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ENVIRONMENT AGENCY

_________________________

SMART SPONGE®

LABORATORY TRIALS

_________________________

REPORT

October 2012

APEM REF: 412271

P/2015/01588ADDITIONAL 13/6/2016

APEM Scientific Report 412271

October 2012

ii

CLIENT: Amanna Rahman

ADDRESS: Environment Agency

Evidence Directorate

Cambria House

29 Newport Road

Cardiff

CF24 0TP

PROJECT No: 412271

DATE OF ISSUE: October 2012

PROJECT DIRECTOR: Dr David Fraser

PROJECT MANAGER: Dr Annemarie Clarke

REPORT AUTHORS: Dr Annemarie Clarke

APEM (2012) Smart Sponge®

laboratory trials. APEM Scientific Report 412271

APEM LTD

Riverview, A17 Embankment Business Park,

Heaton Mersey, Stockport SK4 3GN

Tel: 0161 442 8938 Fax: 0161432 6083

Registered in England No. 2530851

Website: www.apemltd.co.uk


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CONTENTS

CONTENTS ......................................................................................................................................... III

1 INTRODUCTION .......................................................................................................................... 1

1.1 SMART SPONGE BACKGROUND .................................................................................................. 1 1.2 ANTI-MICROBIAL AGENT ........................................................................................................... 1

2 EXPERIMENTAL DESIGN ......................................................................................................... 3

2.1 SOURCING ................................................................................................................................. 3 2.2 FLUME DESIGN .......................................................................................................................... 3 2.3 EXPERIMENTAL DESIGN ............................................................................................................. 6 2.4 BACKWASHING THE FLUMES ..................................................................................................... 9 2.5 STATISTICAL ANALYSIS ........................................................................................................... 10

3 RESULTS ...................................................................................................................................... 11

3.1 FLOW RATES DURING TEST EXPERIMENTS ................................................................................ 11 3.2 SUSPENDED SEDIMENT DURING TEST EXPERIMENTS ................................................................ 11 3.3 MICROBIOLOGICAL RESULTS – TEST EXPERIMENTS ................................................................. 12 3.4 FLOW RATE AND SUSPENDED SEDIMENT CONCENTRATION DURING FINE-SEDIMENT BLOCKING

EXPERIMENT ........................................................................................................................................ 16 3.5 MICROBIOLOGICAL RESULTS – FINE SEDIMENT BLOCKING ...................................................... 18 3.6 FLOW RATES DURING USED ENGINE OIL BLOCKING EXPERIMENT ............................................. 22 3.7 MICROBIOLOGICAL RESULTS – USED ENGINE OIL BLOCKING ................................................... 23 3.8 STATISTICAL ANALYSIS OF MICROBIOLOGICAL RESULTS ......................................................... 27 3.9 SUMMARY OF MICROBIOLOGICAL RESULTS ............................................................................. 29

4 DISCUSSION ................................................................................................................................ 30

4.1 FLOW RATE AND SUSPENDED SEDIMENT ADDITION.................................................................. 30 4.2 MICROBIOLOGICAL RESULTS ................................................................................................... 31

5 REFERENCES ............................................................................................................................. 33


October 2012

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EXECUTIVE SUMMARY

APEM Ltd was contracted by the Environment Agency to run a series of laboratory

trials on Smart Sponge® and Smart Sponge

® PLUS to provide independent results of

the efficiency of the product at removing faecal indicator organisms (FIOs) from

water. Smart Sponge®

was developed as an aid to the removal of hydrocarbons from

the aquatic environment during the response to the Exxon Valdez disaster of 1989.

Smart Sponge® PLUS was a later development which, in addition to hydrocarbon

removal, reduced the concentration of coliform bacteria through an anti-microbial

action provided by the bonding of organosaline quaternary amine to the Smart

Sponge® surface.

A side by side comparison of the effectiveness of Smart Sponge® and Smart

Sponge® PLUS treatment trains at removing E. coli, intestinal enterococci and the

coliphage MS2+ was carried out under the following test conditions:

1. Varying concentrations of FIOs and suspended solid concentrations;

2. Serial increase in fine suspended solids to assess performance as sponges

become blocked with sediment;

3. Serial increase in hydrocarbons to assess performance as sponges become

blocked with hydrocarbons.

The environmental water used in the experiments was collected from the Manchester

Ship Canal (MSC) downstream of the outfall of the Davyhulme Waste Water

Treatment Works thanks to the kind permission of United Utilities (UU) (the ‘dirty’

environmental water), or from within the Inner Basins at Salford Quays thanks to the

kind permission of Urban Vision (the ‘clean’ environmental water). This allowed use

of natural bacterial populations, considered to increase the realism of the laboratory

trials. The coliphage MS2+ and gully pot sediment was provided by the EA. Used

engine oil was used as the source of hydrocarbons.

Two Perspex flumes were custom built to house the Smart Sponge®

and Smart

Sponge® PLUS treatment packs. These were set to have an internal dimension of

300 mm square to securely house the sponges. The bottoms of the flumes were coated

with a silicon sealant and the SmartPacks were settled into this. This approach was

adopted to ensure that the experimental water did not run to the bottom of the flume

during transit and therefore by-pass the sponges, so contaminating the ‘downstream’

samples. A baffle was located upstream of the treatment pack to raise the water level,

ensuring that water entered the treatment train in the middle of the sponge units.

During the experiments where FIO concentration and suspended sediment loading

was varied E. coli concentrations were consistently reduced by 99 to 100% by the

Smart Sponge® PLUS flume, while the Smart Sponge

® flume was more variable and

recorded reductions between 2.4 and 82.3%, as well as a single increase of 15.4%.

A similar pattern was observed for Enterococci, with the Smart Sponge® PLUS flume

consistently reducing concentrations to <10 CFU/100 ml (99.8 to 99.9% reduction)

and the Smart Sponge® flume being more variable, with reductions of between 1.1

and 41.7% recorded as well as five occasions when concentrations increased in the

downstream samples (by between 11.1 and 112.1%).


