Operating Chemically Enhanced Clarification for Optimum ...CEC processes were tested at the South Shore WWTP: DensaDeg®, manufactured by Infilco Degremont, and ACTIFLO®, manufactured

Operating Chemically Enhanced Clarification for Optimum Disinfection Performance

Thomas Sigmund, John Siczka, Todd Elliott, Jamal Awad, CH2M HILL Richard Onderko, Milwaukee Metropolitan Sewerage District

ABSTRACT The Milwaukee Metropolitan Sewerage District conducted demonstration tests in 2005 to evaluate chemically enhanced clarification (CEC) of wet-weather flows at the District’s two wastewater treatment plants (WWTPs). CEC offers the potential to treat intermittent high wet-weather flows, produce high-quality effluent, and fit into the limited space at the plant sites. Two CEC processes were tested at the South Shore WWTP: DensaDeg®, manufactured by Infilco Degremont, and ACTIFLO®, manufactured by Krüger. Primary clarifier influent was the wastewater source, and it was split between the two CEC processes. Testing was conducted during both dry- and wet-weather conditions.

The CEC demonstration testing program had the following specific objectives: evaluate the performance of the selected CEC technologies, evaluate the feasibility of UV disinfection for CEC effluent, compare CEC treatment to existing secondary treatment, and determine key design criteria for full-scale application of CEC for wet-weather flows at Jones Island and South Shore WWTPs.

The CEC demonstration testing at the South Shore WWTP provided a wealth of data that assisted the District in conceptual design evaluations of wet-weather treatment alternatives. The CEC processes provided high levels of treatment at very high overflow rates, minimizing their footprint for inclusion at either the Jones Island or South Shore WWTPs.

KEYWORDS Chemically Enhanced Clarification, High Rate Treatment, Wet-Weather, Disinfection, Pathogens

INTRODUCTION The Milwaukee Metropolitan Sewerage District operates two wastewater treatments plants (WWTPs) with a combined peak hour capacity of 630 mgd (2,385,000 m3/d). Following major storms in the service area, wastewater flow into the system can exceed 1 billion gallons per day (3,785,000 m3/d). Significant storage capacity within the system offsets the need to provide treatment capacity equal to the peak daily flow. However, the District’s 2020 Facilities Plan is evaluating alternatives for increasing treatment capacity during major storms.

METHODOLOGY The District and its consultant, CH2M HILL, conducted demonstration tests in 2005 to evaluate chemically enhanced clarification (CEC) of wet-weather flows at either of its two wastewater treatment plants. CEC offers the potential to treat intermittent high wet-weather flows, produce high-quality effluent, and fit into the limited space available at the Jones Island and South Shore plants. Testing was conducted during both dry-weather and wet-weather conditions. Disinfection effectiveness on CEC effluent was measured during those tests in terms of removal of E. coli, fecal coliform and male-specific coliphage (as a surrogate for human viruses). During wet-

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Copyright 2006 Water Environment Foundation. All Rights Reserved©

weather events, additional analysis was performed for inactivation of viruses, Cryptosporidium, and Giardia. The CEC processes provided high levels of treatment at very high surface overflow rates, minimizing their footprint to allow inclusion at either Jones Island or South Shore.

Two CEC processes were recommended for onsite demonstration testing: DensaDeg®, manufactured by Infilco Degremont (Exhibit 1), and ACTIFLO®, manufactured by Krüger (Exhibit 2). The demonstration testing collected additional operating information to allow the project team to complete the technology evaluation and develop conceptual designs. Since CEC effluent requires disinfection, the demonstration test program also collected information to evaluate the effectiveness of ultraviolet (UV) light on CEC effluent. Demonstration testing was conducted at South Shore from April 28 until July 6, 2005.

The CEC demonstration testing program had the following specific objectives:

• Evaluate the performance of the selected CEC technologies.

• Determine key design criteria for full-scale application of CEC and UV disinfection for wet-weather flows at the Jones Island and South Shore wastewater treatment plants.

• Conduct a general performance comparison of CEC/UV treatment to existing treatment processes.

