Transcript Performance of Stormwater Filters with Low Cost Materials

Dr Kiran Tota-Maharaj
Senior Lecturer in Water & Environmental Engineering ,
University of Greenwich, UK
Dr Denver Cheddie
Associate Professor in Mechanical Engineering ,
University of Trinidad and Tobago
Trinidad &
Tobago
SE islands of Antilles, situated between 10° 2' & 11° 12' N latitude and 60° 30' & 61° 56' W
longitude. At the closest point, Trinidad is just 11 km off the Venezuelan coast.
Agricultural products include citrus, cocoa, coconuts and other products.
Recent growth has been fueled by investments in liquefied natural gas, petrochemicals,
& steel. It is the leading Caribbean producer of oil and gas, and its economy is heavily
dependent upon these resources but it also supplies manufactured goods, notably food
and beverages, as well as cement to the Caribbean region. Oil & gas account for 40% of
GDP & 80% of exports, but only 5% of employment.
Outline
 The Caribbean Coconut Industry
 Flooding in Rural Caribbean Communities
 Storm water filtration
 Purpose of research
 Filters analysed
 Results
Brown/mature coconut produces fibres
Dry coconuts used to make several
nutritious foods & beverages
Green Coconuts Water & Jelly
(Gelatinous inner part) Consumption
Waste Product sent to Landfills
Surface Water Flooding Problems
 Trinidad and Tobago
 2 seasons – dry and wet
 Wet season characterised by flash flooding
 Flood waters contain pollutants
 Water supply to rural communities come from surface
water
Stormwater Filters
 Source control approach to flood waters
 Filters remove pollutants
 Improves water quality
Schematic of Typical Sand/Gravel
Filter for stormwater
management across the
Caribbean
Stormwater Filters
 Typical filters are expensive for rural Caribbean
communities
 Clog easily and requires periodic backwashing and
maintenance
 Several communities across Trinidad and Tobago have
not adopted Sustainable Drainage Systems
Purpose
 To produce low cost stormwater filters constructed
from readily available materials (Coconut Husk/Fibres)
 To apply Low-impact development (LID) practices
through sustainable waste management techniques
 To alleviate Flash flooding & Urban Flooding across
Small Island Developing States (SIDS) through the
applications of Sustainable Drainage Systems (SuDS)
Three (3) Stormwater Filters
Investigated
ASCE/ US EPA (2000). Determining Urban Stormwater Best
Management Practice Removal Efficiencies.
ASCE/US EPA Database. International Stormwater Best
Management Practices (BMP) Database
Three (3) Stormwater Filters
Investigated
Stormwater Sampling & Analysis
 Obtained from 2 villages in Trinidad
Quantity Measured How Measured
pH
Thermo scientific Orion 3 star branch top meter
Chemical Oxygen
Demand (COD)
Hach DRB200 reactor block and DR500
spectrophotometer
Nitrates / Nitrites
Spot sampling
Phosphates
Spot sampling
Total suspended
solids (TSS)
Filtration method
Total dissolved solids Evaporation method
(TDS)
APHA, AWWA, WEF. Standard
Methods for examination of water
and wastewater. 22nd ed.
Washington: American Public Health
Association;
(2012)
Turbidity
Turbidity meter
Conductivity
Jenway 4520 conductivity meter
Coliforms
Membrane filter technique
Results
Filter (1) Coconut Husk/Fibres & Gravel Media
Filter (2) Sand & Gravel Media
Filter (3) Pea gravel, Gravel & Coconut Husk/Fibres Media
January- December 2014 (Sample number n = 190)
Results
Filter (1) Coconut Husk/Fibres & Gravel Media
Filter (2) Sand & Gravel Media
Filter (3) Pea gravel, Gravel & Coconut Husk/Fibres Media
Comparison of bacterial (total coliforms) survival versus time for stormwater filters 13, (Sample number n = 45, January-June 2014)
Results Cont’d
 Filters significantly reduce nitrates, nitrites, TSS & TDS
 High removal rates for coliform levels
 Relatively good reduction in COD (20-70 %), phosphates
(10 %), turbidity (30-60 %)
 There were no significant differences in water quality
effluents for all three filters (p > 0.05, according to
ANOVA)
 Filters performed well in treating water & producing
cleaner effluent water for non-potable purposes (water
recycling e.g. washing cars, agriculture etc.)
 No clogging noticed during one-year period of operation
Conclusion
 Coconut fibre filters are good for improving the quality
of stormwater treatment & urban runoff control
especially during the rainy season (July-December)
 Results from water quality analysis found the water
outflows from filters were not applicable for drinking
purposes (according to WHO)
 Filters are low cost & disposable (eventually sent to
Landfills or used in alternative applications)
 No need for backwashing
 Viable source control approach to stormwater pollution
Acknowledgements
The research was supported by The University of Trinidad &
Tobago, Point Lisas Campus, Trinidad, West Indies. The authors
would like to acknowledge Professor Mahendra Thakur (recently
retired Professor) from the Department of Mechanical
Engineering, University of Trinidad and Tobago for supporting
this research initiative.
We would also like to thank the technical staff within the
Department of Utilities Engineering in the University of Trinidad
and Tobago for their support in carrying out the experimental
project work.
Thank you for listening.