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With regard to coliphage concentrations the same pattern of the Smart Sponge® PLUS

flume being more consistent than the Smart Sponge® flume was repeated. The Smart

Sponge® PLUS flume recorded reductions of between 84.5 and 100%, as well as a

single occurrence when phage concentration increased by 48%. The Smart Sponge®

flume recorded reductions of between 8.2 to 54.3%, as well as six occasions when

phage concentration increased (by between 3.9 and 184.6%).

The serial blocking with fine sediment experiments resulted in a flow rate decrease by

ca. four-fold for the Smart Sponge®

flume and ca. three-fold for the Smart Sponge®

PLUS flume. The Smart Sponge® PLUS flume was highly efficient and consistent at

reducing the concentration of E. coli and Enterococci with all results indicating a

reduction of between 97.7 and 99.9%, and no results indicating an increase. A

different pattern was apparent for the Smart Sponge® flume, where E. coli

concentration was reduced on only two occasions. In contrast, Enterococci showed a

decrease in concentration for every sample of between 74 and 99%, although removal

efficiency appeared to decrease as the experiment progressed.

Coliphage concentration varied between the flumes: Smart Sponge®

PLUS resulted in

a decrease in phage concentration for each sample, of between 84.5 and 100%. The

Smart Sponge® flume gave 50% of samples showing a decrease of between 6.7 and

91.5%, while the remaining 50% of samples showed an increase of between 0.5 and

101.8%.

During the hydrocarbon-blocking experiments the flow rate for each flume remained

relatively constant. The Smart Sponge® treatment train had a substantially higher flow

rate than the Smart Sponge® PLUS treatment train, which appeared to immediately be

slowed down by hydrocarbon addition. The Smart Sponge® PLUS flume consistently

and efficiently reduced the concentration of E. coli by between 99.7 and 100% (Table

3.11) and Enterococci by between 98.2 and 100%. The Smart Sponge® flume was

variable with regard to E. coli but for Enterococci all samples indicated a decrease in

concentration of between 1.1 and 87.9%. For coliphage, both flumes were variable

and reported both increases and decreases in concentration.

A statistically significant reduction in FIO concentration could be demonstrated

between Smart Sponge®

and Smart Sponge®

PLUS for both E. coli and Enterococci

(with Smart Sponge®

PLUS providing the greater reduction in FIO concentration)

while no significant difference could be demonstrated for Smart Sponge®.

The Smart Sponge® PLUS treatment pack demonstrated an attenuation (mean %

reduction) of -99.9% and -99.5% for E. coli and Enterococci respectively, with

confidence limits of 0.24% and 1.39% (respectively). This clearly demonstrates the

effectiveness of the antimicrobial agent. In contrast, while the Smart Sponge®

treatment train did result in an overall reduction for E. coli and Enterococci the mean

% reduction was much smaller (12 and 37.7% respectively), and less consistent.


October 2012

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1 INTRODUCTION

APEM Ltd were contracted by the Environment Agency to run a series of laboratory

trials on Smart Sponge® and Smart Sponge

® PLUS to provide independent results of

the efficiency of the product at removing faecal indicator organisms (FIOs) from

water. All other results currently available to date come from the USA where the

product was originally developed. The EA wished to test removal capability at FIO

concentrations up to 106 if possible, although a decision was taken to use a natural

source of contaminated water rather than spike a water source with a lab grown

pathogen to provide results indicative of a ‘real-world’ pathogen community. It was

considered that an environmental pathogen community may have been subject to

selective pressures, and would likely contain a wider range of microbiological strains.

The greater genetic diversity present in a natural community, as opposed to a

laboratory reference strain, was considered a better option to make the test more

realistic of field conditions.

The brief was to design an experimental set up to test the ability of the sponges to

remove FIOs from freshwater under a range of FIO concentrations, suspended

sediment concentrations as well as assessing any impact from hydrocarbon addition.

In particular, there was a requirement to observe if there was a significant difference

between the two sponge types in terms of reducing FIO concentrations, as there was a

consideration that if the FIOs were attached to suspended sediment particles then they

may be reduced by the Smart Sponge® if that was able to remove sufficient suspended

sediment from the water.

1.1 Smart Sponge background

Smart Sponge® and Smart Sponge

® PLUS were originally developed in the USA.

Smart Sponge®

was developed as an aid to the removal of hydrocarbons from the

aquatic environment during the response to the Exxon Valdez disaster of 1989.

Smart Sponge® PLUS was a later development which, in addition to hydrocarbon

removal, reduced the concentration of coliform bacteria. The anti-microbial

mechanism, based on the electromagnetic interaction with the cell membrane of

micro-organisms is claimed to be bound permanently to the polymer surface, and to

not diminish with time. Test results from the USA indicated that a filter bed depth of

>0.9m (i.e. a treatment train 0.9 m in length composed of Smart Sponge® PLUS) was

able to provide a >90% reduction in faecal coliforms when present at <103

CFU/100ml and a >90% reduction in Enterococcus when present at <104 CFU/100ml.

While a filter bed depth of >1.5 m was able to provide a >90% reduction in E.coli

when present at <103 CFU/100ml and a >90% reduction in total coliforms when

present at <104 CFU/100ml.

1.2 Anti-microbial agent

The anti-microbial agent used in Smart Sponge® PLUS is an organosilane quaternary

amine (CAD 27688-52-6). This antimicrobial protectant bonds chemically to a treated

surface by way of an extremely effective silane bonding agent, and provides the

permanent bond to the target surface (Smart Sponge® in this instance). The quaternary


October 2012

2

amine punctures the cell membranes of microbes that come into contact with the

treated surface, and the subsequent electrical charge shocks the cell. The antimicrobial

does not lose its strength as nothing is transferred to the microbes during the

destruction of the cells1. The company website (XMicrobes) from which this

information comes notes that in order for the protectant to continue its effectiveness,

‘normal cleaning of treated surfaces is necessary’, and that dirt build-up that covers

the treatment would prohibit it from killing microorganisms on contact.

