An article published in theweekly business pages of Dawn (Sept 9) said Hub Power (Hubco) planned to set up a wastewater treatment plant in Karachi that would turn 50 million gallons per day (MGD) of wastewater fit for industrial consumption.
A separate report in Dawn (Aug 23) quoted Sindh Industries Minister Jam Ikramullah Dharejo as saying that the Rs3 billion scheme for installing five combined effluent treatment (CET) plants for industrial wastewater had been jointly approved by the provincial and federal governments. The project is being executed by the Karachi Water and Sewerage Board (KWSB).
It further said that the CET plant in Korangi Industrial Area, the only plant in Karachi, is not functional. Nearly 96 per cent of industries do not have the effluent treatment facility.
Industrialists in Karachi should be thankful to the Sindh government, which is providing them with industrial wastewater treatment plants. According to the polluter-pays principle, it is the responsibility of industrialists to treat industrial wastewater.
CET plants have been installed and are in operation in numerous industrial clusters in a neighboring country. They reduce the effluent treatment cost, provide better collective treatment and control the land cost for small-scale industrial facilities that cannot afford individual treatment plants of their own. Optimum working conditions for the treatment of effluent that are up to par with discharge standards is a major mandate for any CET plant.
Textile industries discharge a high effluent load, which will make a CET plant non-functional
CET plants are actually municipal wastewater treatment plants. They only treat municipal (domestic) wastewater. A typical plant consists of primary and secondary treatments as well as sludge handling. The primary treatment is designed to remove large solids (e.g. rags and debris) and smaller inorganic grit. Typical primary treatment operations include grit chambers and primary sedimentation tanks.
The secondary treatment removes organic contaminants by using microorganisms to consume biodegradable organics. Aerated lagoons, activated sludge, trickling filters and rotating biological contactors are examples of common secondary treatment operations.
In developed countries, these plants can have advanced treatment operations such as nitrification, de-nitrification and the physical-chemical treatment. Effluent is discharged to a receiving stream (creek, river, lake, estuary or ocean) post-treatment.
Both primary and secondary treatment processes generate sludge. Treated sludge can be used either as fertiliser/soil conditioner or disposed of in a landfill. Conventional pollutants are biochemical oxygen demand (BOD), total suspended solids (TSS), thermo-tolerant coliforms, pH, oil and grease.
Municipal wastewater treatment plants are not designed to treat toxic or non-conventional pollutants that are present in industrial wastewater. Effluents from both industrial and commercial sources can cause problems in municipal plants. It can also have detrimental effects on the water quality of the receiving stream.
That is why the pre-treatment of effluents is recommended. The objectives of pre-treatment are to prevent the introduction of pollutants into the municipal plant, which would otherwise interfere with its operation.
A closer look at CET plants reveals a number of potential problems. Assuming a CET plant is established in Karachi’s Site area, almost all industries in the industrial zone will discharge their effluent to that plant. Under normal practice, only similar types of industries should connect to the plant and discharge their pre-treated effluent. Some industries may have cosmetic pre-treatment while others may not have any pre-treatment at all. More importantly, heterogeneous types of effluent from different industries will likely discharge into the plant.
What will happen to the plant? Simply stated, it will not work. In biological terms, it will be “struck up”. There are two reasons for this. One, toxic substances like heavy metal, organochlorines, polychlorinated biphenyls and organic fatty or acetic acid, will find their way into the plant’s influent waste stream. If the CET plant consists of the aerobic system, those toxic substances will wipe out the bacterial population, which is otherwise responsible for the degradation of organic matter.
The CET plant will become non-functional if there is a high effluent load. Textile industries, typically, discharge high volumes of effluent load.
If the CET plant is of anaerobic (devoid of oxygen) type, an antagonism of biological reactions will take place. Acids will destroy the methane bacteria, making the plant biologically dysfunctional.
Sludge collected in the sedimentation tanks of the plant will be highly toxic. There is no way that can be treated. It will be dumped at some dumping site, causing groundwater and air pollution.
The industrial wastewater treatment entails many operating problems that generally require help from foreign qualified experts. A small technical error can easily upset the whole plant. The main problem with industrial wastewater is that it contains toxic pollutants, which cannot be easily removed.
If the municipal wastewater treatment can somehow remove toxic pollutants, they will end up in sludge. Toxic pollutants in sludge mean that the latter cannot be safely disposed of.
Toxic metals removed in the primary treatment stage can affect the efficiency of sludge digestion. For example, chromium can inhibit the reproduction of aerobic digestion microorganisms, thereby disrupting sludge treatment. It will produce sludge that must be disposed of through special treatment.
Industrial wastewater contains volatile organics, which produce gases. When discharged into the sewer system, gases accumulate in the soffit area (headspace of sewers) of the pipe. These gases can cause explosions. In Kentucky, United States, large quantities of hexane was discharged into the sewers in 1981. It got ignited and destroyed more than three miles of sewers and roadways, causing $20 million in damage.
A combination of different streams also causes problems. For example, cyanide and acid, both present in many electroplating operations, react to form a highly toxic hydrogen cyanide gas. Likewise, toxic gas hydrogen sulfide is formed in leather tanning operations.
Metals like cadmium, chromium, mercury and lead cannot be destroyed or broken down through treatment. Toxic metals can cause a number of human health problems, such as lead poisoning and cancer. Toxic organics, like pesticides, dioxins, solvents and polychlorinated biphenyls, are cancer-causing. They can cause kidney and liver damage, anaemia and heart failure.
Thus, it will not be possible for the industries in Karachi to maintain the sanctity of these plants. As a result, they will become biologically dysfunctional. The plants’ effluent will pollute the receiving stream. It will also bring a bad name to the Sindh industries department because it will be the sponsoring agency.
The best solution is to give the funds of Rs3bn, earmarked for the installation of five CET plants in Karachi’s industrial zones, to the respective trade and industry associations through the Karachi Chamber of Commerce and Industry (KCCI). The associations should establish the plants on their own. They should direct the industries to establish pre-treatment systems. The associations should then be responsible for the operation and maintenance of these plants.
More importantly, the associations should be made responsible for the effluent quality of the treatment plants, which should meet the effluent discharge standards. The Sindh industries department should act as the watchdog and should be at liberty to impose heavy fines on the associations in the case of non-compliance.
The writer is a former director of the Environmental Protection Agency, Sindh
Published in Dawn, The Business and Finance Weekly, November 18th, 2019