Water quality - Wastewater treatment standards in different countries
In most developed countries, standards for wastewater treatment are continuously improving. Compared to the 1970s the effluent requirements for the most important pollutant indicators BOD, Nitrates and Phosphorus have steadily increased. For example, in the United states the clean water act from 1972 demands that all Municipal sewage treatment plants (POTW) are required to meet a weekly average BOD and TSS effluent value of 45mg/l or less.
Before 1972 2/3 of all wastewater was led untreated into natural water ways causing that some rivers – like the Cuyahoga River in Ohio – were so fouled that they caught on fire. Nowadays, the occurrence of micro-pollutants creates a new challenge for wastewater treatment in developed countries. Micro-pollutants originate from drugs, personal care products, pesticides and the anti-baby pill and enrich more and more in rivers and lakes. The UNESCO estimates that worldwide over 80% of wastewater is released to the environment without adequate treatment. Especially in third world countries less than 8% of all wastewater is treated before its released into natural waterways.
Some of the most polluted rivers in India show BOD levels between 200 and 500mg/l so for example the Markanda river in Northern India. As mentioned earlier, since the 1970s the minimum requirement in developed countries for BOD from municipal wastewater treatment plants is 45mg/l or less. When treated wastewater is released into natural waterways its further diluted so that rivers with a BOD below 8mg/l are classified as clean, below 20mg/l classified as borderline water and rivers with a BOD above 20mg/l are classified as polluted. Consequently, several water-related diseases, including cholera and schistosomiasis, remain widespread across many developing countries.
Although the costs of wastewater management are greatly outweighed by the benefits to human health, economic development and environmental sustainability many countries still don’t have sufficient wastewater regulations or governmental funding to improve the situation. Whereas in developed countries permits for BOD, nitrates and phosphorus are established for decades, most projects in third world countries focus on the improvement of BOD levels only.