1 http://xmicrobes.com/chemistry.html Last accessed 08/10/2012


October 2012

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2 EXPERIMENTAL DESIGN

2.1 Sourcing

The Smart Sponge® and Smart Sponge

® PLUS packs used to create the treatment

trains in the experiments reported here were provided to APEM Ltd by SmartSponge

Products Ltd on behalf of the EA. In total 12 Smart Sponge® ‘SmartPacks’ and 12

Smart Sponge® PLUS ‘SmartPacks’ were provided. Each individual SmartPack was

300 mm square and had a depth of 75 mm. SmartSponge Products Ltd advised that a

treatment train of at least 0.9 m would be required to achieve FIO reduction at the

concentrations proposed by the EA, and that therefore the 12 packs would be required

to create a treatment train of 0.9 m length. Advice was also given to ensure that the

experimental water entered the treatment train at the top or middle, to ensure it had

sufficient flow through the sponges to produce optimal results.

The environmental water used in the experiments was collected from the Manchester

Ship Canal (MSC) downstream of the outfall of the Davyhulme Waste Water

Treatment Works thanks to the kind permission of United Utilities (UU) (the ‘dirty’

environmental water), or from within the Inner Basins at Salford Quays thanks to the

kind permission of Urban Vision (the ‘clean’ environmental water). Water from the

MSC frequently has very high concentrations of FIOs, while the water from Salford

Quays is typically of bathing water quality. This combination of two different

environmental waters allowed the concentration of FIOs to be varied, by creating

serial dilutions of MSC water with the Salford Quays water. It is to be noted,

however, that this resulted in actual contamination concentrations being unknown

during experiments and allowed for the possibility of highly variable initial FIO

concentrations due to natural variation in the environmental water. While the FIO

concentration of the ‘clean’ environmental water was not directly tested during this

experiment, Salford Quays was monitored at locations on a fortnightly basis for FIOs

as part of on-going monitoring (APEM, unpublished data). Samples collected on July

23rd

and August 6th

2012 encompass the period when experimental water was

collected. Results from both sampling occasions indicate total coliforms at a

concentration <1,000 cfu/100 ml at all sites and faecal coliforms (e.g. E. coli) at

< 500 cfu/100 ml at all sites.

The EA also supplied a 10 ml vial of the coliphage MS2+ (at 1012

ml) and some tubs

of gully pot sediment which were used to make various combinations of experimental

test water. The coliphage was supplied as a glycerol solution, and was kept in the

freezer to maintain the coliphage in good state. The solution was well mixed before

each use. A supply of used engine oil was obtained from a nearby garage. See Section

2.3 for further details of experimental runs.

2.2 Flume design

The experimental design was based on a single ‘upstream’ water source (the

parameters of which could be varied between experiments) located in a 300 l capacity

water butt (see Figure 2.1). Two Perspex flumes were custom built to house the Smart

Sponge® and Smart Sponge

® PLUS treatment packs (see Figure 2.2 and Figure 2.3).

These were set to have an internal dimension of 300 mm square to securely house the


October 2012

4

sponges. The bottoms of the flumes were coated with a silicon sealant and the

SmartPacks were settled into this. This approach was adopted to ensure that the

experimental water did not run to the bottom of the flume during transit and therefore

by-pass the sponges, so contaminating the ‘downstream’ samples. A baffle was

located upstream of the treatment pack to raise the water level, ensuring that water

entered the treatment train in the middle of the sponge units (Figure 2.4).

Figure 2.1 Design of the 'upstream' water source for the flume experiments


October 2012

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Figure 2.2 The Smart Sponge

® flume.

Figure 2.3 The Smart Sponge

® PLUS flume

One flume had a treatment train composed solely of 12 ‘Smartpacks’ of Smart

Sponge®, while the other had a treatment train composed solely of 12 ‘Smartpacks’ of

Smart Sponge® PLUS. At the end of each flume smaller, 150 l capacity containers,

with volume gradations marked on the outside, were used to collect the treated water.


October 2012

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A submerged dirty water pump was used to pump water from the upstream water butt

and through both flumes. An overspill arrangement was used to control the volume of

water entering the flumes with excess water returning to the upstream water butt.

A test run was conducted using clean environmental water prior to any experimental

runs, and used to obtain a flow rate for the clean treatment trains.

Figure 2.4 Illustration of baffle before the treatment train

2.3 Experimental design

A series of seven experiments were run using a variety of combinations of ‘dirty’ and

‘clean’ environmental water, suspended sediment additions, fine sediment additions

and used engine oil to vary the make-up of the contaminated water run through the

sponges. Two main different types of experiments were run. A series of five ‘test’

experiments designed to test the ability of Smart Sponge® and Smart Sponge

® PLUS

to remove FIOs under a range of environmental conditions, and two ‘end-of-life’

experiments, where efforts were made to block the treatment trains with (a) fine

sediment and (b) used engine oil in order to assess any effect this may have had on

performance. In summary, a side by side comparison of Smart Sponge®

and Smart

Sponge® PLUS treatment trains was carried out under the following test conditions:

1. Varying concentrations of FIOs and suspended solid concentrations;

2. Serial increase in fine suspended solids to assess performance as sponges

become blocked with sediment;

3. Serial increase in hydrocarbons to assess performance as sponges become

blocked with hydrocarbons.


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2.3.1 Test experiments

The initial intent had been to carry out the ‘test’ experiments using a high suspended

sediment burden of ca. 1000 mg/l, and the first experiment run used this

concentration. This, however, resulted in the blocking of the Smart Sponge® flume,

and as a consequence a decision was made to run the test experiments with a nominal

50 mg/l added suspended sediment instead, following confirmation from the suppliers

of Smart Sponge®, that field installation would incorporate a measure to prevent

blocking of the treatment packs with suspended sediments (see Table 2.1).

Table 2.1 Composition of the experimental water for the first five ‘test’

experiments.*Experiment 7 was actually the first experiment run, but was re-

coded to 7 following the alteration to minimal suspended solid additions. Experiment

code

Canal

Water

Volume (l)

Salford

Quays

Water

Volume

(l)

Total

water

volume (l)

Suspended

sediment

concentration

(mg/l)

Added

sediment

(g)

Phage

addition

(ml)

1 300 0 300 50 15 1

2 150 150 300 50 15 1

3 75 225 300 50 15 1

4 300 0 300 100 30 1

7*

300 0 300 1000 300 1

2.3.1.1 Experimental protocol for ‘test’ experiments

Sufficient volumes of environmental water were collected each morning for one or

two experiments, and on return to the laboratory the 300 l of ‘upstream’ dirty water

was created for each experiment by adding the required volume of canal and quays

water, weighing in the appropriate amount of gully pot sediment and adding 1 ml of

well-mixed coliphage solution from the stock kept in the freezer.