EXHIBIT 1DensaDeg Process (taken from Infilco Degremont document)

EXHIBIT 2 ACTIFLO Process (taken from Krüger document)

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The DensaDeg and ACTIFLO systems both employ CEC, a physical-chemical treatment process in which coagulants and flocculants are used to create conditions under which dense flocs with a high settling velocity are formed, allowing them to be removed efficiently at high surface overflow rates with corresponding high TSS and particulate BOD5 removal. The DensaDeg system attaches chemical sludge produced within it (recirculated inside the clarifier) to the incoming solids to increase density and enhance removal. The ACTIFLO system incorporates microsand in the floc to increase density of the flocs to enhance removal.

The skid-mounted UV disinfection demonstration unit (Exhibit 3) provided by Trojan Technologies employed the UV4000™ medium pressure, high intensity, UV disinfection technology. The unit had eight variable output UV lamps (capable of modulating power settings from 30 to 100 percent) arranged in two banks each with a two-by-two matrix. The lamps were equipped with an automatic chemical and mechanical cleaning system.

The setup of the demonstration testing equipment at the South Shore WWTP is shown in Exhibit 4.

EXHIBIT 4 Demonstration Testing Setup

RESULTS Considerable coagulant optimization testing was performed on primary clarifier influent. Coagulants (ferric chloride and aluminum sulfate) were evaluated at various doses to achieve the

EXHIBIT 3Trojan Mobile Pilot Unit

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desired BOD5 and TSS removals from the CEC process (at least 50 percent removal for BOD5, 85 percent removal for TSS, and to maximize UVT). Considerable surface overflow rate testing was also performed to evaluate the reliability and robustness of the CEC units under various operating conditions. The testing showed that the CEC units could handle higher than design overflow rates without significant increases in effluent TSS.

Specific wastewater characteristics and wastewater treatment process chemicals were unexpectedly found to interfere with CEC and to render UV disinfection infeasible. The Jones Island WWTP receives wastewater from several industries including a yeast plant. Bench- and pilot-scale tests indicated that even relatively small volumetric contributions of yeast plant wastewater to the Jones Island WWTP significantly reduced CEC performance and reduced UVT below levels generally acceptable for UV disinfection. Exhibit 5 shows the impact of various amounts of yeast plant wastewater added to the South Shore WWTP primary influent. As little as 0.1 percent by volume added to typical WWTP influent had a significant impact on the treatability and UVT of the wastewater.

The yeast plant wastewater interfered greatly with coagulation and flocculation in CEC. The yeast plant wastewater also imparts a strong color to the WWTP influent that is not significantly reduced by CEC. Medium pressure UV lamps emit approximately 90 percent of their light energy between 200 and 300 nanometers. As shown in Exhibit 6, the color bodies in the yeast plant wastewater have a maximum light absorbance overlapping this point in the UV spectrum.

EXHIBIT 5 Impact of Yeast Plant Process Wastewater Addition to South Shore Primary Clarifier Influent

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EXHIBIT 6 Spectral Scan of Yeast Waste

The South Shore WWTP uses either pickle liquor (an inexpensive byproduct of manufacturing as ferrous iron) or ferric chloride as an iron source for phosphorus control. The plant adds the chemicals upstream of primary treatment. Both ferrous and ferric iron remove phosphorus, (ferrous must be oxidized first) but their coagulation properties differ. The presence of pickle liquor in the South Shore primary clarifier influent adversely affected TSS removal and caused instability in the CEC units. Exhibit 7 shows the influence of pickle liquor on the color of the wastewater. Ferrous iron also caused rapid fouling of the UV quartz sleeves (Exhibit 8). The same fouling effects were not observed when ferric chloride was used for phosphorus removal.

EXHIBIT 7 Wastewater at Various Stages of Treatment

From left to right: screened and degritted wastewater upstream of pickle liquor addition; primary clarifier influent with pickle liquor; primary clarifier effluent with pickle liquor; and DensaDeg effluent without pickle liquor.

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EXHIBIT 8 Fouled Quartz Sleeves (left) and Clean Quartz Sleeves (right)

DISCUSSION The interferences of yeast plant wastewater could not be overcome in pilot testing. Subsequently, pilot testing was limited to the South Shore WWTP, which does not have yeast plant wastewater as an influent component. (Incidentally, the yeast plant closed after the completion of the pilot

EXHIBIT 9 Impact of Pickle Liquor on CEC Effluent

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testing). Based on successful testing at the South Shore WWTP, application of CEC at the Jones Island WWTP is considered feasible without the influence of the yeast plant wastewater.

