Guidance Manua pdf

 

46

or to achieve 10 ng/L MIB in finished water: 

 

PAC Dose (mg/L) = 10.8 x ln(MIB

raw

) – 24.8 

 

 

Equation 5.6 

 

 

Where the raw (MIB

raw

) and finished (MIB

finished

) water MIB concentrations are in ng/L.  

For example, if the influent MIB concentration is 30 ng/L and the desired effluent MIB 

concentration is 10 ng/L, a 20B PAC dose of about 11.9 ng/L would be required using 

the equation and 13.5 ng/L using the nomograph.  Practical operating curves were 

generated for future use of Norit 20B by all COP WTPs.  The operating curves are easy-

to-use nomographs that can be used instead of Equations 5.5 and 5.6, although the 

equations are more accurate than reading from the nomograph. 

 

Slurry storage of Norit 20B PAC at a full-scale WTP for approximately six-months did not 

effect its removal efficiency for MIB in raw water.  However, ordering and storage of PAC 

is critical for effective MIB removal.  On-site PAC storage should be based upon 

maximum PAC feed rates, maximum design WTP flowrate, and deliveries every five to 

seven days.  A schedule of PAC deliveries should be prepared and provided to PAC 

suppliers at least one month in advance.  PAC feed facilities should be designed to 

handle 40 to 50 mg/L of PAC.   

 

PAC doses should vary with flowrate and approximately weekly, based on GC/MS 

analysis of MIB and geosmin concentrations in raw and finished water.  Alternatively 

FPA can be used more frequently to adjust PAC dosages.  However, weekly 

confirmation by GC/MS should be included.  Costs for PAC may exceed $25,000 per 

week during MIB pulses (assuming 15 mg/L, 100 MGD, $0.30/lb PAC).  Therefore 

conducting GC/MS analysis for MIB of raw and finished water to optimize PAC dose 

(Equation 5.6) can  be extremely cost effective.  It is critical that the analytical laboratories 

know in advance of the MIB/geosmin sampling and the need for rapid (1 to 2 day) 

turnaround of the data.  All WTPs within a city should be sampled and analyzed on the 

same day (e.g., Monday) and PAC doses adjusted accordingly within two days (e.g., 

Wednesday), see Figure 3-1. 

 

5.5.3  Activated Carbon Filter Caps 

 

GAC capped filters operated in an adsorption or biologically active mode will remove 

some MIB and geosmin.  Existing anthracite filter caps could be replaced by GAC caps 

where MIB and geosmin removal is desired.  The GAC caps should be 30 to 50 inches in 

depth.  The point of chlorination should be after filtration to encourage biofiltration, which 

could affect CT disinfection credits.  Depending upon operating conditions 20% to > 90% 

MIB and geosmin removal can be achieved (Figure 5-11).

  

PAC addition may not be 

required when operating in adsorption modes only, while it would be required under 

biologically active modes (exhausted adsorption capacity).  GAC caps operated under 

adsorption mode, and to a lesser extent under a biodegradation mode, would provide 

TOC removal and removal of synthetic compounds (e.g., estrogenic compounds and 

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47

pharmaceuticals).  WTPs with short presedimentation contact times for PAC and/or high 

influent T&O concentration would benefit most by GAC filter caps.  GAC filter caps add 

another layer of treatment in a multiple-barrier approach to T&O control. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 5-11.  Breakthrough of MIB (upper) and geosmin (lower) in laboratory biofilters (from Malcolm Pirnie 

Inc. report to the City of Chandler). 

 

 

 

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48

5.5.4  Advanced Oxidation 

 

Ozone and UV irradiation can be effective at removing MIB and geosmin.  Ozone 

dosages capable of  Giardia and Cryptosporidium inactivation (2 to 4 mg/L) are capable 

of 80% to > 95% oxidation of MIB and geosmin in CAP or SRP water.  Ozone dosages 

of 2 to 4 mg/L will form bromate, and depending upon the initial bromide concentration in 

the raw water (80 to 150 

µ

g/L), bromate concentrations approaching the MCL of 10 

µ

g/L 

would be formed.  Therefore, acid and/or ammonia addition prior to ozonation would be 

required.  However, if ozone was used primarily for T&O control, lower ozone dosages 

(e.g., 0.75 mg/L) could achieve significant MIB removal (e.g., 60% to 80%). 

 

UV irradiation dosages required for MIB or geosmin oxidation are approximately 100 

times greater than dosages used for microbial inactivation.  Therefore, UV-irradiation 

probably is not cost-effective.   

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SECTION 6 

PROGRAM ASSESSMENT  

 

6.1  CONTINUOUS EVALUATION AND COMMUNICATIONS 

6.1.1  Rationale 

 

One of the keystone concepts of the T&O management program is rapid response.  It is 

now possible to collect and analyze water samples within 2-3 days, allowing week-by-

week evaluation of the T&O situation.  This makes it possible to respond quickly, 

implementing one or more control measures as needed. 

6.1.2  Implementation 

A T&O Newsletter was developed for this purpose.  Section 3 discusses the rationale 

and goals of the  Newsletter.  The  T&O Newsletter should be written and distributed 

weekly during the T&O season, roughly June through October.  As a minimum, the 

Newsletter should contain the latest sampling data and recommendations for PAC 

dosing and other implementation measures.  The format should be consistent from 

week to week, to make it easy for COP staff to find important information quickly.  

Electronic distribution via email attachment has worked very well.  COP should 

encourage technical staff to utilize the T&O Newsletter to share observations, treatment 

concepts, water delivery forecasts, and other ideas with WSD staff.   

 

6.2  ANNUAL (END OF YEAR) EVALUATION  

6.2.1  Rationale 

 

The T&O management program should continuously improve in the face of changing 

circumstances.  Accomplishing this requires continuous evaluation of the program as it 

evolves.  Thoughtful technical evaluation can document success, which can improve the 

public image of the WSD and improve staff morale, but is also needed  to identify 

weaknesses.  An annual evaluation could also be used to justify the cost of new 

facilities and equipment needed to improve the quality of water delivered to consumers. 

 

6.2.2  Elements of the Annual Evaluation 

 

The annual evaluation should include an evaluation of the quality of water delivered to 

customers each year, a review of operational issues, and an analysis of economic and 

institutional issues. 

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