Thorne Abbott

Constructed Wetlands

Fall 2000

Constructed Wetlands in Southeast Asia

 

One need not travel far within Southeast Asia before the weight of abject poverty is striking. Humanity is cheap: dysentery, disease and hardship run like the hot and cold spigots of Americans in the opulent $500,000 two-bath, four-bedroom homes. For all our wealth, there is an equivalently exponential relationship of hardship among the majority of Southeast Asians. The impoverished many, suffering diseases that are unthinkable to the rich western few. In the Philippines alone, the leading cause of death for children under five years of age is dehydrating diarrhea; a discomfort for us that is readily solved with tablets or pills. So how can we affect this dearth of human suffering? This paper illustrates a low tech, low cost, environmentally sound, alternative for treating wastewater, thereby improving public health and enhancing quality of life.

Without question, when one wanders through village and footpath, the two leading environmental problems in Southeast Asia are solid waste handling and water pollution. Trash is virtually everywhere. Landfills are rare and waste collection services are scarce. Plastic is the product of the new economy. Plastic is found everywhere. Back in the 1950's, the American roadside was littered with the substance of capitalism. Styrofoam McDonald's sandwich containers littered our highways and byways, and paper products, cigarette butts, oil containers were easily disposed of by opening the car door or rolling down the car window. With affluence came awareness, with awareness came education, with education came social change, and with social change came a different type of behavior. Perhaps education and affluence will change behavior in Southeast Asia. Even though impoverished, the private bungalow floors are tidy and clean. It is the commons, the roadside and footpath that are cluttered with solid waste.

Water pollution is more insidious. Diseases such as typhoid, cholera, and entero-viruses do not lie by the roadside to be swept up by the next generation. Water pollution comes in three forms in Southeast Asia; contamination of drinking water, polluted runoff, and wastewater discharges.

Drinking water comes from springs, rivers, and wells. In almost all cases, it is boiled before use. Boiling requires hear from oil, propane, gas, coal, or wood. All contributors too global warming, air pollution, and requisite money to purchase (petroleum products) or time for collection (wood). This in turn creates a reliance on money (capitalism) or a significant investment of time that could be spent on other activities.

Water for cooking, cleaning, showering, bathing, and laundry doesn't require boiling. Sub-standard water is acceptable for these activities. Yet cooking and bathing water, if not boiled, gives rise too potentially harmful waterborne diseases, infectious agents, and parasites such as tapeworms. If boiling occurs during cooking activities, the potential for disease is reduced, leaving only skin contact during bathing and doing laundry as 'at-risk' activities. This risk is nominal if drawing on well or spring water. But the risk is increased if drawing on river water, particularly in densely populated areas.

Springs may be used onsite, or may use a conveyance system. Pipes cost money whereas Bamboo may serve as a novel, low cost, shorter-lived conveyance system. However, springs are not as universally located geographically as wells within the region. Ground water wells require pumps and pipes which cost even more money than the conveyance of spring water. Of course, there is the use of human conveyance, a tradition dating back at least a millenium. Buckets serve well, conveyed two at a time on the shoulders of women or children. But this requires a disproportionate investment of time and energy for the poor.

Finally, there is the river. It comes, it goes, and it is a public good. Your waste becomes my bath water. My toilet becomes your water supply, if you are unfortunate enough to live downstream. Channeled from its mountain origins, stream water feed rice paddies, serves countless homes, and offers bathing holes and cool respites for countless numbers of tired workers at the end of the long hot day. And all these uses are provided before it reaches the urban corridors, where the rivers assimilative capacities are taxed beyond its corporeality.

To contrast, the city of Pittsburgh, PA is located at the confluence of the Allegheny, Monongaheala, and Ohio rivers in the Eastern United States. On average, the Monongaheala River goes through 27 homes before it reaches Pittsburgh, Pennsylvania (Borneman, 1997). From there, the Ohio River serves many dozens, if not hundreds of homes before it reaching the Gulf of Mexico in Louisiana. How much more burden is placed on Asiatic river-flows would be a mere guess, but certainly it must be greater than the America's.

In the United States, Publicly Owned Treatment Works (POTW) are located at every major urban discharge point along the river's path. These POTW's are monitored for effluent discharge quantity and quality on a regular ongoing basis to protect public health. In addition, water drawn from the river to serve communities and households goes through significant treatment either from in-home filtration systems or via the local drinking water authority (DWA). Just call the "Culligan" man to confirm the validity of in-home well, spring, and stream treatment processes. Since the inception of the Clean Water Act of 1972, America has invested over $67 billion in wastewater treatment infrastructure (Turner, 1998). In contrast, 85% of Asia's infrastructure has yet to be built. Asia's infrastructure needs represents 75% of the world's new construction opportunities, totally $6 trillion over the next 20 years (Gourlay, 1997).

