PASIG RIVER,MNL:HOPE IN WATER QUALITY?

CURRENT WATER QUALITY INDICATOR SCORES FOR THE PASIG RIVER; MANILA, PHILIPPINES (partial report, to be continued)

By Freddie Butch Rances Rabelas Obligacion, PhD,MBA (Honors), MA, BS Psych (magna cum laude); Senior Consultant, PASIG RIVER REHABILITATION COMMISSION, Quezon City, Philippines; Elected member, International Scholars Honor Society of Phi Beta Delta (The Ohio State University at Columbus Chapter) and the Phi Kappa Phi International Honor Society (The Ohio State University at Columbus and the University of the Philippines at Diliman Chapters); Phi Sigma Biological Sciences International Honor Society and the Pi Gamma Mu International Social Scienes Honor Society (University of the Philippines at Diliman Chapter)

BIOLOGICAL/BIOCHEMICAL OXYGEN DEMAND (BOD)

BOD is the amount of dissolved oxygen needed by aerobic biological organisms (those requiring oxygen for their metabolism) in a body of water to break down organic material present in a given water sample.  Alternatively, it is defined as a measure of the oxygen utilized during organic matter degradation at a specific time and temperature. 

High BOD levels indicate a condition where there is a reduction of oxygen availability to the microbial population to degrade organic content in a particular water sample.

The DENR standard for Class C waters is a BOD level equal to or less than 7.0 milligrams per liter.  This criterion suggests that lower BOD values are signs of good water quality.

Compared with the DENR standard, all 8 esteros’ relatively high values exceeded the 7.0 upper limit which imply low oxygen availability (Appendix 1-B).  The lowest BOD reading was observed in Sunog Apog (32 mg/L), while the highest was in San Lazaro (121.67).

 DISSOLVED OXYGEN (DO)

DO refers to the amount of oxygen dissolved in a waterbody.  Because fish and other aquatic organisms cannot survive without oxygen, DO is considered one of the most important water quality parameters.

In nature, oxygen from the atmosphere can be mixed or diffused into a waterbody.  The mixing is easiest when waters are rough or where water is tumbling over rocks.  Oxygen is also introduced by green aquatic plants and algae during photosynthesis.  The higher the water temperature, atmospheric, and hydrostatic pressure, the lower the DO concentration.

Cold water holds more oxygen than warm water.  Illustratively, pure water at 4 degrees Celsius (40 degrees Fahrenheit) can hold 13.2 mg/L of dissolved oxygen at 100% saturation.  At 25 degrees Celsius (77 degrees Fahrenheit), pure water can hold a mere 8.4 mg/L.

It is helpful to know that the toxicity of toxicants such as lead, zinc, copper, cyanide, ammonia, hydrogen sulphide, and pentachlorophenol can double when DO is reduced from 10 to 5 mg/L.

Human-contributed factors that decrease DO include increased amounts of nutrients (e.g. phosphorus and nitrogen) from lawn/farm fertilizers, runoff from animal feeding, storm water, and human waste discharges.  These sources may contribute to increased growth of aquatic plants and algae.  As these organisms die and are decomposed or degraded by bacteria, oxygen is consumed by bacteria which, in turn, leads to a reduction in DO. 

Relatedly, in the process called eutrophication, the influx of organic material to the riverbottom (sedimentation) may cause hypoxia (the rapid depletion of oxygen), “dead zones”, and harmful algal blooms.

The DENR standard for Class C waters is a DO level equal to or greater than 5.0 mg/L.  Aquatic life is placed under stress when DO concentration falls below 5.0 mg/L.  If the DO is equal to or less than 2.0 mg/L, extensive fish kills may result.  On the other hand, good fishing waters require a DO of 9.0 mg/L or higher.

Viewed against the minimum 5.0 standard, all 8 esteros failed to meet this criterion with their relatively low values ranging from a low of 0.51 in Binondo to a high of only 1.47 in Magdalena.

DISSOLVED OXYGEN (PERCENTAGE OF SATURATION)

Do concentration may likewise be expressed as percent saturation or the amount of oxygen in a liter of water relative to the total amount of oxygen that water can hold at a specified temperature. 

