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Waste Water Treatment using  Water Hyacinth Based Hydroponics

The lakes polluted with toxic chemicals are contaminating groundwater of Dhaka city, endangering the city’s most primary source of freshwater. "Groundwater contamination is an irreversible act that will deprive future generations of one of life's basic resources".

The civilization of Dhaka city that developed anchoring the vast reservoir of fresh water bodies – rivers and lakes, is rapidly disappearing and so will the age old City. Water bodies are required not only to supply potable water; they are also required to cleanse the city waste similar to the “Kidney” of a human body. High population density, rapid and unplanned urbanization and unrestrained industrialization, illegal land filling and encroachment of valuable water bodies in the city is accelerating the process to a premature death of Dhaka city. The water qualities of the lakes in the city, particularly in Gulshan, Baridhara, Banani and Uttara areas have such mind-boggling level of contamination, that they have been declared as “Endangered Water Bodies” by Water Supply Authorities. A study of WASA reported that the Tejgaon Washing and Dying Company alone toss out about 12,000 cubic liters of highly toxic chemical waste water into the lake.

The industrial and domestic drainage systems find an easy way out connecting to the lake, and dumps chemical, clinical, domestic sewerage and solid waste in the fresh lake water. Intense pollution has caused the demand for Biological and Chemical Demand of Oxygen as well as level of Dissolved Oxygen in lake water to drastically decline, making the lake impossible for any aquatic life to survive. In 2001 more than 20 tons of different species of fish and other aquatic life died providing a strong signal to all of us about the danger. Bacteria count in the water was found 1200/ml. According to the experts this water is not only unsafe for the aquatic life; it has reached such deadly point of contamination, that contact with the water can cause serious consequences.

The most critical and alarming condition of these water bodies in and around the city were identified recently, when it was learned that these water works actually as recharging areas, and contaminate the ground water reservoir. The toxic waters of the lakes are percolated into aquifers. The ground water reservoir which is the primary source of drinking water supply for the Dhaka city is now in severe threat.

According to the Water Supply Authority, Dhaka city is facing two most critical problems – 1) accelerated depletion of ground water reservoir, because majority of the water bodies and other sources of ground water recharge is being used up for fast urbanization, and 2) increasing trace of toxicity in the ground water, because the few remaining rechargeable sources that are left today are highly contaminated and are directly contaminating the primary source of potable water – the ground water. Every day the Water Supply Authority can supply only about 950 million liters of drinking water against a requirement of 1,400 million liters. This water supply primarily uses ground water. About 450 deep tube-wells in Dhaka are operated to meet the present demand for water. The present continuance high rate of extraction of ground water has already reached a depth of almost 70 meters, which has a danger of making majority of the pumps inoperative in next 4 to 5 years if the water table falls below 70 meters due to continuation of extraction at this rate. This accelerated rate of extraction of ground water is creating a separate threat – land subsidence. 2.73cm of land subsidence has already started to trigger in Uttara during the period between 1990 and 1999. The likelihood of land subsidence in the Gulshan-Baridhara-Banani and Motijheel areas is high because the ground water table in these areas has critically gone down.

The Clock is Ticking!
If we all do not act proactively today to safeguard the ground water reservoirs, the Mega Dhaka City will very soon face extreme crisis of not only supply of safe drinking water, but also potential destruction from land subsidence. We all must address the unplanned and illegal encroachment of water bodies in the city, stop improper dumping of sewerage and industrial waste in lakes, develop awareness on the critical role of the lakes, and take actions for enforcement of implementation of Environmental Laws to save the further deterioration of the situation. The consequences will be tremendously and it will affect all the dwellers of Dhaka city.

A Way to Solution
Considering the critical impacts of deterioration of water bodies in the city, ChangeMaker and WRDS have taken up initiative to treat the waste waters of the lakes in Dhaka city. The organizations have developed an extremely cost effective and biological method of water treatment through Water Hyacinth based Hydroponics, which has been proved successful in other countries, especially in China, Philippine, Myanmar, USA, India, Thailand, and Kenya. The scientists of NASA and other renowned research organization in various countries have proved the effectiveness of water hyacinth for waste water treatment. This project methodology was agreed by BUET and has been approved by the government to restore the water quality of the lakes. ChangeMaker and WRDS draws on the experience of hydroponics in Khulna, Gopalgonj, Syleht have taken initiative to restore water bodies in and around Dhaka, including Buriganga, to present its dwellers a pollution free, healthy environment.

Water Restoration Process
Water Hyacinth, with its extensive root systems and fibers, can take up chemical wastes from the water very fast and leave the water purified. These water hyacinths are even capable of absorbing heavy metals and reduce its concentration hundred folds. Water hyacinth can remove 99.9% fecal coliform bacteria from wastewater, and has the capability to decrease chemical oxygen demand (COD) of water by 83%-92%. The water hyacinths maintain the wastewater pH between 6.4-7.8 and the dissolved oxygen (DO) to a generally accepted standard of 5 mg/l

Gulshan, Baridhara, Banani lakes can easily be restored by using this Hydroponics technology. Scientific cultivation, regular harvesting and careful monitoring can effectively reduce algal bloom in water.

In Hydroponics or floating cultivation method aerobic composting of the hyacinths can be used to reduce emission of large amount of Methane gas. “Hydroponics” is even capable of trapping the green- house gases from being emited in the atmosphere. Byproducts of Hydroponics can be used to produce paper, furniture, bio-gas, compost fertilizer, and food for livestock.

What is Hydroponics (Floating Garden)?
Hydroponics is a soil-less cultivation system, which uses water surface for growing plants and does not involve direct use of natural earth. Literally hydroponics means, “Water Working” or “Water Activation”, refers to the fact that plants growing without soil are dependent on the supply of nutrient in water. Large hydroponics installations exist throughout the world for the growing of both flowers and vegetables. Hydroponics systems used by NASA’s Controlled Ecological Life Support Systems (CELSS) program at the Kennedy Space Center in Florida, USA, for cultivation of crops like wheat, soybeans, potatoes produced in a sealed, controlled-environment growth chamber, stimulating a food production module for space.

Hydroponics, as a farming system is not new in Bangladesh. People of the haor (wetlands) areas are accustomed to this system i.e. growing crops/vegetable on floating mats made from water hyacinth and various other semi-decomposed aquatic plants.
 

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