For example in the Philippines, only 9% of Metro Manila's 11 million population is currently served by wastewater facilities. Of the estimated $175 million in new construction required, 39% will be imported from the United States, and as much as 90% of pollution control equipment will be imported from overseas (Madrazo, 1997). Although several local vendors provide services and equipment, quality control is sub-standard and inadequate to support pressing drinking water and wastewater infrastructure needs. Moreover, funding for the development of water quality services is unreliable. In Manila alone, lost revenue from leakage and illegal connections comprises 58% of the total drinking water delivered by the Metropolitan Waterworks and Sewerage System (ibid.).

This brings us to the core issue of wastewater treatment. In the United States, two options exist for residential homes; a centralized system or a decentralized system. Centralized systems typically consist of large pipes collecting a series of individual homes' wastewater. The large diameter pipes are usually buried under or next too the street or other public right of ways. The pipes convey sink, shower, bathing, toilet, kitchen, and laundry wastewater to a central municipal wastewater facility for treatment and discharge.

In contrast, decentralized systems typically consist of smaller diameter pipes that convey wastewater to a baffled underground unit (re: septic tank). Here, solids settle by gravity and are digested by anaerobic bacteria in the low oxygen environment. The decanted water flows by gravity from the septic tank to a drain field. The drain field has highly permeable soils, or soils amended with sand (sand mound) or other materials to promote infiltration. Smaller perforated pipes laid in a branching fashion allow for equitable distribution of the treated effluent. The effluent disperses through the drain field and percolates down through the soil, eventually reaching the water table or ground water. The underground and buried nature of wastewater treatment systems leads to an out of sight, out of mind perception regarding effluent disposal.

Southeast Asians are not terribly different. No one wants to drink, swim, or bathe in wastewater. Commonly, a home in Southeast Asia will rely on a septic system. The difference being that septic systems are used even in highly urbanized areas, in contrast to American centralized systems. One must also consider the social perspective. Houses are expensive to build or own and family units are more significant in Asia than in the U.S. Family dispersal is also much less frequent in Asia than in the West. Consequently, many families live in compounds. A compound may consist of several homes housing several related families or their members. Grandma and grandson are often only a door or two away.

The compound relies on a two-chamber septic system, or a one-chamber septic and a separately located one-chamber infiltration basin. Both basins consist of a 2-meter deep hole with earthen or concrete walls. The bottom is comprised of loose soil, sometimes amended with sand to enhance percolation into the ground. In most cases, neither basin has a sealed bottom, thus permitting effluent to be discharged by percolation into the ground.

Kitchen, bath (showers are not traditional, and thus uncommon), laundry, and sink gray-water is conveyed to the infiltration basin or second chamber of a two-chamber system. In contrast, toilet water is conveyed to an individual chamber or the first chamber of a two-chamber system. Toilets consist of a water closet or ceramic squat chamber. Discharges are conveyed by ladles of water drawn from a large basin situated within the bathroom. It should also be noted that the toilet effluent is of significantly higher strength than would be found in American systems due to minimal dilution.

In some cases, the kitchen and the toilet are located at the different ends of the compound, and thus have separate treatment basins. However, due to labor and material costs, the gray-water and the toilet discharge chamber systems are frequently built and located together. The toilet discharge is directed to one-chamber and the gray-water is directed to the second chamber of the two-chamber septic system. No conveyance or transfer of water occurs between the two chambers, presuming that the walls are concrete rather than earthen.

Such a two-chamber system makes good sense. One chamber handles high water loads, whereas the other chamber handles a high solids load. In contrast to Western style septic systems, there is no drain field for effluent discharge in Southeast Asian systems. In part, this is influenced by the cost of materials and labor for digging a drain field. However, it is more commonly the result of tight space requirements in crowded urban areas and family compounds.

The problem with such a system may be the lack of anaerobic bacterial action and proximity to groundwater supplies. This is particularly true of family compounds reliant on a well within the compound for drinking water. Because yeast it is not a commonly used material, it is rarely added too aid anaerobic action and solids digestion. Furthermore, only the semi-affluent middle class can afford the $112 in labor and material for a two-chamber [concrete-walled] septic system and ceramic water closet. The ceramic water closet being a disproportionate amount of the cost of such a system.

