By Cristina, Limarie and Khrisia for CIAM 6117

1. Wastewater Discharge Impacts
On Estuary Nutrient Dynamics
from Two Downstream Watersheds:
Río Piedras and Río Grande de Manatí
Co-Principal Investigators
Cristina I. Maldonado Morales -UPRRP
Limarie J. Reyes Torres -UPRRP
Khrisia A. Torres Camacho-UPRRP
CIAM 6117

2. Research Problem
● Wastewater discharges is one of the most severe environmental problems affecting
water bodies (including estuaries) in Puerto Rico.
● Contribute significant amounts of nutrients (nitrogen (N) and phosphorus (P))
causing water quality degradation:
○ eutrophication
○ accelerated plant growth
○ algae blooms
○ low dissolved oxygen (hypoxia)
○ death of aquatic animals

3. Research Problem
● Wastewater treatment plants (WWTPs) and failing septic systems are
sources of N and P into aquatic systems.
● In Puerto Rico:
○ Only 65% of the population is connected to sewer service from the
Puerto Rico Aqueduct and Sewer Authority (PRASA).
○ The exact amount of existing septic systems is unknown.
○ Accurate quantity measures of wastewater entering our estuaries is
unknown.
○ Little is known about the damage and water quality deterioration
occurring in estuaries due to wastewater discharges.

4. Goals and Objectives
● Main Goal: assess and compare the effects of anthropogenic nutrient inputs (N and P) from
wastewater discharges of two different watersheds into two estuarine ecosystems.
○ Objective 1: Determine if external sources of nutrients derived from wastewater are
present in both watersheds.
■ Hypothesis: External sources will be present in both watersheds.
○ Objective 2: Determine if the N and P loads will be higher in one watershed when
comparing one another.
■ Hypothesis: N and P loads will be higher in the Río Piedras watershed.
○ Objective 3: Determine if N and P gradients exist and evaluate their patterns.
■ Hypothesis: N and P gradients exist and will decrease from upstream to
downstream.

5. Goals and Objectives
● Gather sound scientific information that aids in the development and
implementation of policies to:
○ Improve wastewater disposal management strategies.
○ Protect and restore water quality in watersheds and estuaries.
● This research project aligns with the goals and strategies of the UPR Sea Grant
2014-2017 Strategic Plan as research focused on the area of Healthy
Ecosystems and Habitats - Estuaries
○ Coastal water quality degradation
○ Influence of anthropogenic activities on coastal ecosystems

6. Methods:Sampling Sites
Rio Piedras Watershed and Río Grande de Manatí Watershed
www.recursosaguapuertorico.com

7. Rio Piedras Watershed
Google Earth
DRNA Watershed data
Drainage Basin Area: San Juan/49km2
(DNER)
Climate: Moist Subtropical ((DNER)
Average Rainfall: 77”(rainy season); 53”(dry season) (DNER)
Geology: mostly volcanic (DNER)
Population: 259,595 (Census)
Land Use: 77% Urban, 21% Forest/Pastures,
0% Agriculture (USFS)
Wastewater Discharges: PRASA: One WWTP, effluent
to Atlantic Ocean (avg. of 56.6 mgd)
Non-PRASA: USGS, EQB data
show sewage discharges from
septic tanks (DNER)
Data sources:
DNER-Department of Natural and Environmental Resources of Puerto Rico,2004
Census-“Junta de Planificación” 2010 Census
USFS-United States Forest Service, 2011
DRNA Watershed data

8. Río Grande de Manatí Watershed
Drainage Basin Area: Orocovis, Barranquitas, Ciales,
Manatí and Barceloneta/608 km2
(DNER)
Climate: Moist Subtropical (DNER)
Average Rainfall: 77”(rainy season); 53”(dryseason) (DNER)
Geology: Karst, volcanic (DNER)
Population: 127,000 (DNER)
Land Use: 60% Forest and Pasture,
5% Urban,6% Agriculture(UPRRP-GSP)
Wastewater Discharges: PRASA: Three WWTPs
Watershed no longer meets the applicable water quality standards for
Puerto Rico (EQB)
Google Earth
DRNA Watershed data
Data sources:
DNER-Department of Natural and Environmental Resources of Puerto Rico,2004
EQB- Enviromental Qulality Board, 2010
UPRRP-GSP- N. Valentín,UPRRP Graduate School of planning,2010)

9. Sampling Sites: Río Piedras Watershed
Modified from Department of Natural and Environmental Resources of Puerto Rico Watershed Data

10. Sampling Sites: Río Grande de Manatí Watershed
Modified from Department of Natural and Environmental Resources of Puerto Rico Watershed Data

11. Methods: Phosphorus and Nitrogen determination
Hach, Total Phosphorus Test Kit Hach, Total Nitrogen Test KitLaMotte 2020we Kit
Portable Turbidity Meter
http://www.hach.com/phosver-3-phosphate-reagent-powder-pillows-25-ml-pk-100/product?id=7640196804 http://www.lamotte.com/en/water-wastewater/instrumentation/1970.html
http://www.hach.com/drb200-digital-reactor-block-15-x-16-mm-vial-wells-115-
vac/product?id=7640453262#
http://www.hach.com/nitrogen-total-tntplus-lr/product?id=7640209878
http://www.hach.com/total-nitrogen-reagent-set-lr-tnt/product?id=7640209858
● Total Nitrogen Persulfate Digestion Method
● Measures all forms of nitrogen present in the
water samples
● Acid Persulfate Digestion Method
● Measures all forms of phosphorus
present in the water samples
● Measures how much the material
suspended in water decreases the
passage of light through the water.

12. Methods: Data Collection and Analysis
Nutrient Loads and Discharge data
● WWTP discharge values will be taken from the National Pollutant Discharge Elimination System permits
● Watershed discharge values will be taken from the USGS streamflow data sampling points
Analysis
● Monthly and annual
○ average discharge values
○ nutrient concentrations
○ nutrient loads
● T test to determine significant differences
○ nutrient and river discharges
○ dry and rainy seasons

13. Activities/Timetables
2016 J F M A M J J A S O N D
Public Outreach x
Water sampling x x x x x x x x x x x x
Data Analysis x x
Web page creation x x
2017 J F M A M J J A S O N D
Public Outreach x
Water sampling x x x x x x x x x x x x
Data Analysis x x x x
Final Report / Paper
publication
x x x

14. 1. Raised awareness by public outreach.
2. Results will have short, medium and long term impacts because the data collected can be
used to:
○ Evaluate how nutrient flows vary in the watershed depending on the decrease or
increase of wastewater discharges.
○ Compare past and future studies in the two watersheds with our data.
3. Data collected can be used by government agencies, the academia and other interested
parties.
4. By providing a better understanding of the watersheds’ nutrient dynamics, this study will aid
in the development of appropriate technologies and management strategies that will protect
and restore coastal ecosystems and resources
Potential Benefits

15. Budget Summary
Total Request $ 28,676.64
Major Expenses $ 16,276.64
(Permanent equipments and wages)
Match Funding $ 30,000

16. Thank you for your attention
Photos by USGS, Caribbean Water Science Center Hydrologic Technicians
Río PiedrasRío Grande de Manatí