It is inevitable that there will be dangers in the process of sewage treatment! Therefore, the staff need to be particularly cautious and careful during the engineering process. So as to avoid a series of unnecessary troubles. When it comes to life, sewage treatment and online water quality monitoring must be taken seriously to minimize the occurrence of accidents as much as possible. Why do you say so? After reading this article, you may have some understanding.
Not to mention anything else, there are already quite a few toxic and harmful substances in the sewage pool alone! Let’s take a look together.
- Type of sewage tank
1) By location: indoor, semi-outdoor and outdoor
2) Classified by the setting of the sewage tank: single-unit setting above ground level and underground setting below ground level.
3) Classified by the setting of the sewage cleaning device: fully automatic mechanical cleaning, semi-automatic mechanical-assisted manual cleaning, and manual cleaning.
4) By type of sewage: sewage from electroplating and circuit board manufacturing enterprises, sewage from leather and papermaking enterprises, sewage from dyeing and printing enterprises, domestic sewage, septic tank sewage, etc.
- Common toxic substances in various types of sewage ponds:
The wastewater from electroplating and circuit board manufacturing enterprises mainly contains heavy metal compounds such as chromium, cadmium, nickel, zinc, copper, gold and silver, cyanide (including “gold salts” used in cyanide electroplating and arsenic), arsenic compounds (arsenic trioxide), and corrosive acidic and alkaline substances (used for the sedimentation and neutralization of heavy metals in wastewater).
2) The wastewater from leather and papermaking enterprises, dyeing and printing, etc. mainly contains: heavy metals such as chromium, cadmium and barium and non-metallic compounds (leather tanning, dyes, etc.), hydrogen sulfide and methane, ammonia, carbon dioxide (generated from the decomposition of organic matter such as leather, paper and natural fibers, etc.), and corrosive acidic and alkaline substances (used for the sedimentation and neutralization of heavy metals in the wastewater, etc.)
3) Domestic sewage, septic tank sewage, etc. mainly include: hydrogen sulfide and methane, carbon dioxide, ammonia (generated by the decomposition of various organic substances, etc.)
In addition, for sewage ponds located underground, due to natural laws, carbon dioxide naturally deposits in the air at the bottom.
- Main damages caused by toxic substances in sewage tank cleaning:
Poisoning caused by irritating and asphyxiating gases: hydrogen sulfide (irritating and asphyxiating), methane and carbon dioxide (asphyxiating alone), hydrogen cyanide (asphyxiating, formed by the contact of high-concentration cyanide with acid), ammonia (irritating and corrosive), etc. This is the main cause of casualties among sewage pool cleaning personnel.
2) Poisoning caused by highly toxic substances: Cyanide, arsenic compounds (arsenic trioxide), etc. entering the mouth, eyes and broken skin by mistake are the secondary causes of casualties among sewage pool cleaning personnel.
3) Corrosion caused by acidic or alkaline substances: To the eyes, skin, etc., this is the main cause of injury to the personnel cleaning the sewage pool.
4) Allergic reactions caused by heavy metal compounds, dyes, etc. : Through irritation to the skin and mucous membranes, some substances can enter the body through broken skin and further cause poisoning. This is a secondary cause of injury to personnel cleaning sewage ponds.
- Characteristics of the main toxic gases and hazardous factors of toxic substances:
1) Hydrogen sulfide
It is the main cause of acute poisoning safety production accidents in this industry. Hydrogen sulfide exists as a colorless gas with a smell of rotten eggs at normal temperature. It is soluble in water and can explode when its concentration in the air reaches 4.3% to 45.5%. This gas is not only an irritating gas but also a strong neurotoxic asphyxiating gas. At low concentrations (30-300mg/m ³), it can cause symptoms such as tearing, coughing, dizziness, headache, chest tightness, fatigue, nausea and vomiting after exposure. At medium concentrations (300-700mg/m ³), after exposure, in addition to prominent symptoms such as dizziness, headache, chest tightness, fatigue, nausea and vomiting, it can also cause limb movement disorders and temporary consciousness disorders. At high concentrations (above 700mg/m ³), after exposure, it can directly act on the brain’s nerve center through the chemical sensory organs in the human body, causing respiratory paralysis or further cessation and abnormal heartbeat and further cessation, resulting in delirium, convulsions, rapid coma, etc., leading to “lightning-like” coma or death (above 1000mg/m ³), and at the same time. Accompanied by pulmonary edema. In addition, hydrogen sulfide also has cytotoxic effects, causing symptoms similar to cyanide poisoning. Even after being sent to the hospital for treatment, the condition may worsen and death may occur due to this cause.