Having considered the aforementioned, one is faced with an interesting challenge:

I hypothesize that small treatment gardens may offer promise, and even hope for the rural poor in Southeast Asia.

One example of the application of this technology is the Sacred Mountain Resort in Bali, Indonesia. Sacred Mountain Resort is an eco-friendly resort catering to spiritually inspired Europeans. Activities at the resort center on Yoga and other forms of meditation and relaxation. Located in the town of Sideman, the resort is one of only two western facilities imposed upon a landscape of terraced rice fields and lush volcanic hillsides (Figure 1 & 2). Sideman is the center of one of Bali's oldest and most revered Hindu Kingdoms. The countryside is dotted with temples and shrines where local people come to lay offerings and give prayers daily. Each year, numerous Balinese come to Sideman to make the pilgrimage up Mount Agung's steep sides and gain enlightenment in reaching its summit. Many streams emulate from high upon the mountain care of numerous springs and seeps. They come together to form the Unda River which cascades down the hillsides and through the valley to form a valuable resource both spiritually and agriculturally (Figure 3). The cool fresh water serves as a source of invigoration, drinking water, irrigation for the many rice fields, and waste assimilation for the areas residents.

The Sacred Mountain Resort lies within 50 meters of the Unda River. The resort has two dozen bungalows and can house as many as 100 guests at any one time. Meeting halls, a small conference center, a restaurant, bar, and food services are available on the premises. In addition, the resort has 8 private 'plunge pools' associated with individual bungalows, a hot tub, and an Olympic sized in-ground swimming pool. During its development, local authorities expressed concern over the impact the resort would have on the neighboring community and its river resources. Authorities were concerned both with the aesthetics of the development, and the amount of pollution that might be created. To allay these concerns, the resort was built entirely with local sustainable materials (bamboo and grass) using local labor and traditional methods of construction (corded structure framing rather than nailed). The resort also instigated a full recycling program to minimize solid waste, as well as a composting program for food and other organic wastes. Indigenous plants were used throughout the resort for landscaping and beautification, and produce is grown either on-site or purchased from local growers. Due to high annual rainfall, a storm water treatment system was designed to handle rain events, as well as overflow and discharges from the various pools. Finally, all wastewater from the bungalows and kitchen area are treated on-site by a series of wastewater gardens. Developed by Mark Nelson of the Planetary Coral Reef Foundation, the gardens have been effective in reducing BOD, TSS, TN, TP, and fecal coliform bacteria while virtually eliminating any discharge to the neighboring river (Wouters, 2000).

Within the resort compound, bungalows are clustered together sharing a common rear courtyard. The courtyard is fringed by tall, thick natural tropical vegetation to reduce noise between bungalows, minimize the ability to see between neighboring bungalows, and to deter entry by the bungalows inhabitants. Due to the spectacular mountain or river views from each bungalow, the absence of access to the rear courtyard presents little loss to the guest's experience. From the second story of each bungalow, the rear courtyard presents the onlooker with an attractively landscaped garden full of flowers and lush green vegetation. The courtyard wastewater garden serves up to four bungalows or a combined total of 16 guests and is completely fed by gravity flow with no moving parts (Waymann, 2000).

For each bungalow, wastewater is derived from the water closet (eastern style toilet), sink, and shower. A centralized conventional septic tank captures the effluent from all the bungalows within the cluster. The septic tank provides primary anaerobic treatment and is completely buried except for an access port. Effluent flows from the septic tank into the first of three consecutive cells in the wastewater garden. Each cell consists of a 2 meter deep, rectangular cell lined with concrete. The concrete is sealed to prevent accidental seepage into groundwater supplies. Effluent moves from cell to cell by gravity through small diameter PVC pipes that are buried at least 7 cm below surface to eliminate odors and prevent accidental human contact. The bottom two-thirds of the cell is filled with limestone gravel. The limestone gravel interacts chemically with the effluent to enhance the removal of phosphorous (PCRF, 2000). A layer of mulch is placed over the gravel and native emergent vegetation is planted within the cell. The emergent plants promote oxidation of the effluent and decompose solids through aerobic and anaerobic processes in the root zone. The plant uses residual organic material to create biomass in the form of stems, leaves, roots, flowers, and fruit. In essence, the plants serve as aerators; pumping oxygen into the effluent through their roots, and decomposers; by absorbing nutrients and organic material into their tissues.

