"L'égout, c'est la conscience de la ville."
"Sewer is the conscience of the city."
——Hugo Victor. Les Misérables.
Sewer networks are one of the most critical infrastructure assets for modern cities. These deep-rooted, well-connected pipes form a circulatory system that links the metabolism of the water resources. They are the lifeblood of every city's livelihood and the city manager's conscience.
SRBioquencher focuses on two main aspects in terms of social responsibility: the safety and maintenance concerns about drainage systems and the labor and social security of sewer workers.
For each of these two aspects, we investigated the current situation and proposed expected goals, and corresponding implementation paths, and listed the results and feedback we received.
By posting questionnaires on the web, we learned about the drain problems residents have experienced and how concerned residents are about the urban drainage system. Based on the results of the analysis of 487 questionnaires, we found that 56.47% of residents have smelled odor from overflowing sewer pipes in their living area, and 60.37% of residents have had problems such as clogged or damaged drains at home.
In response to questions about the safety and maintenance of the city's drainage system, residents expressed their concerns about blockage, leaks, explosions, waterlogging, loose manhole covers, etc., with blockage, explosions, and waterlogging being the three biggest concerns.
Fig.1 A word cloud map about residents' concerns about the drainage system
For project design:
For human practice:
By consulting Mr.Ouyang and Mr. Ran, experts in the maintenance of urban drainage systems from Chengdu Xingrong Municipal Facilities Management CO., LTD.. We learned that inspectors inspect the external conditions of manhole covers twice a day, mainly to avoid dangers such as missing and loose manhole covers. In addition, internal inspections of pipelines will be carried out across the city before and after floods every year to comprehensively check the situation of the pipelines and complete dredging.
Municipal facilities management departments have extensive measures and strict implementation standards for pipeline maintenance and safety assurance. In order to monitor the flammable gas in sewers, the municipal department has installed real-time monitoring and alarm devices in the pipelines. According to the Technical requirements of gas monitoring for sewer and septic tanks of the People's Republic of China, when the methane concentration in the pipeline exceeds 5%, the alarm will automatically sound, and sewer workers will go to the site to deal with it in time to avoid an explosion.
For pipe corrosion, Mr.Ouyang explained that there are different treatment methods for different types of corrosion. On the scene, pipeline maintenance personnel will record on-site situation and conduct condition assessment and select appropriate treatment methods in strict accordance with the Technical specification for inspection and evaluation of urban sewer of the People's Republic of China.
For hydrogen sulfide gas leakage in residential areas, Mr.Ran said that hydrogen sulfide gas leakage sometimes occurs near septic tanks and it is normal. If there is constant sewage odor in a district, the cause is often an overflow due to excessive gas from poorly designed pipelines in the early stages. Or the odor may from a clogged drain where sewage collects, in this case community officials should call the municipal company for dredging. In addition, Mr.Huang from Chengdu No. 4 Water Reclamation Plant expained that the hydrogen sulfide gas concentration around the wastewater plant is tested regularly to avoid the spillage of hydrogen sulfide affecting the residents' health and daily life.
Fig.2 Posters produced and posted on community bulletin boards
If the concentration of hydrogen sulfide in the sewer environment exceeded the 'threshold' value, it would do harm to sewer workers.
By consulting the occupational disease specialist, Dr.Fu from West China Hospital of Sichuan University, we learned that hydrogen sulfide, as a neurotoxic gas, only causes acute poisoning, not chronic poisoning, so there are only cases of acute poisoning in clinical practice. Hydrogen sulfide brings comprehensive damage to the body and mainly causes acute cardiac damage, causing respiratory and cardiac arrest, and carotid sinus syndrome.
Hydrogen sulfide poisoning is treated following the guidance of Diagnostic Criteria of Occupational Acute Hydrogen Sulfide Poisoning. Dr. Fu said that more than 10 years ago, there were more cases of hydrogen sulfide poisoning, mainly occuring in sewer dredging, natural gas desulfurization, sulfuric acid production or leather and other related industries. In recent years, with increased security awareness and technological innovations, the cases of hydrogen sulfide poisoning have greatly reduced.
Fig.3 Consulting occupational disease specialist, West China Hospital of Sichuan University, Chengdu
To further understand the labor and social security of sewer workers, we first consulted with the supervisors of the municipal corporation's drainage pipe maintenance. Then we interviewed the sewer workers from Chengdu Xingrong Municipal Facilities Management CO., LTD. We also went to the working scene and made a documentary featuring sewer workers' daily work.
According to feedback from Mr.Ran, the municipal corporation provides its workers with adequate labor security. The current physical examination has not found that sewer gases harm sewer workers, but it is uncertain whether working in this job for a long time will hurt physical well-being.
Dr. Fu explained there are generally three types of medical examinations for sewer workers: on-duty, off-duty, and emergency. There are no specific examinations for Hydrogen sulfide inhalation on the list of routine physical examination, for it only causes acute damage. Only in emergency physical examinations can hydrogen sulfide poisoning be carefully diagnosed.
At the dredging site, we learned about the dredging procedures. After removing the manhole cover, workers will introduce a large amount of air into the sewer until the concentration of harmful sewer gases like hydrogen sulfide reach a harmless level. Before starting work, workers get dressed in work clothes, then the team leader will reiterate the safety regulations, and workers need to sign them. Workers will go down into the sewers only after putting on protective gear, and another worker will ensure the safety of those going down the pipes throughout the process.
During the interview, we learned about workers working routines and their safety concerns. Sewer workers are usually busier when conducting pre- and post-flood inspections. The rest of the time, they are on call day and night. When it comes to safety concerns, the workers said that they all received professional training before taking up the job. And with professional equipment and other workers to ensure their safety, they are not worried.
The difficulty of the work is that the diving suit is relatively heavy and the space inside the pipes is relatively narrow, humid, and hot, and it is easy to become physically exhausted. Mr. Ran explained that robots can solve most sewer problems, but the clogged pipes need sewer workers to get into them to dredge.
Mr.Ran also hopes to use the platform of SCU-China to appeal to citizens to be "friendly" to drainage facilities, not to dump items that may clog the pipes into the sewers, and to appreciate the hard work of sewer workers.