Will Diyawanna stink like Beira Lake in Colombo?

By Leenah Wahab  

Fish kills and algal bloom are among the many water quality problems facing Diyawanna Oya, a government official said yesterday.  

 Additional General Manager of Water Reclamation of the  National Water Supply and Drainage Board, Dhanesh Gunatilleke said the  lack of adequate sewerage infrastructure to convey and treat wastewater  poses serious ecological issues in Diyawanna. “If we don’t attend to it,  it will soon face the same fate as the Beira Lake due to organic matter  decomposition, creating of anaerobic conditions leading to odour  emanation and eutrophication, which reduces oxygen saturation in water,”  he said.  

A water quality assessment conducted in 2018 in Diyawanna  reported that dissolved oxygen concentrations were recorded as lower  than 2 mg/l in several locations. 

The Central Environment Authority  (CEA) regulation indirectly ensures that around 4 mg/l is maintained to  sustain aquatic species such as fish by permitting only to discharge  treated effluent of BOD (Biochemical Oxygen Demand) 30mg/l in to inland  surface water bodies, which have at least eight times minimum dilution  factor. For Diyawanna, the Water Board has proposed BOD less than 10 and  total phosphorus less than 1 mg/l, total nitrogen less than 2.5mg/l to  limit nutrient accumulation and to maintain ambient water quality,” he  said. 

 
Parliament has further reported instances of formation of  algae blooms, if not attended in a timely manner can cause odour issues  that prevail in Beira Lake rotten egg smell caused by Hydrogen Sulfide,  according to Gunatilleke.  

Mr. Gunatilleke said that the Ministry of Water Supply has  initiated an island-wide capacity-building programme to train Local  Authorities and their planning committee members on onsite wastewater  management, as over 90% of the country’s population rely on onsite  wastewater disposal systems. “We have covered training programmes in the  Jaffna Peninsula, Trincomalee, Polonnaruwa and Anuradhapura, but  sometimes lack of commitment and transferring of trained staff of Local  Authorities to different divisions, so the knowledge doesn’t stay within  the system and hardly ensures the sustainability of the systems,” he  said.  
In 2013, a factory in Rathupaswala suspected of improperly  releasing industrial wastewater into land, rendering drinking water in  12 surrounding villages acidic and unsafe for consumption. Following the  incident, Gunatilleke said the Water Supply collaborated with the CEA  to enhance knowledge on groundwater pollution through training  programmes, and prohibit the establishment of high-polluting industries  upstream of water intakes.

“Micropollutants are very difficult to remove  by conventional water treatment techniques as they cannot be broken  down by bacteria in upstream industrial wastewater treatment plants. We  cannot relocate these industries, only operate them in a more  sustainable manner. For example, interceptor pipelines with pumping  stations have been constructed to transport treated effluent from the Biyagama Export Processing Zone downstream of the proposed salinity barrier  at Kelani River protecting Ambatale and Biyagama water intakes, which  provides water to almost five million people including the floating  population,” he said.  

The National Water Supply and Drainage Board have further  implemented a 14,500m3/day wastewater disposal project in Kandy and  17,000m3/day wastewater disposal project in Moratuwa-Ratmalana.   

In addition, NWSDB has implemented sewerage systems in  Kurunegala, Katharagama, JaEla/Ekala, Hikkaduwa and manages the operation and  maintenance of sewerage systems at major housing schemes.   

Further, NWSDB operates wastewater treatment plants in  major Industrial Zones at Seethawaka, Biyagama and Koggala on behalf of  the Board of Investment, Sri Lanka.   

Gunatilleke stated that necessary measures have been taken  to establish guidelines for minimising hazardous wastewater discharges  to the environment through industries, hospitals, laboratories and  beauty care centres under the ADB’s Knowledge Support Technical  Assistance (KSTA).  

When asked whether initiatives had been taken to recycle  wastewater for industrial purposes, Gunatilleke said, “Now industries  have the option for obtaining treated effluent (reclaimed water) from  NWSDB treatment plants at 1/3rd of the commercial rate for non-potable  uses. Currently, we are carrying out a survey involving industries  assessing the demand for use of reclaimed water for industrial  activities.” In addition, NWSDB obtained Environmental Impact Assessment  (EIA) from CEA approval to use treated effluent of proposed Jaffna  wastewater treatment for agriculture reuse, but the implementation was  held up due to the prevailing financial situation in the country.  

Gunatilleke further mentioned that the Water Board is  assisting hospitals, prisons and government institutions in designing, and rehabilitation their wastewater disposal systems and providing  technical and operational know-how for sustainable managing the said  systems. “Our aim is to improve the life expectancy of the population by  giving them safe, drinkable water.”