Once it was confirmed that pickle liquor interfered with CEC and was the source of fouling of the UV quartz sleeves, the CEC influent was relocated upstream of the pickle liquor addition point. Without pickle liquor in the primary clarifier influent, both the ACTIFLO and DensaDeg units performed well at South Shore (Exhibit 9). Both units exhibited excellent stability and achieved 87 percent or greater TSS removal and 58 to 68 percent BOD5 removal with either alum or ferric chloride. UVT values generally were between 55 and 65 percent, making UV disinfection a feasible option.

During testing at South Shore, several issues in addition to pickle liquor addition adversely affected the performance of UV disinfection, including ferric chloride addition in CEC units, high levels of TSS, and surface overflow rates greater than the design point.

Several extended operation verification demonstration tests were conducted for the CEC units. Exhibit 10 summarizes the results of extended run tests conducted on primary influent under optimized operating conditions. Both units exhibited excellent stability and achieved 90 percent or greater TSS removal and 60 percent or greater BOD5 removal with either alum or ferric chloride. BOD5 of the CEC effluent did not meet South Shore’s effluent limits of 30 mg/L for a 30-day average or 45 mg/L for a 7-day average. Particulate BOD5 (pBOD5) removal was greater than 95 percent, and the average total phosphorus in the CEC effluent ranged from 0.3 to 0.4 mg/L. UVT values generally were between 55 and 65 percent, high enough for UV disinfection of CEC effluent to be practical. During two storms, both CEC units showed excellent stability. The average TSS concentration in the CEC effluent was less than 20 mg/L and the average BOD5 concentration ranged from 40 to 80 mg/L.

Exhibit 11 shows performance for CEC with respect to TSS and

EXHIBIT 10 Treatment Performance for Extended Run Tests Conducted on Primary Influent

Parameter ACTIFLO DensaDeg

Average TSS 13 mg/L 11 mg/L

% TSS Removal 93 94

Average Turbidity 5.9 ntu 5.3 ntu

Average BOD5 65 mg/L 57 mg/L

% BOD5 Removal 62 67

Average pBOD5 3.5 mg/L 0.1 mg/L

% pBOD5 Removal 96 99.3

Average Tot. P 0.4 mg/L 0.3 mg/L

Average UVT 58 61

Average pH 6.7 6.5

EXHIBIT 11 Impact of Coagulant Type and Dose on UVT and TSS

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UVT at various coagulant dosages. DensaDeg performed slightly better than ACTIFLO and was able to achieve a TSS concentration of less than 10 mg/L and a UVT of close to 60 percent at nearly all doses tested. ACTIFLO, on the other hand, was able to achieve effluent TSS concentrations less than 10 mg/L only with an alum dose of 225 mg/L. The high coagulant dosages were tested on dry weather flows to determine the increase in UVT and resulting savings in sizing of UV equipment. These high dosages may reduce pH if alkalinity of wet-weather flows is significantly lower than for dry weather flows. Low total suspended solids are not required for the WWTP chloramine disinfection currently practiced, and the recommended coagulant doses can be reduced when compared to UV disinfection.

DISINFECTION Fecal coliform bacteria are a subgroup of coliform bacteria. The presence of fecal coliforms in water indicates that fecal contamination of the water by a warm-blooded animal has occurred. E. coli is a rod-shaped bacterium commonly found in the gastrointestinal tract and feces of warm-blooded animals and is a member of the fecal coliform group of bacteria. Its presence provides direct evidence of fecal contamination from warm-blooded animals. It is usually harmless, but some strains can cause illness. Fecal coliform bacteria, an indicator for microbial pathogens in wastewater, are typically found at 105 to 107 CFU per 100 mL in untreated wastewater (NRC 1996).

Exhibit 12 shows typical CEC and UV disinfection performance at selected optimized operating conditions. The detection limits for fecal coliform and E. coli were 33 CFU/100ml and 100 MPN/100ml, respectively.

