Grantee Research Project Results
Final Report: Dose Controller for AguaClara Water Treatment Plants
EPA Grant Number: SU834338Title: Dose Controller for AguaClara Water Treatment Plants
Investigators: Weber-Shirk, Monroe , Swetland, Karen A. , Johnson, Dale , Patel, Akta , Curtis, Kayti , Ko, Harrison
Institution: Cornell University
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2009 through August 14, 2010
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2009) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
Currently 1.2 billion people do not have access to clean water. This staggering statistic demonstrates the overwhelming need for improved access to potable water, especially in low income rural areas in the Global South (or “Developing World”). The reduction in water borne diseases is a major public health priority nationally and internationally. AguaClara is a program in Civil and Environmental Engineering at Cornell University committed to improving access to improved drinking water quality in the Global South. After numerous failed attempts at using technologies developed for the Global North to provide water treatment to the Global South, a new alternative for the delivery of sustainable water systems is being explored. AguaClara is committed to the sustainable, locally available, and replicable model of water treatment design delivery. There are currently nine research and design teams in AguaClara committed to expanding our current understanding of water treatment.
The primary objectives of an AguaClara plant are to remove much of the suspended dirt particles present in the source water and to kill disease causing pathogens through disinfection. Turbidity is a measure of the cloudiness of the water and is a key indicator of water quality. A chemical coagulant, alum, is added to the raw water intended to improve the turbidity of water by causing suspended solids to stick together and settle out. The agglomeration of suspended solids decreases the turbidity of the water and has significantly reduced incidences of water borne illnesses.
The nonlinear chemical dose controller provides a means for alum to be accurately dosed regardless of the size of the plant. Previous designs for the dosing of alum in AguaClara plants were using a linear orifice meter, with its accuracy limited by the plant flow rate. The orifice-controlled nonlinear chemical doser allows AguaClara plants to be scaled up to much higher flow rates without a loss of the accuracy of alum dosing. In addition, the doser automatically adjusts the flow of alum to maintain a specified concentration in alum in the influent matter, even with changing plant flow rates. All of this is done without electricity. The accurate and reliable dosing of alum will greatly improve the flocculation and sedimentation process and improve the overall quality of treated water.
Figure 1: Nonlinear dose controller being installed in Agalteca, Honduras
Summary/Accomplishments (Outputs/Outcomes):
Since the phase I award in the EPA P3 competition, many strides have been made towards the successful implementation of a robust design for the dosing of alum in AguaClara plants. We set out to make a doser which might serve as a model for future AguaClara plants and provide proof of the applicability of the conceptual theory behind the orifice-controlled nonlinear chemical dose controller. Many of the design constraints bounding the implementation of the project have been identified and explored as to their potential impact on the effectiveness of the doser.
The nonlinear chemical dose controller is able to dose over a much higher range of plant flow rates than previous linear models of alum dosing systems. This feature will allow future AguaClara plants to scale up to any desired plant flow rate, and accurate dosing can still be consistently achieved. The scalability of the dosing apparatus is extremely important since AguaClara is committed to providing the capability for anyone in the world to automatically generate a design for a water treatment plant, regardless of the size. In addition, the nonlinear doser has been designed to greatly increase the accuracy to which alum is dosed. The dual scaled lever arm allows for a much broader range of dosages to be reached, spanning from 5 mg/L to 100 mg/L. The operator of an AguaClara plant will be able to have much greater flexibility to dose at the alum range that is most appropriate, based on varying levels of influent water turbidity. The selected concentration will be maintained regardless of variations in the plant flow rate. A float connects the lever arm of the doser to the water level in the entrance tank of the plant so the flow of alum corresponds to the flow of raw water. As the water level in the entrance tank increases, so does the flow rate of alum. This allows for an automated dosing system which will significantly reduce errors caused by the operator and increase overall performance of the plant by providing reliable, accurate alum dosing.
A nonlinear chemical doser has been constructed and installed in an AguaClara plant in Agalteca, Honduras. The testing of our doser in a fully operational water treatment plant will provide useful ‘real world’ verification of our doser design as well as assist in the identification of unforeseen problems which might occur in the course of its operation. In this regard, future designs might be adapted to accommodate identified problems. Close contact is maintained with designed AguaClara plants long after the construction has been completed for each plant. A communication loop is created whereby problems are identified at a plant and relayed back to Cornell, where our design and research teams actively work to solve those problems. This contact not only improves the performance of existing plants but provides feedback to inform future designs.
Conclusions:
The accurate dosing of alum in any water treatment system is essential to maintain high quality of treated water. In this respect, the nonlinear chemical dose controller, with a nonlinear dual scale and orifice-controlled flow, facilitates accurate, reliable dosing regardless of the plant flow rate. This innovation will allow AguaClara plants to scale up in flow rate to any size without adverse affects in alum dosing reliability. Many improvements have been made over previous linear AguaClara alum dosers, and will provide a viable means of alum dosing for any future planned treatment plants.
A working model of the nonlinear chemical doser has been created and installed in an AguaClara plant in Agalteca, Honduras. The real world application of the doser will provide valuable insights into the long term reliability of the doser as well as potential failure mechanisms. Much progress has been made in the development of the nonlinear chemical doser yet significant testing remains. Future research will focus on validation testing, failure mode mechanisms, and the conversion to alternative locally available materials.
Supplemental Keywords:
chemical dose controller, surface water treatment, turbidity, gravity powered, sustainable, alum, Global SRelevant Websites:
Nonlinear Chemical Dose Controller Exit
P3 Phase II:
Chemical Doser for AguaClara Water Treatment Plants | 2011 Progress Report | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.