The sides of each treatment cell rise 20-30 cm above the neighboring courtyard ground level. However, the surface of the treatment garden is slightly lower to minimize entry. In addition, sharp stones are cemented at upright angles on the sides of the treatment cells to deter entry by un-winged animals or humans. The first two of the three-cell system behave similarly to a subsurface flow constructed wetland. The third cell acts as a wet well, offering access for monitoring water quality. The third cell is much smaller than the first two and consists only of a covered and lined concrete basin. A small outlet near the top of the cell (about 20 cm below surface) allows effluent to flow into a small sand mound where it percolates into the soil.

Water quality monitoring conducted for similarly sized wastewater gardens designed by Nelson show excellent treatment results (PCRF, 2000). Sampling conducted during 1997 and 1998 show significant reductions in Phosphorus, Nitrogen, BOD, and fecal coliform. Total Phosphorus was reduced by about 1/3rd in the septic, 1/3rd in the first treatment cell, and moderately in the second treatment cell (Figure 4). Overall, Phosphorus was reduced by an average of 87.8% to a 0.86 mg/l on average (Table 1). Total Nitrogen reflected similar reductions within the treatment train with an overall average reduction of 86.2% to 7.8 mg/l. Levels of BOD dropped significantly in the septic system, with additional consecutive reductions in the wastewater garden treatment cells. On average, BOD was reduced by 86% to an average discharge of 12.6 mg/l. In contrast, TSS was reduced by only 28.9% to an average discharge of 23.6 mg/l. Finally, fecal coliform was reduced by 99.9 % by the wastewater garden treatment system. Although these discharge levels are higher than drinking water standards, they meet or exceed U.S. government standards for irrigation water.

Table 1

US Gov't Std.

