By Wissam Hamdi
Solid wastes resulting from sewage, such as sludge, are among the most dangerous concentrated wastes. They are characterised by a high degree of toxicity. This is why there are links between the use of untreated sludge in agriculture and food production, on one hand, and various diseases, such as liver disease; kidney failure; cancer, and typhoid, on the other.
Each one acre of farmland needs about 20 cubic metres of organic fertiliser produced from animal waste (manure), according to Ministry of Agriculture data. However, the production of this type of fertilizer covers the needs of only half of the farmland in Egypt.
Chemical fertilisers that contain nitrogen, potassium and phosphorus are generally known to be costly. Therefore, untreated sludge seems to be the miraculous alternative to these fertilisers, due to its low cost, according Ahmed Attia, professor of agricultural production at Mansoura University.
Schoolteacher Sobhi Hassan Abdel Qader, 65, from Aga city, Mansoura Governorate, had contracted typhoid for the second time in 2019. Abdel Qader’s body temperature rose sharply as it did the first time in 2015. He suffered from severe abdominal cramps and loss of appetite, with constant vomiting followed by diarrhea due to indigestion. This affected his nerves and movement. Doctors diagnosed Abdel Qader with typhoid and told him that this condition was caused by a stomach bug. They prescribed antibiotics to eliminate the germ. Nonetheless, the antibiotics could only relieve the pains, Abdel Qader said.
He could not sit normally and his weak nerves restricted his movement to the point where he could not make the slightest move at home. “I had to consult another doctor” Abdel Qader said. This other doctor asked him to stop taking the medicines prescribed by the previous doctor. He also prescribed another type of antibiotics. “I recovered, but it took me a month and a half for this to happen” Abdel Qader said.
If transmitted to humans through plants and exceed specific ratios, the heavy elements residing in sludge cause the aforementioned adverse health effects, especially among children.
Biology and environmental health professor Khaled al-Qadi referred to the presence of enough laws that criminalise working with sludge without treating it. “There are conditions for the use of untreated sludge,” he said. He said the elimination of biological contamination and dangerous chemical pollutants is the first of these conditions. As for the heavy elements, including lead, cadmium and chromium, he added, they are produced by iron, fertilisers and paint factories.
Lead causes 32 diseases, such as paediatric leukaemia, women’s infertility, fatal eformity, impaired memory, child retardation and anaemia, al-Qadi said. He added that chromium weakens heart muscles. The outbreak of typhoid happens because of direct exposure to the sludge salmonella which is found in human sewage waste.
According to Adel Abdel-Fattah Omran, an environmental engineering researcher and a consultant at the Department of Chemicals, Materials and Hazardous Waste at the Environmental Affairs Agency, the safe handling of sludge requires that the percentage of lead does not exceed 300 milligrams each per kilogram of this waste, provided that it is used only in the cultivation of tree forests, woody plants and plants that are not eaten raw or used solely for industrial purposes. It is also forbidden to sell sludge inside sewage plants, because, according to the law, it is a dangerous substance, Omran said. He added that the sale of this substance requires the presence of representatives of the Environmental Affairs Agency and the Ministry of Health to ensure safe use.
Professor ofoccupational and environmental medicine and former director of the Toxicology Centre at the College of Medicine at Cairo University Dr Amal al-Safti said the dangers of untreated sludge lie in complex toxins, including lead and arsenic, which affect the immune system, cause diseases of the nervous system and affect the hormonal glands. She added that children are more affected than others by lead in the untreated sludge. This happens because of direct effects on the brain and the rest of the nervous system among infants, Safti said. She referred to other effects on endocrine functions.
The Ministry of Health and Population ‘Decree No. 214/2018 focuses on the health requirements for selecting sites for the construction of sewage treatment plants. This decree stipulates that the distance between the plant and any residential communities should not be less than 500 metres and may reach 10 kilometres, depending on the size of the plant to avoid the environmental and health damage that it causes, according to Abdullah al-Erian, a professor of urban planning at Cairo University.
He called for establishing plants based on wind direction to prevent the migration of any microbes or bacteria to population concentrations. Helmy al-Zanfali, researcher at the National Research Centre, pointed to the presence of large amounts of sludge. This sludge, he said, is rich in everything plants need.
The problem in Egypt is that the cultivated space is limited al-Zanfali said. This makes it necessary for us to increase production by resorting to land reclamation in areas, such as the New Delta and El Alamein, which are all sandy, he added.
He noted that sanitation does not pose dangers to humans in terms of sludge containing heavy elements. However, he added, mixing sewage with industrial drainage is the main cause of heavy elements and poses a threat to agriculture and health.
He called for stopping mixing industrial sewage with sewage before treatment. This is only when this sewage can be used as fertiliser at the lowest cos, al-Zanfali said. He also called for utilising modern technologies in transforming untreated sludge into safe and profitable organic fertiliser. In this way, we can overcome a huge environmental problem and make a safe and sustainable use of wastes to serve the goals of sustainable development, al- Zanfali added.
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