Three paired samples (upstream and downstream Smart Sponge® flume and upstream

and downstream Smart Sponge® PLUS flume) for analysis of FIOs (E. coli,

Enterococci (CFU/100ml) and Phage (PFU/100ml)) were collected over the duration

of the experiment. Paired samples were collected at intervals based on the volume of

water that had passed through the flume (e.g. ‘0’ at the beginning of the experiment,

‘75’ and ‘100’) with the time of sample collection from the beginning of the

experiment noted to allow calculation of flow rate data. Samples for microbiological

analysis were collected from the water exiting the flume, and kept cool while being

stored prior to transport. Samples for the analysis of suspended sediment

concentration were also collected, being a single upstream sample at the beginning of

the experiment and a single downstream sample from each flume at the end of the

experiment. Downstream suspended sediment samples were collected from the

containers located at the end of the flumes, with the water being mixed before

sampling to prevent settling of any sediment that passed through the flumes.

Microbiological samples were kept in a cool box and sent by overnight courier to the

National Laboratory Service Starcross laboratory for analysis of E. coli (via TBX),

intestinal enterococci (via MEA) and MS2 coliphage (via TYGA). Suspended

sediment samples were analysed by filtration in house by APEM.


October 2012

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At the end of each experiment a small amount of household bleach (ca. 10 ml) was

added to each downstream container to deactivate the phage and the used

experimental water was poured away to waste via a drain connecting to the sewerage

system. At no point did water containing bleach enter the experimental flumes, or the

water butt used to hold the upstream experimental water. Similarly, at no point was

tap water (i.e. chlorinated water) used within the experimental set-up.

2.3.2 End-of-life experiments

Two ‘end-of-life’ experiments were run, using either sediment or used engine oil in

attempts to block the flumes. These experiments differed in that only 100 l of

experimental water was created, with ca. 30 l of water running through each flume.

Two samples for each flume (one upstream and one downstream) were collected at

start and end of each run.

The initial blocking of the flumes resulted in a change to the sediment-based ‘end-of-

life’ experiment, in that a decision was made to attempt to block the treatment packs

with fine sediment (as passed through a 150 µm sieve) as it was considered that there

was the possibility that fine sediments might still be able to enter the treatment packs

when installed in the field.

To obtain the fine sediment, the remaining gully pot sediment was washed through a

150 µm sieve using environmental water from Salford Quays. Three litres of water

containing the fine sediment were collected (referred to as ‘sediment solution’). The

concentration of suspended fine sediment was calculated to be 55 g per litre (based on

the difference in weight between 1 l each of quays water and sediment solution), and

from this, that the addition of 250 ml of sediment solution would add ca. 13.75 g of

fine sediment.

2.3.2.1 Experimental protocol – fine sediment blocking experiment

At the beginning of the day 400 l of canal water and 500 l of quays water was

collected. A control experiment was run using 100 l of quays water to provide initial

timings through the flumes for 30 l per flume. A series of eight ‘runs’ were made to

progressively block the sponges, with samples for analysis collected on alternate runs

(i.e. on four occasions) as shown in Table 2.2.

An addition of 250 ml of sediment solution was made to 100 l of quays water (‘clean’

environmental water) and this was run through the flumes to provide a ‘clog’ run. An

experimental run was then conducted where 250 ml of sediment solution was added to

100 l of canal water (‘dirty’ environmental water), and 1 ml of well mixed coliphage

solution was added. This experimental water was then run through the flumes and

paired upstream and downstream samples were collected for each flume at the

beginning and end of the run. This process of having a ‘clogging’ run of sediment and

‘clean’ environmental water followed by an experimental run of sediment, ‘dirty’

environmental water and coliphage was then repeated a further three times. On the

third and fourth runs, the volume of sediment solution added to both clog runs and

experimental runs was increased to 500 ml (ca. 27.5 g sediment). See Table 2.2 for

schedule of clogging runs and experimental runs.


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Table 2.2 Fine sediment blocking experiment strategy Experiment

code

Canal

Water

Volume (l)

Salford

Quays

Water

Volume

(l)

Sediment

solution

added

(ml)

Accumulated

sediment (g)

Phage

addition (ml)

Samples

collected

for

analysis

5 – clog 0 100 250 13.75 0

5 100 0 250 27.5 1 Yes

6 – clog 0 100 250 41.25 0

6 100 0 250 55 1 Yes

8 - clog 0 100 500 82.5 0

8 100 0 500 110 1 Yes

9 – clog 0 100 500 137.5 0

9 100 0 500 165 1 Yes

Sample collection and test water disposal followed the same protocol as for the test

experiments.

2.3.2.2 Experimental protocol – used engine oil blocking experiment

These experiments followed the same approach as that used for the fine-sediment

blocking runs, with additions of engine oil made using ‘clean’ environmental water to

increase the amount added between experimental runs using ‘dirty’ environmental

water. The used engine oil was added to the water once it was in the flume as it was

not possible to agitate the water sufficiently in the upstream water butt to create an

emulsion. An initial clog run was not used however, and a decision was made to treble

the amount added for the last three runs (see Table 2.3). No suspended sediment

additions were made during this experiment.

Table 2.3 Used engine oil blocking strategy Experiment

code

Canal

Water

Volume (l)

Salford

Quays

Water

Volume

(l)

Hydrocarbon

addition (g)

Accumulated

hydrocarbon

(g)

Phage

addition

(ml)

Samples

collected

for

analysis

10 100 0 40 40 1 Yes

11 – clog 0 100 40 80 0

11 100 0 40 120 1 Yes

12 - clog 0 100 40 160 0

12 100 0 120 280 1 Yes

13 – clog 0 100 120 400 0

13 100 0 120 520 1 Yes

Sample collection and test water disposal was the same as for the test experiments.