Discharge

Reduction

Total Phosphorus

1 mg/l

0.86 mg/l

87.8 %

Total Nitrogen

10 mg/l

7.8 mg/l

86.2 %

BOD

30 mg/l

12.6 mg/l

86.0 %

TSS

30 mg/l

23.6 mg/l

28.9 %

Coliform

~~~~~~

< 100 E+3 MPN/ml

99.9 %

PCRF, 2000

The wastewater gardens treatment system at Sacred Mountain Resort has been operational for at least four years. The gardens appear to be effective in removing TP, TN, BOD, TSS, and fecal coliform. To date there has been no accumulation of effluent in the third cell, which serves as a monitoring wet well (Waymann, 2000). Given the resorts high elevation and location very near the equator, it would not be surprising that evapo-transpiration rates would be extremely high. Nelson, reports that over 50% of the gardens effluent is lost to evaporation and transpiration at similar designed facilities located in Mexico (PCRF, 2000). Thus, it is reasonable to believe that the wastewater gardens are achieving the desired treatment effect. Of the four gardens viewed at the resort during a site visit in November 2000, three are illustrated below.

A large garden measuring 2 m X 6 m serves 10 bungalows (Figure 5). The system has an inline septic tank for primary treatment, two consecutive treatment cells, and a third small monitoring well. The two consecutive treatment cells have predominantly Ginger and Onje plants. Ginger has long flat leaves topped with white pleasant smelling flowers and is locally called Ruimput. Onje is a local grass species that grows to 2 m high and its stem is used as a traditional eye medication. The garden also had several brightly colored Birds of Paradise plants, one Palm tree (un-planted), and a number of low lying ferns.

Another smaller wastewater garden serves a cluster of 9 bungalows (Figure 6). The garden measures 2.5 m X 4 m and was interspersed with Onje, Ginger, and Dagdag Hias. Dagdag has two-tone leaves with white veins. It grows to 2.5 m high and has a singular thick stock with a large tassel-like flower at its top. The flower provides a large surface area for evapo-transpiration as evidenced by numerous droplets along its length.

A separate wastewater garden serves the kitchen and restaurant area (Figure 7, 8, 9). A large grease trap (3m X 3m X 2m) captures wastewater prior to entering the garden. During the first two years of operation the garden became clogged and backups of the system occurred frequently (Waymann, 2000). The gardens vegetation and gravel was removed, the conveyance system cleaned, and new gravel and vegetation was planted (ibid.). As a consequence of high grease loads and complex fats, it is apparent that the clogging would continue without some form of chemical conditioner. A biologically based microbial enhancement product has been found to be effective at reducing oil and grease to treatable levels. The product, BioSolve (distributed by BioSystems LTD, Australia) is added at a rate of one liter per day to the first chamber of the kitchens grease trap (Figure 10). Since the inception of its use, there have been no further backups of the wastewater garden treatment system. Unlike the aforementioned gardens, the kitchen treatment garden is substantially more biodiverse. Species include Palm, Banana, Rubber, Bird of Paradise, Ginger, Onje, and at least four other species not identified (Figure 11 & 12). The garden is also three to four times larger than the gardens serving the bungalows. The larger size is justified given the frequency and intensity of use, as well as the higher solids, oils, and grease loads placed on the system.

In addition to the contained wastewater gardens, a series of storm water treatment methods were employed throughout the resort. Rain water, runoff, and pool overflow is directed through a denderic pattern of culverts and channels (Figure 13, 14) to grass biofiltation swales, retention and wet ponds, infiltration basins, and a pocket wetland. The velocity of these flows is slowed along the way by natural rock weirs and gabion's, which create cascades, waterfalls, and seeps while capturing larger solids (Figure 15, 16, 17). A pocket wetland and a wet pond contain emergent and submerged vegetation including Lotus flowers, which are used in table settings at the restaurant (Figure 18). Other local emergent vegetation is used to create an attractive landscape that forms a variety of heterogeneous designs and percolation gardens. In many instances, trails and elevated paths follow (or guide) the storm water to the various treatment areas. To the untrained eye, the storm water treatment train appears as a series of paths winding through beautiful gardens that fringing pools and border small rivulets of chattering water (Figure 19). Remaining storm water or run off is collected in a natural micro-pool, with a level adjustment composed simply of a block of wood between two well hewn rocks (Figure 20). The significantly cleansed water is discharged through a grass swale channel to an adjacent landowners rice paddy where harvested rice is eventually sold to the resort for food (Figure 21).

In conclusion, Sacred Mountain Resort exemplifies how thoughtful planning and designing with nature can take perceived 'waste products' and turn them into a useful, viable resource that is both healthful and aesthetically pleasing (Figure 22). The application of constructed wetlands in a scientifically credible, environmentally sound manner can be a useful alternative for resorts, communities, and family compounds concerned with improving public health and conserving their valuable natural resources. Constructed wetlands and wastewater treatment gardens similar to those described herein offer an opportunity to provide sustainable development for those in greatest need. A few simple changes may be all that is required.

 

 

Citations

 

Borneman, David

Director

ALCOSAN Public Utilities, Pittsburgh, PA.

Personal transmission October 20, 1997.

Gourlay, Peter

"What and Where are the Opportunities?"

CNA / Schinner

WEFTEC 97, Workshop #112, Infrastructure Needs Equal Business Opportunities in Asia

Water Environment Federation, Alexandria, VA 22014. October 18, 1997.

Madrazo, Alma

Philippine Water and Wastewater Market Opportunities

US-AEP Philippines

WEFTEC 97, Workshop #112, Infrastructure Needs Equal Business Opportunities in Asia

Water Environment Federation, Alexandria, VA 22014. October 18, 1997.

PCRF

Wastewater Gardens TM.

Mark Nelson, Vice President of Waste Recycling Systems

Planetary Coral Reef Foundation, Sante Fe, NM.

http://pcrf.org/wwg.htm

http://www.pcrf.org November, 2000.

Turner, Billy

"Clean Water Act: 25 years later"

Director, Columbus Water Works, Columbus, GA

Conference on Urban Water Quality, Quebec City. February 1998.

Waymann, Nama

Former Manager

Scared Mountain Resort

Personal transmissions, October 27 - November 1, 2000.

Wouters, Walter

Resort Consultant

Sacred Mountain Resort

Personal transmission, November 1, 2000.

Figure 4 Performance Data

Figure 1 Sacred Mountain Resort

 

Figure 2 Sideman, Bali, Indonesia

 

Figure 3 Unda River

Figure 5 Wastewater Garden (10-12 Bungalow)

Figure 6 Wastewater garden edge

Figure 10 BioSolve

Figure 7 Wastewater Garden (Kitchen)

 

Figure 8 Species diversity within garden (Kitchen WG)

Figure 9 Garden surface with pea gravel (Kitchen WG)

Figure 11 Plant diversity & beauty

Figure 12 Lotus flowers in pocket wetland

Figure 13 Pervious path with channels

Figure 14 Storm water channel

Figure 15 Storm water rock cascade

Figure 16 Storm water seep

Figure 17 Pocket wetland

Figure 18 Retention pond

Figure 19 Storm water channel & percolation garden

Figure 20 Simple wood weir

Figure 21 Final storm water discharge channel

Figure 22 Sustainable design with Nature