposable organic matter (volatile fatty acids, including acetate) resulting in the improved efficiency of denitrification and biological dephosphorization processes in the aeration tanks. Two or three weeks after the acidifiers had been put into the operation mode, the quality of effluent for nitrogen as nitrates and phosphorus as phosphates was meeting the MPC for fisheries. The process parameters of the acidifiers (hydraulic retention time, residence time for dry matter, the rate of volatile fatty acids formation, the degree of recirculation, the dry matter concentration in the incoming flow) corresponded to those recommended in the literature. Possible situations of abnormal operation of acidifiers have been analyzed and recommendations have been developed to eliminate the causes.

Key words

nitrogen removal , wastewater treatment , acidification , readily available organic matter , prefermentation , phosphorus elimination , process parameters of the acidifiers’ operation

Acidification potential of the incoming wastewater and raw sludge at the Moscow wastewater treatment facilities

Summary

The consistency of biological phosphorus elimination process depends on the readily available organic matter concentration in the incoming wastewater. The concentration of this substance in the wastewater at the Moscow wastewater treatment facilities is not high. Acidification is one of the methods of enhancing readily available organic matter concentration. The production of biologically readily available organic matter (volatile fatty acids) of raw sludge and incoming wastewater at the Kouryanovo Wastewater Treatment Facilities was evaluated in an anaerobic batch-flow reactor at various temperature and time values of prefermentation process. On the basis of the experimental results the techniques of evaluating the availability of the organic compounds for phosphate accumulating bacteria (the technique of evaluating acidification potential) was developed. Acidification potential provides for the assessment of acidification process efficiency for the reduction of phosphate-phosphorus in the effluent.

Key words

acidification , acidification potential , readily available organic matter , prefermentation , phosphorus elimination

The experience of upgrading wastewater treatment facilities of Zhigulevsk

Summary

The experience of designing, constructing and upgrading wastewater treatment facilities (16,200 m³/day) in Zhigulevsk, Samara Area is described. Prior to the reconstruction the technical condition of the facilities was satisfactory. However, the effluent quality parameters exceeded the maximum permissible levels for BOD, suspended solids, nitrogen compounds, phosphates and oil products. The efficiency of primary settling related to BOD₅ and suspended solids was about 50% resulting in BOD_full: total mineral nitrogen: phosphorus of phosphates ratio changing from 100:12.5:1.7 to 100:21.8:3.16. Despite the deterioration of this primary effluent parameter in the process of nutrients removal it was decided to retain primary settling in the design layout because of the insufficient capacities of the existing aeration tanks. The technology of nitrification-denitrification with anoxic and aerobic zones and chemical phosphorus removal is suggested. The bioreactor capacity was increased 1.5 times by establishing the third process line in addition to the existing ones; besides the construction started from the nitrification-denitrification aeration tank to provide for the sustainable effluent quality for the entire reconstruction period.
For tertiary treatment a filter-bioreactor with a brush head was used. Disinfection is carried out by UV-irradiation in a trough-type unit without changing the gravity effluent flow. The design documentation was approved by the state expertise of the construction projects. By now a considerable part of the facilities has been constructed and put into operation. The successful experience of Zhigulevsk wastewater treatment facilities reconstruction carried out without interruption of wastewater inflow can be overspread among the similar projects in medium-scale cities of the central part of Russia.

Key words

reconstruction , wastewater , biological treatment , nitrification , sewerage treatment facilities , denitrification , phosphorus elimination