Exhibit 13 compares the effect of alum and ferric coagulation on downstream UV disinfection. By applying a UV dose of 40 millijoules per square centimeter (mJ/cm2) to the alum treated

EXHIBIT 12 UV Disinfection Performance on CEC Treated Primary Influent @ 200 mg/l Alum Addition

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wastewater, the UV disinfection system achieved a 2.9-log reduction of fecal coliform and a 2.6-log reduction of E. coli. On the other hand, applying an even higher UV dose of 60 mJ/cm2 to the ferric treated wastewater achieved only a 0.40-log reduction of fecal coliform and a 0.41-log reduction of E. coli. Ferric chloride interferes with UV disinfection by absorbing UV light and creating a shadow/shield effect for bacteria and viruses attached to the ferric chloride floc.

About 1 to 2.5 log10 reduction of E. coli and fecal coliform was achieved through the CEC units, which is similar to that achieved with primary and secondary treatment at South Shore. A 4 log10 reduction of E. coli and 5 log10 reduction of fecal coliform was observed after chlorine addition (chloramine disinfection) at the South Shore WWTP. Similar reduction of fecal coliform and E. coli was achieved by UV disinfection of CEC effluent at a UV dose of 40 mJ/cm2, as long as the CEC process reduced TSS levels below 20 mg/L and alum was used as the coagulant.

EXHIBIT 13 Impact of Alum and Ferric Coagulation on Downstream UV Disinfection Performance

A UV dose of at least 40 mJ/cm2 was required to reduce the fecal coliform concentration to less than 400 MPN/100 mL, the 30-day WPDES permit limit, and to achieve levels of disinfection similar to that of the chloramine disinfection system. The ACTIFLO effluent required about a 10 mJ/cm2 higher UV dose than the DensaDeg effluent in the UV dose range of 40 to 60 mJ/cm2 to achieve similar reductions of E. coli.

Bacteriophages (phages) are viruses that infect bacteria, and all bacteria have specific bacteriophages that will infect them. Coliphages are viruses that specifically infect and replicate E. coli bacteria, therefore the presence of coliphages in water can indicate the presence of their host, E. coli. Male-specific coliphages, or F+ coliphages, are similar to human enteric viruses in terms of morphology and survival characteristics, with the advantage as an indicator organism of being more stable in environmental water and more resistant to disinfection compared to human

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enteric viruses. Nieuwstad, et al. (1991) found male specific bacteriophages to be a suitable indicator organism for virus inactivation by UV disinfection in secondary wastewater effluent.

Exhibit 14 summarizes the observed log removal of three indicator organisms through the treatment processes observed in this demonstration study.

EXHIBIT 14 Observed Log10 Reduction of Indicator Organisms by Various Treatment Processes

Treatment Processes E. coli Fecal Coliform F+ Coliphage

CECa 1 to 2.5 log 1 to 2.5 log 2 to 3 log

Primary & Secondary Treatment at South Shore 1 to 2.5 log 1 to 2.5 log 1.5 to 2.5 log

CEC + UV Disinfectionb 3 to 4 log 3 to 5 log 3.5 to 4 log

Primary & Secondary Treatment + Chloramine Disinfection at South Shore

3 to 4 log 3 to 5 log 3 to 3.5 log

aAlum and ferric doses ranging from 80 to 150 mg/L. bAlum and ferric doses ranging from 200 to 250 mg/L and UV dose of 40 mJ/cm2.

Bacteroides is a genus of bacteria that can be detected specifically in human feces and sewage. They are the most common genus of bacteria in human feces and are opportunistic human pathogens. Bacteroides is also found in animals. Bacteroides is the anaerobic counterpart of E coli except they are somewhat smaller. Bacteroides were analyzed later in the demonstration study.

Cryptosporidium is a protozoan parasite that forms oocysts that can survive for extended periods in most environments. The oocysts are highly resistant to environmental pressures and are difficult to remove in water treatment because of their small size. Giardia lamblia, a protozoan parasite that infects numerous mammals, is found in the small and large intestines. Both of these protozoan parasites can cause human illness and are common test organisms for characterizing water quality. Cryptosporidium oocyst counts in sewage typically range from 102 to 105 oocysts per 100 liters and Giardia cyst counts from 10 to 104 cysts per 100 liters (NRC 1996). Chlorine disinfection is practically ineffective with Cryptosporidium. Chlorine disinfection is effective with Giardia, but a long contact time is necessary. Both organisms are highly resistant to inactivation by chloramines.

