MY PROJECT

Demonstration Environmental Sanitation Project at Monteverde, Costa Rica

By EcoEng Correspondent Stewart Dallas, Costa Rica

Info Monteverde Institute: http://www.mvinstitute.org

Development has proceeded in an ad-hoc fashion and local planning for the region has been virtually non-existent. Needless to say the associated environmental impact has been considerable. (‘Monteverde’ is generally used to describe the three communities of Monteverde, Cerro Plano and Santa Elena which are all adjacent to cloudforest vegetation on the Cordillera de Tilaran at an altitude of 1200-1600m).

Costa Rica has whole-heartedly embraced eco-tourism as a source of much-needed foreign exchange and until recently it was the nation’s number one industry in terms of financial turnover. While the country is famous for its enlightened approach to conservation and its sheer biological diversity, the impacts from unlimited ecotourism, population growth and a lack of any national master plan are being felt. In particular it is widely recognised that the pollution of water and water bodies, in hand with diminishing fresh water supplies, is now a real threat to the livelihood of all species, including Homo sapiens! (Of note: In Latin America 98% of all sewage is discharged completely untreated and this has resulted in high rates of disease and gross pollution, mainly as a result it has been argued, due to adherence to the principle of the water-based ‘flush and discharge’ technologies.

The two seasonal variations however both exacerbate and mask the true extent of the problem: in the dry season (Dec-April) it is common to see and smell greywater and septic overflow in the roadside drains and freshwater supplies are stretched; in the wet season (May-Nov) torrential daily downpours flush away and dilute the effluents and water supplies are abundant.

The reedbed is approximately 7.2m long, 1.8m wide and 0.6m deep and is a plastic-lined, subsurface-flow system based upon a design by Marshall. An internal plastic baffle wall extends the flow path to approximately 10m before water discharges to a shallow (0.2m) open pond (2.0m dia.). To reduce costs, gravel for the reedbed was largely replaced with cut up plastic (PET) drinking water bottles (I used a local non-recyclable brand) to provide an inert media and structural support for the plant roots. This plastic bottle layer was then topped with 15cm of crushed rock and the reedbed planted up.

Due to the region’s steep topography, wetlands - and hence native wetland plants - are non-existent, however several non-native reed species were located in a few isolated areas and were identified. The reedbed was planted with "Job’s Tears/Lagrima’s de San Pedro” (Coix lacryma-jobi), a member of the Tripsaceae family as the species considered to be the most suitable and yet non-invasive. Recent research however suggests that mixed resident vegetation may in fact prove to be more effective at nutrient stripping than monoculture systems such as this and some experimentation with this will be attempted.

After passing through the reedbed, the treated greywater flows into a shallow pond containing fish and some floating aquatic plants, before overflowing into a soakage basin planted with banana, two types of bamboo, sugarcane, taro and lemongrass.

At present the reedbed only receives greywater from two sinks within the Centre however a third sink as well as urine direct from the urine-diverting composting toilet will soon be connected. The main challenges to date have been: wet-season rainfall in terms of construction interference and excessive reedbed throughput due to the additional water volumes; and mosquito larvae populations in any standing water during construction (goldfish have been introduced to the pond for mosquito control).

While this arrangement does not simulate a typical domestic situation it will hopefully demonstrate an ‘in-principal’ environmentally-friendly local sanitation alternative (the Community Arts Centre will experience usage factors typical of a day-only public facility such as high urine and low fecal solids input). It will also provide experience with local plant species, soil and topography factors, climate, availability of materials, local social and cultural considerations before a perhaps more ambitious project for the area is undertaken.