The DENR standard for Class C waters is greater or equal to 60%.  In 2009, all 5 esteros with data did not make the grade, to wit: Maypajo with the highest percentage saturation among the five esteros (38.04%), Kabulusan (17.16%), Magdalena (15.23%), Sunog Apog (10.88%), and the lowest percentage saturation observed in Binondo (7.58%).  Data for Vitas, San Lazaro, and de la Reina were unavailable (Appendix 1-E).

TOTAL COLIFORM

Coliform is a very common rod-shaped bacterium. It is relatively harmless, not thought of as disease-causing to humans, and lives in large numbers in soils, plants, and intestines of warm-blooded (humans, mammals) and cold-blooded animals (snakes).  Coliform found in the gastrointestinal tract of humans aids in digestion of food.

Because pathogenic bacteria in wastes and polluted water are usually much lower in numbers and much harder to isolate and identify, the coliforms which are usually in high numbers in polluted waters are used to determine total coliform which is viewed as a general indicator of potential contamination of a water source with pathogenic and disease-causing organisms. 

However, it must be noted that many coliforms live in the soil and these organisms may be the source of that appear in water, particularly surface water.The DENR standard, Class C waters, is less than or equal to 5,000 MPN (Most Probable Number) per 100 milliliters of water.  All 8 esteros failed to meet this standard, as shown by counts way exceeding the maximum limit (Appendix 1-E). 

San Lazaro had the highest total coliform (13,300,000 MPN/100 ml. of water), hence the worst water quality.  Binondo showed the lowest count (2,160,000 MPN/100 ml. of water, thus the best water quality according to the total coliform criterion.

It is interesting to consider that the total coliform of all 8 esteros were considerably lower than the 2012 annual mean total coliform of the entire Pasig River which was 170,000,000 MPN/ 100 ml. water.

 TOTAL FECAL COLIFORM

Fecal coliforms are the coliform bacteria that originate specifically from the intestinal tract of warm-blooded animals (humans, racoons, beavers).  The fecal organisms themselves are not harmful but because they live in the same portion of the digestive system where disease-causing microorganisms occur, the presence of fecal bacteria in a water sample indicates that such sample might contain microorganisms harmful to human health.

Fecal coliform provides stronger evidence of fecal contamination than total coliform counts.  Fecal coliform could not be distinguished as human or animal.

E. coli is the indicator organism of choice for fecal contamination. However, there is another group of fecal coliform, the thermotolerant fecal coliform which are differentiated from total fecal coliform using elevated temperatures (43 to 44.5 degrees Celsius) during incubation.

Very high levels of fecal bacteria can give water a cloudy appearance, cause unpleasant odor, and increased biological/biochemical oxygen demand (BOD).  Sources of fecal bacteria in surface waters include outflow from wastewater, domestic and animal manure, on-site septic tank overflow and discharge, outflow from wastewater treatment plants, storm runoff, and direct fecal discharge into water bodies.

To obtain data on fecal loading of water bodies, the water sample is incubated for 24 hours and the number of bacterial colonies that are formed is counted.  This figure is expressed as CFU (colony-forming units), MPN (most probable number of organisms), or HPC (heterotrophic plate count) per 100 ml. of water.  Parenthetically, HPC consists of a broad array of bacteria including pathogens, nonpathogens, and opportunistic organisms. 

HPC is used to indicate the general biological condition of the water sample which could, in the case of drinking water, measure the insufficiency of the water treatment process or the recontamination of drinking water in the water distribution system.  HPC, thus, indicates the safety of the water for recreational, fishing, and industrial purposes.

It must be remembered that water for human consumption must contain no fecal contaminants.  However, water with no E. coli may contain pathogens which are more resistant to environmental conditions or treatment technologies such as protozoa and some enteroviruses which are chlorine-resistant.

Worldwide, there are varying standards for total fecal coliform.  The Philippine DENR standard for Class C waters is less than or equal to 200 MPN/100 ml. water.  The World Health Organization (2006) set 103-104 CFU/100 ml. water as the standard for water reused in aquaculture and agriculture.  For water used for recreation and industrial processes after treatment, the WHO specified 1,000 CFU/100 ml. water for total fecal coliform and 5,000 CFU/100 ml. water for total coliform.

