A Maynilad customer outside the sewered area may request for free septic tank cleaning once every five years. This program naturally gives Maynilad a huge volume of septage to treat. Septage or liquid-solid human waste is removed during the desludging of septic tanks.
A mobile dewatering unit (MDU) can separate the solids from the septage. The liquid removed after separation can be returned to the septic tank. This is the in situ method of septage treatment.
Meanwhile, some of the sludge can be brought to the treatment plant where it is processed to reduce moisture content. Both septage treatment options produce biosolids, which are solids removed from the sludge and are also called drained human waste.
There are 18,000 septic tanks to be desludged every year and the number is increasing. This generates 100,000 cubic meters of septage. In 2005, Maynilad produced 18,000 cubic meters of biosolids from its septage treatment plant and MDUs.
This led Maynilad to search for a new scheme for its sanitation program. "We wanted to maximize the organic potential of septage and biosolids, as well as meet the required environmental safeguards and regulations. At the same time, the scheme should be financially viable, sustainable and comparable in cost with traditional septage and treatment operations," said Francisco Arellano, Maynilad senior assistant vice president for environmental and quality management.
A tripartite collaboration among Maynilad, the Sugar Regulatory Administration (SRA) and the Farmer’s Cooperative of Pampanga was the answer.
An experiment facilitated by Maynilad and the SRA in 2004 showed that septage and biosolids, when combined with chemical fertilizer, actually enhanced soil nutrients and eventually led to better sugarcane yields. They provided the nitrogen requirement of the soil and improved its nutrient retention capacity.
"Septage can be used in watering the plants while biosolids can be mixed with farm residue such as bagasse, mudpress, mill ash, among others to be converted into organic fertilizer through composting," said Oscar T. Quilloy, Maynilad-SRA Cooperative Research Manager III and project leader.
The SRA identified the sugarcane farms in Pampanga as suitable areas for biosolids and septage application. Sugarcane farms in Pampanga and Tarlac recorded the lowest yields due to lahar or pyroclastic material ejected by Mount Pinatubo’s eruption in 1991.
Findings of the Maynilad-SRA study showed the following:
• Microbial populations in septage and biosolids are non-pathogenic to plants;
• Septage and biosolids contain substantial amounts of essential macro-nutrients which improve water absorption and soil fertility;
• Heavy metal content is within established standards;
• Incorporation of septage and biosolids during land preparation has remarkable influence on soil pH (acidity or alkalinity), total nitrogen, phosphorus, calcium, sodium and potassium;
• Application of septage and biosolids built up soil fertility indices after harvest;
• Sugar cane yield using septage was higher compared to biosolids; and supplemental nitrogen is not needed for 100 cubic meters per hectare septage application, which actually provided the highest economic return.
Quilloy stressed that the residual effect of organic fertilizer is an advantage since it prolongs the fertility of the soil, as opposed to inorganic fertilizer that entails an abrupt release of nutrients and more frequent application.
The use of septage and biosolids is also environment friendly. The waste disposal system being applied by Maynilad has already passed the safety standards set by the government.
Meanwhile, Maynilad is providing septage and biosolids to farmers for free, including mango farms for demonstration purposes. It applied for registration and was recently granted a temporary permit by the Fertilizers and Pesticide Authority to be a licensed "soil conditioner manufacturer." It is now delivering to 18 farms in Pampanga and the demand is expected to rise as more farmers learn about the economic and other advantages of organic fertilization.