The connection between water supply and disease

Dirty, water

Could improving wastewater management be the next public health revolution in Costa Rica?

The relationship between humans and our water environment is becoming more strained than ever before. Not only does water make up our landscapes, it also moves both above ground and below. Through this movement, water contamination becomes concentrated. Whether it is sediment from excessive erosion or nutrients from crop production or even plastics and waste from flooding, water moves, dissolves and changes material. Our management of water storage, purification and use deserves much greater attention than it is currently given. By neglecting it, our problems will worsen, flooding damage will increase, and human health problems will be exacerbated.

In Costa Rica, water is found both above and below the surface. The soil is porous, allowing ample groundwater storage and flow, creating vast aquifers throughout the country. Surface water begins in mountainous regions forming river channels that move through the landscape quickly due to intensive slopes and thin watersheds. Precipitation is variable with heavy rains beginning in May and concluding in November. The dry season (beginning in December) produces a limited amount of rainfall until rain returns again in May. While rainfall patterns and groundwater abundance are understood, profound changes occurring to each now influence decisions and management more than any other period in the past.

Drinking water in this country of six million people, is almost exclusively derived from groundwater. Tapping aquifers from wells, springs or direct flow, this water is extracted, stored, tested, treated and distributed. Government control is strong with the central water authority (AyA) regulating drinking water in large metropolitan areas and delegating authority to local water boards (ASADAs) in rural areas. Water boards must adhere to strict testing and treatment standards to ensure quality drinking water. Residents pay a nominal fee for water supply and local ASADAs use all of these funds to ensure water production and testing. While supply from these aquifers is not well understood, reliance on them for drinking water supply and wastewater treatment is essential.

The cost of recharging aquifers

The first step of recharging aquifers is to quantify water distribution through precipitation patterns and water use. Demarcations between wet and dry seasons in the tropics are well established. While each season contains inherent variability, heavy rains distribute precipitation through May till December, with dry weather occupying the remaining months. While rainfall amounts are relatively consistent, rainfall intensity is changing.

Increasingly intense storms are more becoming more common, especially those that deluge the landscape with rainfall so intense that most of the water becomes runoff into stream channels. These storms alter the landscape, generate destructive flooding and do not adequately infiltrate into aquifers. Instead of mist and fog that regenerates cloud forests and slowly infiltrates, intensive rain deprives groundwater and vegetation of adequate recharge. Intense rainfall is erosive and transports sediment and pollution. It is hard to manage, and infrastructure is not built to handle intensive storms. Changing rainfall intensity patterns is a real threat to water supply and treatment.

Furthermore, dry seasons are becoming more and more pronounced. With the passing of the Central American Free Trade Agreement (CAFTA), many small agricultural farms cannot compete on the international stage. These operations are either purchased by multinational conglomerates or incorporated into larger operations to maximise both production and profits. The need for increased production has led to Concentrated Animal Feeding Operations (CAFO’s) replacing once smaller farming operations. Cash crops such as pineapple, coffee and bananas if produced in areas advantageous for international trade, but are water starved must therefore find more water to irrigate. The need to pipe water or directly divert rivers for agricultural operations is ongoing.

Crop agriculture and CAFO’s are highly polluting to streams and degrade water quality. Pesticides, nutrients and bacteria flow from land or concentrated lagoons impacting stream segments for long distances into communities. Wastewater is the other concern. Releases from urban areas plague many rivers throughout the region. Treatment facilities need to be built or upgraded to minimise the problem. Additionally, rural areas need an understanding of treatment effectiveness and a comprehensive study of the problem. Household straight pipes, septic system function, collective burden on groundwater resources and effective management systems must be evaluated and rectified to properly control this problem. Far too much wastewater is emptied into the environment without adequate understanding of its fate, and with changing patterns of precipitation and demand for water, community health and disease may be the manifestation of this problem.

Formulating the culmination of these water issues with disease is elusive. Environmentally speaking, direct measurement of pathogens is difficult. Pathogenic indicators, such as faecal coliform bacteria and E. coli, are organisms that are not disease causing but instead are correlated to the probability of disease. Simply expressed, increasing levels of indicator bacteria associate with increasing probabilities of disease. Scientific strength of this relationship is strong and well documented in the scientific literature. Moreover, E. coli remains the most consistent and reliable environmental indicator available for measure. This bacterium responds to multiple types of organic pollutants and helps identify pollution sources making it an ideal indicator species. Yet because it is present in water sources, and it always is at low levels, probabilities can be skewed.

Sediment – freshwaters biggest threat

Compounding this problem is sediment. Sediment entering water sources is considered the greatest threat to freshwater resources worldwide. It is filling reservoirs and putting dams at risk while reducing our capacity to store water for use. It is eroding off cropland reducing soil fertility and transporting animal waste directly to rivers. In addition to this, it also provides a perfect vehicle for the transportation of pollutants and bacteria. Depending on the type of sediment, nutrients such as phosphorus and bacteria adhere to sediment surfaces travelling great distances through water transport. These sediment surfaces provide the ideal colonisation area for bacteria creating biofilms allowing viability in the environment for extended periods of time.

Suspension of clay sediment is especially troublesome as bacteria readily adhere to its surface through electrical charge and due to small particulate size and shape this type of sediment remains in suspension for very long periods of time. Therefore, water that contains sediment can usually be assumed to be polluted with harmful bacteria. Control and minimisation of any land disturbing activity that creates exposed soil must be achieved to control this problem. Agricultural fields or other open areas allowing precipitation to directly contact the soil surface need protection along the edges of streams and rivers. Areas of tree buffer are the simplest and most meaningful management strategy for this problem.

