Temperature effect on nitrification processes in activated sludge

Summary

Temperature has been an important factor affecting the efficiency of biological nitrogen removal by activated sludge at wastewater treatment facilities. A laboratory SBR reactor was used in the experiments; activated sludge for cultivation was obtained from aeration tanks of the municipal wastewater treatment facilities. The taxonomic composition of bacteria in activated sludge was determined by high throughput sequencing of the DNA section encoding 16S rRNA. The nitrification rate was determined at water temperatures of 1, 5, 8, 11, 17, 19 and 21°C. Nnitrifying bacteria Nitrosomonas spp. and Nitrospira spp. were found in activated sludge with the abundance of 0.07% and 0.34%, respectively. The maximum nitrification rate observed at 21 °C was 4.3 mg N–NO₃ per 1 g of ash-free substance of activated sludge per hour. The nitrification rate decreased with decreasing temperature and was 0.3 mg/(g·h) by N–NO₃ at 1°C. The results of the study can be used as a theoretical basis for optimizing the operation of the treatment facilities in areas with low temperatures to improve the efficiency of nitrogen removal from wastewater.

Key words

wastewater , nitrification , activated sludge , temperature , biological removal of nitrogen

Features of wastewater composition at small-scale treatment facilities

Summary

The composition of wastewater at small-scale treatment facilities differs significantly from the composition of municipal wastewater both in terms of pollution concentrations and their proportions. Information is presented on the collection and analysis of data from long-term observations of the composition and temperature of wastewater from small settlements at 31 treatment facilities. It has been revealed that an increased concentration of nitrogen at medium concentrations of organic substances is typical for these facilities. Such a disproportion results in a shortage of substrate for biological treatment – denitrification; consequently, dosing an external source of organic matter is required. Wastewater supplied to the treatment facilities has a very low N–NH₄/N_total ratio, which indicates incomplete ammonification and the need to take into account total nitrogen during laboratory control. At some facilities, the temperature of incoming wastewater is below 10–12°C during most of the year, which significantly reduces the efficiency of biochemical treatment processes.

Key words

domestic wastewater , sewerage treatment facilities , temperature , wastewater composition , denitrifying potential

Temperature and pressure monitoring system of the water distribution networks of Yakutsk

Summary

The information on the design of the system of monitoring temperature and pressure in the water distribution networks of Yakutsk is presented. In operating the municipal water supply under low temperature conditions continuous water temperature and pressure monitoring in the network is needed to prevent from pipeline freezing and overheating of the pumped water. To this end automated systems of temperature and pressure monitoring in the networks have been developed. To provide for the data remote transfer for the system control Circuit Switched Data (CSD) technology for GSM mobile networks is used. With the help of this technology two GSM modems can establish a communication channel for import of data. For the operation of this system at a remote measuring point a cellular communication signal of the selected operator at the facilities together with continuous power supply shall be available. AIR-10N pressure sensors and TSPU-205-N temperature sensors were used as transmitters with 4–20 mA standardized signal; CPU – computer-process interface modules manufactured by Elemer SPE OJSC were used for subsequent transformation of signal and interface. Exchange of data between the computer and analogue input modules is ensured by MODBUS protocol version. To provide for the system control an information computerized system including a data base with Microsoft SQL Server 2008 Express, a service of terminal polling with the help of Windows service application, and an operator interface was developed. At present the system is operating steadily in the mode of systematic polling. The designed system can provide for collecting data from 200–300 measuring points.

Key words

water supply , monitoring , pressure , pipeline , centralization of control , temperature