2.4 Backwashing the flumes

After the flumes became blocked during the first attempted experiment it was

necessary to ‘back-wash’ them in order to re-use them. This was accomplished by

reversing the flumes and rinsing through with clean environmental water. Water and

sediment washed out of the flumes during this process was discarded. Occasional

backwashes were used throughout the trials.


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After the initial experiment, and before experiment 1.

Before experiment 3

Before experiment 5

Before experiment 10

The backwash protocol was designed to improve flow rate only, and was not used to

clear the flumes of FIOs or phage. Once the flumes had been used (i.e. after the initial

test of the system with clean environmental water), the presence of a residual FIO

community in the flumes is a possibility. After the first experiment, the presence of a

residual phage and FIO community in the flumes is a possibility.

2.5 Statistical analysis

To test the efficiency of the sponges in removing FIOs the difference in concentration

between upstream and downstream samples for both Smart Sponge® and Smart

Sponge® PLUS was calculated for E. coli, Enterococci and coliphage. This data was

then combined, tested for normality (Shapiro & Wilk, 1965), and log10 transformed

where appropriate. A t-test (assuming unequal variances) was then used at the one-

tailed level to determine if there was a significant difference between the two types of

sponge. A one-tailed test was considered appropriate because a difference between


® PLUS was expected.


October 2012

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3 RESULTS

3.1 Flow rates during test experiments

Table 3.1 Calculated flow rates based on time and total volume per flume during

test experiments

Experiment Smart Sponge® Smart Sponge® PLUS

Dirty

water

(1)

Clean

water

(l)

Upstream

suspended

solids

(mg/l)

Time

(mins)

Volume

(l)

Flow

rate

(l/s)

Time

(mins)

Volume

(l)

Flow

rate

(l/s)

Test 0 100 n/a 4.17 100 0.4 5.74 100 0.29

1 300 0 25.04 19.73 122.5 0.19 22.95 90.75 0.066

2 150 150 30.02 35.12 96.5 0.046 10.85 104.5 0.16

3 75 225 30.08 18.32 99 0.09 11.57 100 0.14

4 300 0 63.10 19.33 84 0.072 27.25 104 0.064

7 300 0 800.38 70.00 64 0.015 70 90 0.021

Blocking of the flumes during experiment 7 resulted in the experiment being

abandoned after 1 hr and 10 mins to ensure that samples were delivered in time for the

courier. As a consequence only two samples for microbiological analysis were

collected for the Smart Sponge flume, with the final volume being only 64 l.

The test run on clean sponges (run with clean environmental water from Salford

Quays) gave similar flow rates for both flumes, with the Smart Sponge® PLUS flume

being slightly slower than the Smart Sponge®

flume. The initial experiment (7)

resulted in very slow flow rates, as would be expected following the observed

blocking. Experiments 1 to 4 showed a general trend of decreasing flow rates (as

would be expected given likelihood of flume blocking with sediment). The backwash

before Experiment 1 and Experiment 3 resulted in an increase in flow rate for both

flumes for Experiment 1, but only Smart Sponge® for Experiment 3.

3.2 Suspended sediment during test experiments

Table 3.2 Suspended sediment measurements from the test experiments

Experiment Upstream

(mg/l)

Smart Sponge®

(mg/l)

Smart Sponge® PLUS

(mg/l)

1 25.04 0.004 0.004

2 30.02 0.0023 0.0015

3 30.08 0.0045 0.0042

4 63.10 0.0045 0.0045

7 800.38 - -

Downstream suspended sediment samples were unfortunately not collected during the

initial experiment (Experiment 7). Visual observations, however, would suggest that

suspended sediment concentrations in the downstream containers would have been

higher than in the following experiments as a distinct colouration of the water was

observed.


October 2012

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Results from Experiments 1 to 4 (inclusive) indicate that both flumes were very

efficient at removing suspended sediments.

3.3 Microbiological results – test experiments

Microbiological results for the test experiments are shown for E. coli, Enterococci and

phage respectively in Tables 3.3 to 3.6.

It can be seen that during Experiments 1 to 4 (inclusive) E. coli concentrations were

consistently reduced by 99 to 100% by the Smart Sponge®

PLUS flume, while the

Smart Sponge® flume was more variable and recorded reductions between 2.4 and

82.3%, as well as a single increase of 15.4% (Table 3.3).

A similar pattern was observed for Enterococci (Table 3.4), with the Smart Sponge®

PLUS flume consistently reducing concentrations to <10 CFU/100 ml (99.8 to 99.9%

reduction) and the Smart Sponge®

flume being more variable, but less effective than

for E. coli, with reductions of between 1.1 and 41.7% recorded as well as five

occasions when concentrations increased in the downstream samples (by between

11.1 and 112.1%).

With regard to phage concentrations (Table 3.5) the same pattern of the Smart

Sponge® PLUS flume being more consistent than the Smart Sponge

® flume is again

repeated. The Smart Sponge® PLUS flume recorded reductions of between 84.5 and

100%, as well as a single occurrence when phage concentration increased by 48%.

The Smart Sponge® flume recorded reductions of between 8.2 to 54.3%, as well as six

occasions when phage concentration increased (by between 3.9 and 184.6%).


