טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentGuy Furer
SubjectA Decision Support Protocol for Cost-effective Retrofit
Strategy of an Existing WWTP for
Enhanced Biological Phosphorus Removal
(EBPR)
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Emeritus Galil Noah (Deceased)
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

Environmental and legislative constraints bring about a need to adjust existing wastewater treatment plants (WWTPs), designed and built for the removal of carbonaceous substrate and sometimes also nitrogen compounds, for enhanced biological phosphorus removal (EBPR).

Most of the phosphorus in nature is in the form of phosphates, mainly PO4-3, HPO4-2, P2O7, and organically-bound. These are the compounds targeted in EBPR.

Upgrading a WWTP for EBPR is complex and expensive, requiring expertise in many different fields. 

This work aims at giving the decision maker which is not a wastewater treatment professional technical and economic estimation abilities in the upgrading of an existing WWTP for improved levels of phosphorus removal, outlining also the essentials of COD, Nitrogen, and Suspended Solids removals. It also describes the essentials of chemically enhanced phosphorus removal. 

Using metal salts (Alum, FeCl3, or NaAlO2), might be cost effective in achieving very low phosphorus levels (0.05-0.2 ppm), because the biological alternative usually includes constructing anaerobic volumes.    

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EBPR might be cost effective in achieving medium-to-low phosphorus levels (2-5 ppm and higher), especially when external rbCOD (ethanol, methanol, molasses, and other industrial or agricultural streams) is available.

Model runs had shown that:

-          For effluent P levels above 2 ppm: in low (up to 50,000 SCM/d) and medium (up to 200,000 SCM/d) flows, chemical P removal is economically favorable; in higher flows, biological P removal is favorable.

-          For effluent P levels below 2 ppm, combined (biological chemical) P removal is economically favorable.

-          Bigger WWTPs cost more to retrofit, but retrofitting them is more worthwhile calculated per SCM.

-          in WWTPs that are not activated-sludge-based, such as SBR processes, there is no possible way to implement EBPR as a part of the existing process, and the only relevant retrofit option is the addition of metal cation salts. Stricter demands will require the addition of more cation.

-          Wastewater characteristics are a crucial factor in the possibility and cost-effectiveness of EBPR:

-          Sludge stabilization processes produce flows that are rich in phosphorus, with TP concentrations of 100-250 ppm. These might have an adverse impact on phosphorus removal ability of the WWTP, and therefore must be considered, calculated, and compensated for.

The work consists of a detailed handbook, and an electronic interactive spreadsheet. Both can be used to produce basic estimates of the configuration, sizes, and costs of the required retrofit.