Enteroviruses and adenoviruses are classes of viruses that can cause illness in humans. Enteroviruses are readily found in wastewater and surface water and include polioviruses, coxsackieviruses, and echoviruses (Letterman 1999). Enteroviruses cause various illnesses, ranging from paralytic poliomyelitis (polio) to the common cold (Gerba 1999). In the U.S., enteric virus counts in sewage typically range from 103 to 104 plaque forming units (PFU) per 100 liters (NRC 1996). Historic data collected for Jones Island raw sewage have shown enteric virus counts ranging from 104 to 106 PFU per 100 liters. Human adenoviruses may cause acute respiratory disease, pneumonia, epidemic conjunctivitis, and acute gastroenteritis in children (Enriquez 1999). There are 47 known types of adenoviruses, but only enteric types 40 (Ead 40) and 41 (Ead 41) are important causes of gastrointestinal illnesses, especially in children (Letterman 1999). Adenoviruses are the class of viruses most resistant to UV disinfection.

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Levels of pathogenic organisms in raw municipal wastewater are highly variable and depend upon a variety of factors including the extent of infections in the population, the season of the year, and the methods used for their recovery and detection (NRC 1998). For example, enteroviruses tend to be more prevalent in the spring while rotaviruses are more common in the winter (Gerba et al. 1985, 1996).

E. coli, fecal coliform, and F+ coliphage were analyzed throughout the demonstration testing. Bacteroides were analyzed only at the end of the demonstration study. The original testing plan included testing for Cryptosporidium, Giardia, enteroviruses, and adenoviruses during four wet-weather events. However, only two wet-weather events (May 11 and 19, 2005) occurred over the 14-week test period. Because of the limited wet-weather events and the need to collect more pathogen data, Cryptosporidium, Giardia, enteroviruses, and adenoviruses samples were collected during dry weather testing on July 6, 2005.

Cryptosporidium and Giardia were analyzed for in the CEC, UV, primary clarifier, secondary clarifier, and chlorine contact basin effluents but could not be reliably detected in the primary influent, making calculation of removal efficiency through CEC and primary and secondary treatment impossible.

Giardia cysts and Cryptosporidium oocysts were enumerated using USEPA Method 1623 with modifications developed for optimal recovery in wastewater matrices. Samples first were seeded with ColorSeed as a measure of method performance. ColorSeed consists of flow-sorted, gamma-irradiated (dead) Giardia cysts and Cryptosporidium oocysts stained with a red dye. The percent recovery of ColorSeed compares method performance across different wastewater samples and is an indicator of performance for Giardia cyst and Cryptosporidium oocyst counts made using modified USEPA Method 1623. Low recovery indicates that an interference present in the wastewater matrix inhibits the isolation of ColorSeed from the contaminating debris using immunomagnetic separation. The interference may be chemical or biological. Low recoveries are an indicator of the difficulty in isolating the indigenous cysts and oocysts but are not an indicator of the absence of the target organism. Low recoveries can be reflected in low cyst and oocysts counts. For example, wastewater samples with dirtier matrices such as primary clarifier influent tend to have lower recoveries and lower cyst and oocyst counts than cleaner matrices like secondary clarifier effluent.

Cell culture methods were employed to analyze the infectivity of the recovered Cryptosporidium oocysts. No infectivity test method exists for Giardia cysts. A viability test exists for both Cryptosporidium oocysts and Giardia cysts, but infectivity is of greater value in disinfection because a viable oocyst or cyst may not be capable of causing infection.

Enteroviruses were cultured on the BGM (buffalo green monkey kidney cells) cell line. USEPA recommends the BGM cell line cultivable virus, and it largely picks up enteroviruses. Adenoviruses were cultured on the PRC/PRF/5 (human liver carcinoma cells) cell line. The laboratory selected the PRC/PRF/5 line because it is sensitive to detection of adenoviruses.

Acceptable recovery of Cryptosporidium oocysts and Giardia cysts was not achieved on the primary clarifier influent samples. Higher recoveries up to 68 percent were reported in the

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samples with less interference from solids like those found in the chlorine contact chamber effluent.

In all the sampling events, low counts of Cryptosporidium oocysts—fewer than one oocyst per liter—were detected in the secondary clarifier effluent and the chlorine contact basin effluent at South Shore and Jones Island; and none of the oocysts were infective.

Cryptosporidium oocysts were not detected in the DensaDeg effluent, but one sample of the ACTIFLO effluent had a Cryptosporidium count of two oocysts per liter. No infective oocysts were detected in the CEC or UV disinfection effluent.