October 2012

13

Table 3.3 Results for E. coli (cfu/100 ml) from the 'test' experiments. Note values written in red text highlight where increases in

concentration have occurred downstream. The upstream suspended solids load for each experiment is provided beneath the Experiment

number. Smart

Sponge Smart

Sponge plus

Experiment Volume (l) Upstream Downstream Change Upstream Downstream Change Change

1 0 22,000 3,700 -83.2% 14,000 <10 >4 log -99.9% 25 mg/l 75 29,000 8,364 -71.2% 21,000 <10 >4 log -100.0% 100 17,000 7,200 -57.6% 14,000 <10 >4 log -99.9% 2 0 13,000 2,200 -83.1% 7,200 <10 >3 log -99.9% 30 mg/l 75 6,900 5,500 -20.3% 6,400 <10 >3 log -99.8% 100 6,500 7,500 +15.4% 17,000 <10 >4 log -99.9% 3 0 43,000 22,000 -48.8% 46,000 <10 >4 log -100.0% 30 mg/l 75 50,000 19,000 -62.0% 56,000 <10 >4 log -100.0% 100 58,000 24,000 -58.6% 48,000 <10 >4 log -100.0% 4 0 53,000 50,000 -5.7% 52,000 <10 >4 log -100.0% 63 mg/l 75 42,000 41,000 -2.4% 50,000 240 >4 log -99.5% 100 56,000 42,000 -25.0% 53,000 216 >4 log -99.6% 7 0 1,727 2,100 +21.6% 3,000 6,900 +130.0% 800 mg/l 50 3,200 3,300 +3.1% 2,100 <10 >3 log -99.5%

90 2,700 <10 >3 log -99.6%

Mean % change (including Experiment 7) -34.1 -84.5 Mean % change (excluding Experiment 7)

-41.9 -99.9


October 2012

14

Table 3.4 Results for Enterococci (cfu/100 ml) from the 'test' experiments. Note values written in red text highlight where increases in

concentration have occurred downstream. The upstream suspended solids load for each experiment is provided beneath the Experiment

number. Smart

Sponge Smart

Sponge plus


1 0 14,000 12,000 -14.3% 7,000 <10 >3 log -99.9% 25 mg/l 75 9,000 7,000 -22.2% 6,000 <10 >3 log -99.8% 100 7,000 11,000 +57.1% 4,600 <10 >3 log -99.8% 2 0 5,200 3,200 -38.5% 12,000 <10 >4 log -99.9% 30 mg/l 75 9,000 7,000 -22.2% 5,000 <10 >3 log -99.8% 100 12,000 7,000 -41.7% 6,000 <10 >3 log -99.8% 3 0 9,000 7,800 -13.3% 9,091 <10 >3 log -99.9% 30 mg/l 75 6,000 13,000 +116.7% 10,000 <10 >4 log -99.9% 100 8,182 9,091 +11.1% 11,000 <10 >4 log -99.9% 4 0 8,000 9,000 +12.5% 9,000 <10 >3 log -99.9% 63 mg/l 75 8,000 7,909 -1.1% 7,600 <10 >3 log -99.9% 100 6,600 14,000 +112.1% 7,800 <10 >3 log -99.9% 7 0 12,000 7,000 -41.7% 8,000 <10 >3 log -99.9% 800 mg/l 50 21,000 13,000 -38.1% 10,000 <10 >4 log -99.9%

90 13,000 <10 >4 log -99.9%

Mean % change (including Experiment 7) +5.5 -99.9 Mean % change (excluding Experiment 7) +13.0 -99.9


October 2012

15

Table 3.5 MS2 coliphage (pfu/100 ml) results from the 'test' experiments. Note values written in red text highlight where increases in

concentration have occurred downstream The upstream suspended solids load for each experiment is provided beneath the Experiment

number. Smart

Sponge Smart

Sponge plus


1 0 45,000,000 48,000,000 +6.7% 18,000,000 74,000 >3 log -99.6% 25 mg/l 75 116,000,000 68,000,000 -41.4% 65,000,000 90 >6 log -100.0% 100 76,000,000 79,000,000 +3.9% 86,000,000 90 >6 log -99.99% 2 0 94,000,000 102,000,000 +8.5% 164,000,000 31,000 >4 log -99.98% 30 mg/l 75 128,000,000 143,000,000 +11.7% 89,000,000 4,700 >5 log -99.99% 100 127,000,000 103,000,000 -18.9% 115,000,000 180 >6 log -99.99% 3 0 127,000,000 58,000,000 -54.3% 42,000,000 6,500,000 >1 log -84.5% 30 mg/l 75 85,000,000 117,000,000 +37.6% 25,000,000 37,000,000 +48.0% 100 130,000,000 100,000,000 -23.1% 75,000,000 6,800,000 >2 log -90.9% 4 0 114,000,000 96,000,000 -15.8% 3,700,000 35,000 >3 log -99.1% 63 mg/l 75 97,000,000 89,000,000 -8.2% 7,000,000 205,000 >2 log -97.1% 100 39,000,000 111,000,000 +184.6% 55,000,000 57,000 >3 log -99.9% 7 0 95,000,000 61,000,000 -35.8% 175,000,000 4,100,000 >2 log -97.7% 800 mg/l 50 238,000,000 175,000,000 -26.5% 209,000,000 240,000 >3 log -99.9%

90 90,000,000 58,000 >4 log -99.9% Mean % change (including Experiment 7) +2.1

-88.0

Mean % change (excluding Experiment 7) +7.6

-85.3


October 2012

16

3.4 Flow rate and suspended sediment concentration during fine-sediment

blocking experiment

The results (Table 3.6) indicate that flow rate decreases over the duration of the

experiments, by ca. four-fold for the Smart Sponge®

flume and ca. three-fold for the

Smart Sponge® PLUS flume. Figure 3.1 indicates that the reduction in flow rate was

very similar for both flumes. The results suggest that both flumes were very efficient

at retaining fine sediment.


October 2012

17

Table 3.6 Results from the fine-sediment blocking experiment

Smart Sponge® Smart Sponge® PLUS

Experiment Added

sediment

solution

(ml)

Expected

accumulated

sediment (g)

Measured

U/S

sediment

(g)

Measured

D/S

sediment

(g)

Time

(mins)

Volume

(l)

Flow

rate

(l/s)

Measured

D/S

sediment

(g)

Time

(mins)

Volume

(l)

Flow

rate

(l/s)

Control 2.8 30 0.18 3.5 30 0.14

5 – clog 250 13.75 2.8 30 0.18 3.5 30 0.14

5 250 27.5 7.8 0.006 3.8 30 0.13 0.005 3.3 30 0.15

6 – clog 250 41.25 5.8 30 0.087 5.6 30 0.089

6 250 55 7.0 0.005 5.9 30 0.085 0.006 6.7 30 0.075

8 – clog 500 82.5 6.6 30 0.076 6.5 30 0.078

8 500 110 13.4 0.006 7.3 30 0.069 0.007 7.2 30 0.069

9 – clog 500 137.5 9.1 30 0.055 9.3 30 0.054

9 500 165 14.1 0.005 11.6 30 0.043 0.005 11.3 30 0.044


October 2012

18

Figure 3.1 Change in flow rate for the flumes during blocking with fine-

sediments

3.5 Microbiological results – fine sediment blocking

Microbiological results for the fine-sediment blocking experiment are shown for E.

coli, Enterococci and phage respectively in Tables 3.7 to 3.9.