To illustrate this problem, our research team measure E. coli concentrations from headwaters to coastal plain through three river systems along the pacific slope in northwest Costa Rica. What is striking is the influence of two important factors pertaining to bacterial abundance expressed by E. coli and human behaviour. In the upper reaches of these river systems and during the dry season, we only see elevated E. coli where there is extensive development and grey water release. Remaining areas are protected by forest corridors and bacterial contamination is low. As water flows down through each system, bacterial concentrations do elevate but are below the 200 cfu/100ml threshold for recreational use. This illustrates the problem of direct grey water and developmental release on receiving waters in such areas.

The wet season is much more striking. Only the most well protected areas remain below thresholds. The other areas become elevated or remain elevated in E. coli as rains drive pollutants into the river systems. Moving lower along the slope, the areas generally surrounded by agriculture, pasture and development increase with bacteria. This is concerning as lack of forest buffer allows direct runoff from open fields into stream channels. Also, direct release of grey water along with saturation of septic tank fields infiltrates nearby streams. These bacteria remain viable for extended periods of time and certainly have potential to create disease in communities when continually resuspended during subsequent storms.

The link between water quality and diseases in communities

First, a general concern over peptic ulcers, gastritis and stomach cancers in Costa Rica and Latin America is growing. In Costa Rica, incidences of gastric cancer are ninth worldwide and the second leading cause of cancer related death in the country. The central mountain regions contain 60% of the population with a significantly higher incidence of gastric cancer than similar coastal regions. Reasons for these problems are complex and multifaceted.

My research suggests community water quality problems directly translate into community health concerns. From my observations and work with many communities in Costa Rica, citizens consume a variety of untreated and treated drinking water from various sources. Wastewater disposal through septic systems and straight pipes directly into the environment is an unregulated and highly contaminating practice. My presumptive testing of aquifers demonstrates that untreated drinking water sources are contaminated with both total coliform bacteria and E. coli.

However, this poses the question of what the direct links between inadequate wastewater disposal and drinking water quality actually are. For example, what are the links between grey water direct discharge, unknown operational efficiency of septic systems and agricultural practices? As a result, how can we protect aquifers, rivers and freshwater resources? We are starting to find answers to these questions and generating solutions.

Firstly, there is strong literature evidence that chronic exposure to the bacterium Helicobacter pylori (H. pylori) in contaminated water leads to peptic ulcers and stomach cancer. Studies further suggest that H. pylori remains viable in water for extended periods of time allowing it to travel from contaminated sources such as grey water (water from kitchens and showers discharged directly into the environment) and septic tank effluent into water supply aquifers. Also, H. pylori may be more viable than other more conventional contaminates such as E. coli bacteria by growing on biofilms or other surfaces in the environment (and this certainly includes sediment). Furthermore, current evidence also suggests that water contaminated with E. coli, correlates well to similar contamination of H. pylori.

Measuring E. coli levels in water

We have developed laboratory facilities to measure levels of E. coli in water and correlate to areas of concern. Additionally, we are researching methodology to study H. pylori directly through correlation with other measurable environmental parameters. While this research will be correlative, we believe it will help to directly pinpoint sources and environmental viability.

Additionally, we are looking at ways to engage local communities to environmental health. Local Water Boards or ASADAs (as known by their Spanish acronym) are organised under the National Water and Sewer Authority or AyA (as known by their Spanish acronym). These local boards are responsible for providing treated drinking water to rural communities they serve. In their effort to provide clean drinking water, ASADAs currently exhaust all revenue available. They do not have any resources to monitor or control wastewater. Water fees are set by the National Authority (AyA) and cannot be increased by the local board. Continually, most Costa Rican residents believe water is a basic human right and should be provided free of charge. They also believe wastewater is a primary pollutant destroying biodiversity in a country that contains 5% of all biodiversity on this planet.

Clear connections between drinking water aquifers and wastewater treatment need to be mapped. Some of my research using river insect populations as indicators is promising. These insects respond to water quality and can be a barometer of health for a community. An index that is easily used by communities as a tool needs to be promoted. Finding ways to educate and then administer this index will empower local communities to better health and responsibility for water management. Grey water treatment systems are desperately needed. Biofiltration, raingardens and plantings directly at outfalls will treat this wastewater at the source. These efforts need to be implemented on a community level. Moreover, we are beginning a septic tank maintenance program looking at the extent of contamination and the ability of wastewater to travel through aquifers and into rivers and streams. Because aquifers are so important in providing potable drinking water throughout most of Costa Rica, the ability for these aquifers to also effectively treat septic effluent is imperative. Relationships among supply, flow, quality and treatment of water needs good quantification.

As these variables are studied and understood, we believe integration into the work of the ASADAs can accomplish adequate wastewater sanitation. Initially adding record keeping to current water customers is a first step. Knowing how each customer discharges grey water and functioning of their septic systems will provide the initial step. As we add additional water quality testing at points throughout communities, the collective impact of such practices will become clear. Human health will be added as an epidemiological study with practical solutions in various areas to follow. We see this research leading a needed reform in the management of biological corridors, watersheds and sanitation.


Dr Thomas Shahady

Assistant Professor of

Environmental Science

University of Lynchburg

+1 434 944 5684

Tweet @lynchburg

Please note, this article will appear in issue 32 of SciTech Europa Quarterly, which is available to read now.

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