Higher counts of Giardia cysts were observed than for Cryptosporidium oocysts. During the wet-weather sampling events, Giardia counts as high as 19.6 cysts per liter were observed in the South Shore chlorine contact chamber effluent. Giardia cysts were not detected in the DensaDeg effluent, but one sample of the ACTIFLO effluent had a Giardia count of two cysts per liter.

The levels of Giardia and Cryptosporidium observed in the secondary clarifier effluent are similar to levels reported in literature. Rose et al. (1996) reported levels of Giardia between 4.4 to 22.97 cysts/liter and Cryptosporidium of 1.4 oocysts/liter.

Although the results from the demonstration study were inconclusive, previous studies have reported the observed removal of Giardia and Cryptosporidium through various wastewater treatment processes. Rose et al. (1996, 1997) reported 1.19 log10 reduction of Giardia and 1.14 log10 reduction of Cryptosporidium, through biological treatment and clarification. An additional 0.65 log10 reduction of Giardia and 0.41 log10 reduction of Cryptosporidium occurred after a chlorine dose of 4 mg/L chlorine and 45 minutes of contact time. In comparison, the chloramines disinfection system at South Shore consists of a chlorine dose around 1.2 mg/L with a contact time of 30 to 60 minutes, depending on flow. Chemical flocculation and clarification with lime can achieve 2 log10 reduction of Cryptosporidium and Giardia, with the primary removal mechanism being physical removal (CH2M HILL 1993; Rose et al. 1997). Correspondence from MacDonald/MMSD has shown historic (1994-2000) log10 reduction of Giardia at Jones Island to be 1.69 log10 reduction of plant effluent compared to influent.

Since lower concentrations of Cryptosporidium oocysts and Giardia cysts were present in the CEC effluent than in the secondary clarifier effluent at South Shore, it can be speculated that CEC did a better job of removing those pathogens. Direct comparison of chlorine to UV disinfection was impossible because no infective Cryptosporidium oocysts were detected in any samples.

Total virus concentrations in the secondary effluent before chloramination ranged from 0 to 71.6 MPN/L and after chloramination from 0 to 34.6 MPN/L for both plants. Sedmak et al. (2005) reported a range of 0 to 233 MPN/L at the Jones Island plant after chloramination over a 9-year period. In the months of May through July when this demonstration study was conducted, Sedmak et al. (2005) found a range of 0 to 16 MPN/L with a mean of about 2 MPN/L. Sedmak’s 9-year study used a modified U.S. EPA Information Collection Rule organic flocculation cell culture procedure that included using Caco-2, RD, and HEp-2 cells in addition to BGM cells. Virus concentrations in wastewater vary seasonally and from year to year, depending upon the

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number of individuals infected in the community at any one time. Most viruses detected during the three sampling days were adenoviruses; there were only four detections of enteroviruses.

On May 11 and May 19, viruses were not detected in the ACTIFLO, DensaDeg, and UV effluents. The UV dose was between 25 to 30 mJ/cm2 on May 11 and 80 to 100 mJ/cm2 on May 19. Viruses were detected in the secondary clarifier effluent after chloramination at South Shore and Jones Island on both dates and on May 11 at Jones Island. On May 11, the total culturable virus concentration was reduced from 71.6 to 11.8 MPN/L across the chlorine contact basin at South Shore, equating to 84 percent reduction.

The highest levels of virus in the study were detected in the ACTIFLO (341 MPN/L) and DensaDeg (114 MPN/L) effluents on July 6. However, no viruses were detected after UV disinfection of the ACTIFLO effluent on July 6, indicating a greater than 99.7 percent reduction of the viruses. UV disinfection of the DensaDeg treated wastewater July 6 resulted in a 99 percent reduction of the viruses. The UV dose was 40 mJ/cm2 on July 6. One of the two samples taken of the secondary clarifier effluent at South Shore collected on July 6 yielded viruses (10.2 MPN/L). No viruses were detected in the chloraminated effluent.

Because viruses could not be reliably detected in the primary influent, measurement of virus removal through CEC also was not possible. The virus data suggested that UV disinfection with doses of 40 mJ/cm2 results in similar virus reduction to chloramines disinfection at South Shore (1 to 3 log10), which corresponded with reports in literature.