It can be seen that the Smart Sponge®

PLUS flume is highly efficient and consistent at

reducing the concentration of E. coli and Enterococci (Table 3.7 and Table 3.8

respectively), with all results indicating a reduction of between 97.7 and 99.9%, and

no results indicating an increase. A different pattern is apparent for the Smart

Sponge® flume. With regard to E. coli (Table 3.7) it is apparent that a reduction in

concentration occurred on only two occasions, with most samples indicating an

increase in concentration of between 7.4 and 150%. In contrast, Enterococci results

(Table 3.8) indicated a decrease in concentration for every sample of between 74 and

99%, although removal efficiency appears to decrease as the experiments progress.

The results for phage vary between the flumes (Table 3.9). Smart Sponge® PLUS

resulted in a decrease in phage concentration for each sample, of between 84.5 and

100%. The Smart Sponge® flume gave 50% of samples showing a decrease of

between 6.7 and 91.5%, while the remaining 50% of samples showed an increase of

between 0.5 and 101.8%.


October 2012

19

Table 3.7 Results for E. coli (cfu/100 ml) from the fine-sediment blocking experiment. Note values written in red text highlight where

increases in concentration have occurred downstream. Expected accumulated sediment (g) is shown below the Experiment number. Smart

Sponge Smart

Sponge plus


5 0 8,000 20,000 +150.0% 18,000 <10 >4 log -99.9% 27.5 30 21,000 17,000 -19.0% 15,000 <10 >4 log -99.9% 6 0 21,000 23,000 +9.5% 14,000 <10 >4 log -99.9% 55 30 12,000 16,000 +33.3% 15,000 <10 >4 log -99.9% 8 0 9,000 12,000 +33.3% 12,000 27 >4 log -99.8% 110 30 14,000 15,000 +7.1% 11,000 <10 >4 log -99.9% 9 0 13,000 15,000 +15.4% 12,000 27 >4 log -99.8% 165 30 20,000 11,000 -45.0% 14,000 <10 >4 log -99.9%

Mean % change +23.1 -99.9


October 2012

20

Table 3.8 Results for Enterococci (cfu/100 ml) from the fine-sediment blocking experiment. Note values written in red text highlight

where increases in concentration have occurred downstream. Expected accumulated sediment (g) is shown below the Experiment

number. Smart

Sponge Smart

Sponge plus


5 0 610 54 -91.1% 580 <10 >2 log -98.3% 27.5 30 570 72 -87.4% 440 <10 >2 log -97.7% 6 0 892 <10 -98.9% 750 <10 >2 log -98.7% 55 30 991 <10 -99.0% 680 <10 >2 log -98.5% 8 0 3,000 780 -74.0% 4,600 <10 >3 log -99.8% 110 30 4,200 650 -84.5% 5,400 <10 >3 log -99.8% 9 0 19,000 4,000 -78.9% 17,000 <10 >4 log -99.9% 165 30 20,000 2,800 -86.0% 12,000 <10 >4 log -99.9%

Mean % change -87.5 -99.1


October 2012

21

Table 3.9 Results for MS2 coliphage (pfu/100 ml) from the fine-sediment blocking experiment. Note values written in red text highlight

where increases in concentration have occurred downstream. Smart

Sponge Smart

Sponge plus


5 0 109,000,000 220,000,000 +101.8% 72,000,000 4,400 >5 log -100.0% 27.5 30 282,000,000 263,000,000 -6.7% 61,000,000 49,000 >4 log -99.9% 6 0 104,000,000 173,000,000 +66.3% 81,000,000 510,000 >3 log -99.4% 55 30 366,000,000 31,000,000 -91.5% 342,000,000 1,040,000 >3 log -99.7% 8 0 221,000,000 145,000,000 -34.4% 224,000,000 22,900,000 >1 log -89.8% 110 30 211,000,000 212,000,000 +0.5% 193,000,000 16,100,000 >2 log -91.7% 9 0 349,000,000 257,000,000 -26.4% 304,000,000 41,000,000 >1 log -86.5% 165 30 247,000,000 333,000,000 +34.8% 297,000,000 46,000,000 >1 log -84.5%

Mean % change +5.6 -93.9


October 2012

22

3.6 Flow rates during used engine oil blocking experiment

Table 3.10 Flow rates from the flumes during the used engine oil blocking

experiment

Smart Sponge Smart Sponge PLUS

Experiment Time (s) Volume

(l)

Flow

rate (l/s)

Time (s) Volume

(l)

Flow

rate (l/s)

10 235 30 0.13 873 30 0.034

11 212 30 0.13 749 30 0.040

12 187 30 0.16 731 30 0.041

13 221 30 0.14 728 30 0.041

The results indicate that the flow rate for each flume remains relatively constant

during the attempt to block the sponges, but that the Smart Sponge® treatment train

has a substantially higher flow rate than the Smart Sponge® PLUS treatment train,

which appears to immediately be slowed down by hydrocarbon addition.

Figure 3.2 Change in flow rate for the flumes during the used engine oil blocking

experiment


October 2012

23

3.7 Microbiological results – used engine oil blocking

Microbiological results for the used engine oil blocking experiment are shown for E.

coli, Enterococci and phage respectively in Tables 3.11 to 3.13.

The results indicate that the Smart Sponge® PLUS flume consistently and efficiently

reduced the concentration of E. coli by between 99.7 and 100% (Table 3.11) and

Enterococci by between 98.2 and 100% (Table 3.12).