In the U.S., regulatory standards for fecal coliform varies by state and several fecal bacteria indicators may be used.  For instance, in the North Dakota/Minnesota region, fecal coliform is used with a regulatory value of 200 CFU/100 ml. of water.  The intent of such regulation is protect people who use rivers for recreation, just like the case for Philippine Class C waters.  The DENR standard is identical with that of the North Dakota and Minnesota regions in the U.S.

 The scientific rationale for this upper limit is the idea that when fecal coliform counts exceed 200 CFU/100 ml water, there is a greater chance that disease-causing microorganisms are present.  American authorities advise that water contact be avoided at this fecal coliform level. 

 Possible diseases carried by waters whose fecal coliform counts exceed 200 CFU/100 ml. water include typhoid fever, dysentery, hepatitis, gastroenteritis, swimmers’ itch, and ear infectioA).

 The highest total fecal count, hence the worst water quality, was seen in Maypajo (7,040,000 MPN/100 ml. water).  The lowest, thus relatively the best water quality was in Binondo (4,800,000 MPN).

 TOTAL DISSOLVED SOLIDS (TDS)

 TDS is generally used as an aggregate indicator of the presence of a broad array of chemical contaminants such as point-source water pollution from domestic or industrial sewage, leaching of soil contaminants, and agricultural runoff.

 TDS is correlated with conductivity and is approximately 70% of the conductivity value (i.e. multiply the conductivity value by 0.70).  Many regions set a TDS maximum instead of establishing conductivity standards.  For sodium chloride (common salt) and bicarbonate, the specific factors are 0.49 and 0.91, respectively.

 The TDS levels--affected by wastewater and septic effluent, soil erosion, decaying plants and animals, urban/fertilizer runoff, and the area’s geological factors--are important to aquatic life.  For example, salmon, perch, and pike show reduced egg survival rates and hatching at TDS values above a range of 2,200 to 3,600 mg/L.  TDS is also critical to acquatic survival by keeping cell density balanced.  In waters with very high TDS, cells will shrink.  On the other hand, in distilled or de-ionized water, cells will swell because water flows into the cell as a result of extremely low TDS levels.

 High concentrations of TDS may cause adverse effects on water taste because they often indicate high alkalinity and hardness.  Alkalinity is a measure of water’s buffering capacity or the ability to resist changes in pH.  Excessive alkalinity is associated with excess dissolved solids and high pH values. 

 On the other hand, hardness is a property which makes water form an insoluble curd with soap due primarily to calcium and magnesium.  Very hard waters have no known adverse health effects and may, in fact, make water more palatable than soft water.

 Hardness is primarily of concern because it forms scale in broilers, water heaters, and cooking utensils.  Hardness also requires more soap for effective cleaning, causes yellowing of fabrics, and toughens vegetables cooked in water. The hardness value of good-quality water is less than or equal to 270 mg/L or 15.5 grains per gallon.  Waters softer than 3-50 mg/L may be corrosive to piping.

 The DENR standard for Classes A (sources of water requiring complete treatment to meet national standards for drinking water) and D (water for agriculture, livestock watering, and industrial water for cooling, among others) waters is less than or equal to 1,000 mg/L.

 In 2014, all 8 esteros met the DENR standard with their low values ranging from 0.49 in De la Reina to 15.12 in Sunog Apog (Appendix 1-B).

 TOTAL SUSPENDED SOLIDS (TSS)

 TSS measures the amount of undissolved solid particles in water such as silt, decaying plant and animal matter, domestic and industrial wastes. This measure is closely related to turbidity. As mentioned earlier, high TSS or the presence of dark-colored humic acids from decaying vegetation results in high turbidity.

 High TSS levels may be a result of sand and gravel quarrying, domestic and industrial wastewater, runoff from agricultural land, storm drains, and denuded forests among other sources.

 The DENR Class C waters standard is a relative criterion of less than or equal to or not more than 30 mg/L increase.  The Philippines does not have an absolute standard for TSS, unlike Australia and New Zealand, to name a few.

 In 2014, Maypajo, Binondo, and De la Reina met the DENR standard, while the five other esteros did not.  The worst water quality was noted in Magdalena and San Lazaro, using the TSS as a parameter.

(TO BE CONTINUED)