F+ coliphage may be used as a surrogate indicator for human enteric viruses like enteroviruses and adenoviruses in secondary wastewater effluent (Nieuwstad et al. 1991). During wet-weather sampling events, the concentration of F+ coliphage in the primary clarifier influent was 104 PFU/mL on May 11 and 12 PFU/mL on May 19. Concentrations of F+ coliphage were less than 10 PFU/mL in the both CEC effluents and South Shore secondary clarifier effluent. Concentrations of F+ coliphage were less than 1 PFU/mL in the UV effluent but as high as 8.1 PFU/mL in the chlorine contact chamber effluent at Jones Island. F+ coliphage was analyzed based on USEPA Methods 1601 and 1602.

Primary clarifier influent samples without pickle liquor yielded much higher concentrations of F+ coliphage than those with pickle liquor. The concentrations of F+ coliphage on July 6 when no pickle liquor was present were 1,372 and 1,424 PFU/mL. It appears that the presence of pickle liquor in the primary clarifier influent inhibited much of the F+ coliphage. It is possible that pickle liquor, or the iron in pickle liquor, has an inhibitory effect on F+ coliphage even at low concentrations. It is possible that viruses may be inhibited by the pickle liquor similarly to F+ coliphage. Without pickle liquor, the CEC units reduced the F+ coliphage concentration to less than 10 PFU/mL, while UV disinfection reduced concentrations even further to less than 1 PFU/mL and even below detection limits in some cases. This equates to about 2 to 3 log10 removal through CEC and about 4 log10 removal through CEC plus UV disinfection. Similar removal was observed through primary and secondary treatment followed by chloramine disinfection at South Shore, although the chloramine disinfection system never reduced F+ concentrations below 0.7 PFU/mL.

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There were not enough virus data collected to establish a correlation between F+ coliphage and virus levels in the chloraminated and UV disinfected effluent. On the basis of observed and anticipated virus and F+ coliphage removal by the treatment processes tested in this demonstration study, it appears that F+ coliphage provides a reasonable estimation of virus removal when pickle liquor is not present in the wastewater. However, viruses may be present even when the F+ coliphage concentration is 0 PFU/mL, as was the case on July 6.

Frequent monitoring for F+ coliphage may not be necessary in a full-scale system as long as the CEC and UV disinfection systems are functioning properly and are achieving their TSS, UVT and fecal coliform target levels. Simply monitoring parameters like TSS, turbidity and UVT levels across CEC and fecal coliform levels across UV disinfection should be adequate for ensuring the treatment processes are functioning properly and therefore the virus removal reported in literature and observed in this demonstration study can be expected.

Bacteroides spp. were also sampled and analyzed on July 6. The Bacteroides analysis included both conventional and real-time polymerase chain reaction (PCR) analysis. Conventional PCR analysis detected the presence of Bacteroides spp., whereas real-time PCR analysis quantified intact Bacteroides spp. cells (both dead and live). Since real-time PCR analysis quantifies both dead and live cells, it is not possible to compare chlorination and UV disinfection results. It is possible to compare removal efficiencies of Bacteroides spp. by CEC (coagulation). Intact Bacteroides spp. cells were present in all water samples, including primary clarifier influent, and CEC, UV, secondary clarifier, and chlorine contact chamber effluents. ACTIFLO showed a 1 log10 removal, whereas DensaDeg showed none. Because of the limited data set, Bacteroides spp. removal by CEC is inconclusive.

CONCLUSIONS The CEC demonstration testing at the South Shore WWTP provided a wealth of data that assisted the District in conceptual design evaluations of wet-weather treatment alternatives. The CEC processes provided high levels of treatment at very high overflow rates, minimizing their footprint for inclusion at either the Jones Island or South Shore WWTPs. Specific industrial wastewater components and process chemicals that are typically added to the wastewater may make the CEC process susceptible to reduced performance, and this must be considered in design of CEC facilities. When these factors are accounted for, CEC can achieve UVT levels acceptable for application of UV disinfection.

The following specific findings and conclusions can be made from the results of the demonstration study:

• Both CEC units exhibited excellent stability, achieved excellent TSS removal, and achieved good BOD5 removal (but higher that permit limits for BOD5) with either alum or ferric chloride.

