Places of corrosive gas generation in the sewerage network

Summary

The factors that affect the generation of corrosive gases in the wastewater disposal system, saturation of the gas air environment with corrosive gases in sewers are considered. A number of structural components as well as hydraulic patterns of wastewater flow, its physical properties that enhance the gas generation processes are considered and described. The evaluation and prediction of the places of corrosive gas generation and emission provide for forecasting the measures focused on the reduction of the negative impact of emissions or their complete elimination. The operating services carry out regular sewer network monitoring with the purpose of detecting the places of emission generation. The future work of the services is limited to the isolation of corrosive gases by redistribution in the network, disposal into the atmosphere, neutralization or purification. The results of introducing the design of a pipe drop with a dead blanking in the lower part of the sewer shaft, ejector and pipe air vent are presented.

Key words

sewer , sewerage network , shaft , gas emission , corrosive gases , gas generation

Detecting the places of corrosive gas emissions from sewers to the surface and conditions of their formation

Summary

Corrosive gas emissions from sewers to the surface happen because of the excess pressure increase in the underroof and shaft space of the sewer. The causes of the pressure increase in the shaft space are considered. The gas amount changing during entering the shaft and removed from it depends on the wastewater flow rate, sewer filling (the height of the gas flow), hydraulic gradient of the sewer, formation of stagnation zones (sludge sedimentation), and temperature. Variation of these parameters and thus the location of corrosive gas emissions to the surface depend on a number of factors that can be divided into several groups: construction, hydraulic, geodesic, operation, random, climatic. Reducing the gas emissions from sewers is possible by: introduction of construction solutions for gaseous medium redistribution; elimination of air blocks, installation of purification filters; avoiding deviations from the design solutions arising during the construction of deep sewers; proper management of wastewater flow at elevation differences; improvement of the sewer operation rules, severization of the requirements to the operating personnel qualification.

Key words

collector , sewerage network , joint movement of liquid and gas , gas emission , excess pressure , ventilation