2) Methane
It is the main cause of acute poisoning safety production accidents in this industry. Methane is a colorless and odorless gas at normal temperature, lighter than air, and can explode in the air. This gas is a simple asphyxiating gas and has an anesthetic effect. When the air concentration reaches 25% to 30%, brief inhalation can cause symptoms such as dizziness, headache, chest tightness, fatigue, nausea and vomiting. After continued inhalation, in addition to prominent symptoms such as dizziness, headache, chest tightness, fatigue, nausea and vomiting, it can also cause limb movement disorders and temporary consciousness disorders. When inhaled in large quantities, it can directly act on the brain’s nerve center through the chemical sensory organs in the human body, causing respiratory paralysis or further cessation and abnormal heartbeat and further cessation, resulting in delirium, convulsions, rapid coma, etc., leading to “lightning-like” coma or death.
Acute poisoning caused by sewage treatment ponds and construction Wells is not only due to the accumulation of the above two gases and their escape from the sewage during daily stirring, but also because of the hypoxia caused by the above gases.
3) Carbon dioxide
It is a secondary cause of acute poisoning safety production accidents in this industry. Carbon dioxide exists as a colorless and odorless gas at normal temperature. It is heavier than air and non-flammable and non-explosive. This gas is a simple asphyxiating gas, with a content of 0.03% in natural air. At low concentrations, it has an excitatory effect on the respiratory center, while at high concentrations, it has an inhibitory effect on the respiratory center. Acute poisoning is often accompanied by hypoxia. Therefore, the so-called carbon dioxide poisoning in daily life is not simple; in fact, it is jointly caused by hypoxia. High concentration inhalation for a short period of time can cause symptoms such as dizziness, headache, chest tightness, fatigue, nausea and vomiting. Continued inhalation may cause limb movement disorders, temporary consciousness disorders, etc. When inhaled in large quantities, it can directly act on the brain’s nerve center through the chemosensory organs in the human body, causing respiratory paralysis or further cessation, abnormal heartbeat and further cessation, resulting in delirium, convulsions, and rapid coma, leading to death.
4) Cyanide, hydrogen cyanide
It is a secondary cause of acute poisoning safety production accidents in this industry. Sodium cyanide (xanthate), potassium cyanide and other substances in cyanide are highly toxic. Potassium ferrocyanide (yellow blood salt), iron ferrocyanide (Prussian blue), potassium ferrocyanide (red blood salt), etc. are of low toxicity, but they release highly toxic hydrocyanic acid when exposed to acid. Cyanide generally does not cause poisoning except when it accidentally enters the mouth, eyes or breaks the skin. Hydrocyanic acid is a colorless, bitter almond-like liquid that releases highly toxic vapor. Hydrogen cyanide exists at room temperature as a colorless gas with a bitter almond-like odor. All inorganic cyanide substances are strong blood-toxic asphyxiating substances. Even a very small amount can cause symptoms such as dizziness, headache, chest tightness, fatigue, nausea and vomiting. Severe poisoning can lead to immediate death. Inhalation of high-concentration hydrogen cyanide gas (300mg/kg) for a short period of time causes immediate death.
5) Arsenic compounds, arsine
It is a secondary cause of acute poisoning safety production accidents in this industry. Arsenic trioxide (arsenic trioxide) in arsenic compounds is a highly toxic substance, while arsenic pentoxide, arsenic trisulfide (orpiment), and arsenic disulfide (realgar) are of lower toxicity. Arsenic compounds release highly toxic arsine when exposed to acid. Arsenic, which is highly toxic, generally does not cause poisoning except when it accidentally enters the mouth, eyes or breaks the skin. Arsine is a colorless gas with a garlic-like odor that exists at room temperature. Arsenic substances are strong hemolytic poisons, mainly causing damage to the kidneys, and also have a damaging effect on the heart, liver and skin. Inhaling a small amount of arsine can cause symptoms such as dizziness, headache, chest tightness, fatigue, nausea and vomiting. Severe poisoning can lead to immediate death. Inhalation of high-concentration arsine gas (250ppm) for a short period of time causes immediate death, and inhalation of 25-50 PPM for 30 minutes also leads to death.
6) Ammonia gas
It is a secondary cause of acute poisoning safety production accidents in this industry. Ammonia exists at normal temperature as a colorless, urine-smelling, and irritating gas. It mainly causes irritation and corrosion to the upper respiratory tract, and in severe cases, it can lead to chemical pneumonia, pulmonary edema, and even acute pulmonary hemorrhage, pneumothorax, emphysema, etc. It can also cause burns and damage to the eyes and skin. Inhaling a small amount of ammonia gas (above 100mg/m ³) can cause upper respiratory tract irritation symptoms, such as coughing, tearing and runny nose, chest tightness, fatigue, nausea, vomiting, laryngeal edema, breathing difficulties, etc. Severe cases (1750-4500mg/m ³) can immediately lead to chemical pneumonia, pulmonary edema, and even death.
To sum up, we can understand the severity of water pollution and what impacts it will bring. In addition to attaching importance to water treatment, the staff also need to monitor various indicators in the water in real time through water quality detectors, so as to determine whether the indicators in the water are qualified and then see if it is suitable for discharge.
