Manila Water Company: Wastewater

Wastewater

Minding What You Flush and Forget

Metro Manila Wastewater that conveniently drains out of our toilets, baths and kitchen do not truly disappear. Untreated wastewater eventually winds up into rivers, streams and groundwater and pollutes them. While the average Filipino households are very much aware of the importance of water for drinking, cleaning, etc., many have yet to be educated of the negative impacts of untreated wastewater.
Current government monitoring indicates that just over a third of the country's river systems remain as viable source of public water supply. In Metro Manila, all major river systems are biologically dead with dissolved oxygen plummeting to zero for most parts of the year. Moreover, studies show coli form bacteria contaminates up to 58 percent of groundwater sampled. As a result, water-borne sources caused approximately 31 percent of illnesses monitored for a five-year period. Untreated wastewater makes water unfit for drinking and recreational use, threatens biodiversity, and deteriorates overall quality of life.

Mandate and Projects

It is Manila Water's mandate, as Concessionaire to the Metropolitan Waterworks and Sewerage System (MWSS), to provide wastewater services that include sewerage and sanitation. Sewerage service includes the operation and maintenance of networks of sewer pipes and the Sewage Treatment Plant that treat the wastewater before disposal into water bodies. Sanitation service includes the operation and maintenance of vacuum trucks that clean household septic tanks and disposing the collected septage through environment-safe means.

From 2001 to 2005, Manila Water implemented the Manila Second Sewerage Project (MSSP), a World Bank-assisted project that aimed to improve wastewater service in Metro Manila. More than P1 billion was invested in programs to meet the sewerage and sanitation needs of Manila Water's customers and help reduce pollution to water bodies. Twenty-seven new STPs were constructed along with the rehabilitation older plants including the Magallanes STP, which at 40 million liter per day capacity is the biggest in the country. More than 20 newly -procured desludging trucks will improve sanitation service.

Immediately following MSSP, Manila Water started in 2005 the Manila Third Sewerage Project (MTSP) that aims to follow-up the accomplishments of it predecessor. This grand wastewater project is an $85 million initiative for the improvement of sewerage and sanitation conditions in the east concession zone. Aided by a $64 million loan from the World Bank, it will comprise the building of combined sewage-drainage systems, undertake a modernized, large-scale septic tank desludging program and education campaign to increase awareness on the negative effects of wastewater and its management.

Under MTSP, sewer coverage is expected to rise to 30% while number of desludging trucks will be expanded to more than 100. To manage expected rise in hauled septage, 2 septage treatment plants are currently being erected under MTSP.

Sewerage Program

Sewerage Program In many respects, sanitation and wastewater present even greater challenges than supplying clean, safe tap water. By 1997, less that 7% of the Manila Water concession area is connected to a sewerage system. Due to space constraints and the sheer cost of needed wastewater infrastructure, it would be near impossible to build centralized sewer networks in Metro Manila.

Innovative and unconventional solutions were needed to address sewage and sanitation needs of Manila Water's concession area. Some methods of tackling the issue include transforming communal septic tanks into compact or "package" sewage treatment plants where feasible.

Communal septic tanks are large units that service multiple dwellings. Due to their size, the communal septic tanks are a challenge to clean and service. To remedy this, Manila Water has worked to transform the septic tanks into mini-STPs. The communal septic tanks were outfitted with equipment for primary and secondary treatment to clean in-coming wastewater before releasing it to rivers and streams. Manila Water has successfully implemented this package approach through the World Bank funded Manila Second Sewerage Project (MSSP) and constructed 26 new package STPs (link to map). As a result, since take-over, we have doubled our sewage treatment capacity which now benefits more than half a million people.

Sanitation Program

Sanitation Program The rest of Manila Water's concession not connected to a sewerage system disposes its wastewater into septic tanks. Because septic tanks provide only primary treatment, they eventually leak out pollution into the groundwater or into the drainage system, which eventually finds its way in rivers. To address this, Manila Water currently operates a fleet of 20 trucks and performs regular, scheduled septic tank cleaning services for its customers free of charge. Manila Water also provides emergency services to customers for a fee.

But having the trucks empty septic tanks is only one part of the picture. What sets Manila Water apart from other septic tank cleaning contractors is that we dispose septage in environmentally acceptable means. We use combined strategies of septage-dewatering and enzyme bio-augmentation for sewage-septage co-treatment, and controlled disposal in lahar-laden areas.

The sludges or biosolids that results from the treatment of septage and sewage are also viable soil conditioners and Manila Water received a license from the Sugar Regulatory Agency to package biosolids as so.

Wastewater Process

click to enlarge diagram

Typical Wastewater Treatment Plant Process: (Activated Sludge)

Most wastewater treatment plants now use a variation of the activated sludge process to treat wastewater. In activated sludge, waste components in the water are "eaten" by a mixture of microorganisms mimicking the natural treatment method of rivers and streams.

1. Preliminary treatment:

Mechanical screens remove large particles, floating debris, sand and grit from the wastewater.

2. Primary treatment:

Large sediments settle as they slowly move along primary sedimentation tanks. The settled sediments or sludges are then pumped into digesters where they are processed anaerobically (without oxygen) until it is ready for disposal.

3. Secondary Treatment:

Wastewater flows across a tank equipped with aerators and blowers. The aerators supply oxygen that microorganism need to "eat" the waste components in water. The mixture of microorganism and remaining solids form clumps called flocs that settle in another sedimentation process. Some of this settled sludge returns to the aeration tanks while the rest are pumped into digesters.

4. Disinfection:

The harmfull microorganism are destroyed usually by chlorination.

5. Sludge Digestion:

Excess sludge are stabilized in digestion tanks, usually for 20 days, before being disposed.

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