• UV disinfection of CEC effluent was much more effective with alum coagulation rather than with ferric chloride.

• Reduction of E. coli and fecal coliform through the CEC units was similar to that achieved through primary and secondary treatment at South Shore.

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• Similar reduction of fecal coliform, E. coli, and F+ coliphage was achieved by UV disinfection of CEC effluent and by chlorine (chloramine) disinfection of secondary effluent at South Shore, as long as the CEC process reduced TSS levels to below 20 mg/L and the coagulant was alum.

• If chloramine disinfection is installed downstream of CEC, the recommended coagulant doses can be reduced when compared to UV disinfection. Either alum or ferric chloride will work with chlorine disinfection.

• The ferrous iron in the pickle liquor added to the influent of the CEC units can foul the UV lamp sleeves very quickly and lower the UV dose being applied to the CEC effluent.

• Because of the limited data set, Bacteroides spp. removal by CEC was inconclusive. Since real-time PCR analysis quantifies both dead and live cells, it was not possible to compare chlorination and UV disinfection results.

ACKNOWLEDGEMENTS The authors wish to acknowledge the contributions of the following: MMSD Laboratory (Sue Crowley, Jeff MacDonald, Sharon Mertens, Mike Neville), Great Lakes Water Institute (Sandra McLellan), University of Arizona (Chuck Gerba), Clancy Environmental Consultants, Inc. (Jennifer Clancy and Randi McCuin), Kruger, Inc., Infilco Degremont, Inc., and Trojan Technologies, Inc.

REFERENCES CH2M HILL. 1993. Tampa Water Resources Recovery Project Pilot Studies, Volume 1 Final Report.

Enriquez, Carlos. 1999. “Adenoviruses.” In Waterborne Pathogens, ed. David Talley. AWWA. pp. 223–26.

Gerba, C. P. 1999. “Enteroviruses.” In Waterborne Pathogens, ed. David Talley. AWWA. pp. 235–9.

Gerba, C. P., S. N. Singh, and J. B. Rose. 1985. “Waterborne Viral Gastroenteritis and Hepatitis.” CRC Crit. Rev. in Environmental Control 15: 213–36.

Gerba, C. P., J. B. Rose, and C. N. Haas. 1996. “Sensitive Population: Who Is at Greatest Risk?” International Journal of Food Microbiology. 30:113–23.

Letterman, R. D., ed. 1999. Water Quality and Treatment: A Handbook of Community Water Supplies (5th ed.). McGraw-Hill.

MacDonald, Jeff, MMSD Central Lab. N.d. Spreadsheet with internal MMSD Giardia data.

McLellan, S. June 2005 Telephone conversation with Sandra McLellan regarding the F+ coliphage.

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Nieuwstad, Th. J., A. H. Havelaar, and M. van Olphen. 1991. Hydraulic and Microbiological Characterization of Reactors for Ultraviolet Disinfection of Secondary Wastewater Effluent. Water Research. 25:775-783.

NRC. National Research Council. 1996. Use of Reclaimed Water and Sludge in Food Crop Production. Washington, D.C.: National Academy Press.

NRC. National Research Council. 1998. Issues in Potable Reuse. Washington, DC.

Rose, J. B., L. J. Dickson, S. R. Farrah, and R. P. Carnahan. 1996. “Removal of Pathogenic and Indicator Microorganisms by a Full-Scale Water Reclamation Facility.” Water Research 30:2785–97.

Rose, J. B., M. Robbins, D. Friedman, K. Riley, S. R. Farrah, and C. L. Hamann. 1997. “Evaluation of Microbiological Barriers at the Upper Occoquan Sewage Authority.” Pp. 291–305 in 1996 Water Reuse Conference Proceedings, February 25–28, San Diego, CA. Denver, CO: American Water Works Association.

Sedmak, G., et al. 2005. “Nine-Year Study of the Occurrence of Culturable Viruses in Source Water for Two Drinking Water Treatment Plants and the Influent and Effluent of a Wastewater Treatment Plant in Milwaukee, Wisconsin (August 1994 through July 2003).” Applied and Environmental Microbiology. 71:1042–50.

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Operating Chemically Enhanced Clarification for Optimum ...CEC processes were tested at the South Shore WWTP: DensaDeg®, manufactured by Infilco Degremont, and ACTIFLO®, manufactured