October 2012

24

Table 3.11 Results for E. coli (cfu/100 ml) from used engine oil blocking experiment. Note values written in red text highlight where

increases in concentration have occurred downstream. Smart

Sponge Smart

Sponge plus

Experiment Volume Upstream Downstream Change Upstream Downstream Change Change

10 0 24,000 13,000 -45.8% 26,000 <10 >4 log -100.0% 30 15,000 13,000 -13.3% 16,000 54 >4 log -99.7% 11 0 28,000 30,000 +7.1% 40,000 <10 >4 log -100.0% 30 37,000 29,000 -21.6% 28,000 <10 >4 log -100.0% 12 0 16,000 28,000 +75.0% 22,000 <10 >4 log -100.0% 30 23,000 23,000 0.0% 26,000 18 >4 log -99.9% 13 0 16,000 16,000 0.0% 14,000 <10 >4 log -99.9% 30 26,000 21,000 -19.2% 19,000 <10 >4 log -99.9%

% change -2.2 -99.9


October 2012

25

Table 3.12 Results for Enterococci (cfu/100 ml) from used engine oil blocking experiment. Note values written in red text highlight

where increases in concentration have occurred downstream. Smart

Sponge Smart

Sponge plus


10 0 9,909 3,600 -63.7% 16,000 <10 >4 log -99.9% 30 10,000 2,400 -76.0% 9,455 <10 >3 log -99.9% 11 0 8,818 3,000 -66.0% 4,000 <10 >3 log -99.8% 30 14,000 2,400 -82.9% 12,000 <10 >4 log -99.9% 12 0 11,000 3,600 -67.3% 21,000 <10 >4 log -100.0% 30 15,000 4,800 -68.0% 17,000 <10 >4 log -99.9% 13 0 182 180 -1.1% 545 <10 >2 log -98.2% 30 892 108 -87.9% 546 <10 >2 log -98.2%

% change -64.1 -99.5


October 2012

26

Table 3.13 Results for MS2 coliphage (pfu/100 ml) from the used engine oil blocking experiment. Note values written in red text

highlight where increases in concentration have occurred downstream. Hydrocarbon addition (g) and accumulated hydrocarbons (g)

are shown below each Experiment number. Smart

Sponge Smart

Sponge plus


10 0 3,300,000 n/a 1,000,000 72,072 >2 log -92.8% 40/40 30 n/a 930,000 108,108 26,000 >1 log -75.9% 11 0 5,300,000 6,600,000 +24.5% 5,000,000 48,000 >3 log -99.0% 40/120 30 10,909,091 7,272,727 -33.3% 21,000,000 220,000 >2 log -99.0% 12 0 44,000,000 45,005 -99.9% 390,000 181,818 >1 log -53.4% 120/280 30 n/a 20,000,000 10,100,000 390,000 >2 log -96.1% 13 0 600,000 5,200,000 +766.7% 1,600,000 99,099 >3 log -93.8% 120/520 30 13,500 980,000 +7159.3% 16,000 168,000 +950.0%

% change +1563,4 +42.5


October 2012

27

A different pattern is apparent for the Smart Sponge® flume, where for E. coli four

samples indicate a decrease in concentration of between 13.3 and 45.8%, two samples

show no change and two samples indicate an increase in concentration of between 7.1

and 75%. For Enterococci all samples indicated a decrease in concentration of

between 1.1 and 87.9%.

For phage, three Smart Sponge® samples had un-reported concentrations, of those

samples with results two indicated a reduction in phage concentration of between 33.3

and 99.9%, while three reported an increase in concentration of between 24.5 and

7,159.3%. For the Smart Sponge® PLUS flume, seven of the samples reported a

decrease in phage concentration of between 53.4 and 99%, while one sample

indicated an increase of 950%.

3.8 Statistical analysis of microbiological results

Data from all experiments except experiment 7 were combined to increase the

statistical power of the analysis. Experiment 7 was excluded because on this occasion

the flumes blocked, and not all experimental water passed through the flumes. While

the experimental conditions varied between the other experiments they were all

comparable in that all test water passed through the sponges.

3.8.1 E. coli

The E. coli data was found to be non-normally distributed and was therefore log10

transformed. The results of the t-test (Table 3.14) indicated that there was a significant

difference between Smart Sponge®

and Smart Sponge®

PLUS in terms of

effectiveness in removing E. coli from experimental water. It should be noted that the

mean value for Smart Sponge® PLUS is greater than that for Smart Sponge® because

the difference between upstream and downstream concentration was greater for this

treatment train.

Table 3.14 T-test results for E. coli

Smart Sponge® Smart Sponge

® PLUS

Mean 3.928689 4.309879

Variance 1.274325 0.070307

Observations 28 28

Hypothesized Mean Difference 0

df 30

t Stat -1.73948

P(T<=t) one-tail 0.046101

t Critical one-tail 1.697261

3.8.2 Enterococci

The Enterococci data was found to be non-normally distributed and was therefore

log10 transformed. The results of the t-test (Table 3.15) indicated that there was a

significant difference between Smart Sponge® and Smart Sponge

® PLUS in terms of

effectiveness in removing Enterococci from experimental water. It should be noted


October 2012

28

that the mean value for Smart Sponge® PLUS is greater than that for Smart Sponge

®

because the difference between upstream and downstream concentration was greater

for this treatment train.

Table 3.15 T-test results for Enterococci


® PLUS

Mean 3.816565 4.150648

Variance 0.662933 0.027441

Observations 28 28


df 29

t Stat -2.12761

P(T<=t) one-tail 0.020998


3.8.3 Coliphage MS2+

The coliphage data was found to be non-normally distributed and was therefore log10

transformed. The results of the t-test (Table 3.16) indicated that there was not a

significant difference between Smart Sponge® and Smart Sponge

® PLUS in terms of

removing coliphage from experimental water. It should be noted that the mean value

for Smart Sponge® PLUS is greater than that for Smart Sponge® because the

difference between upstream and downstream concentration was greater for this

treatment train.

Table 3.16 T-test results for coliphage


® PLUS

Mean 7.729456239 8.254256543

Variance 2.652768931 0.035604703

Observations 25 25


df 25

t Stat -1.600365825

P(T<=t) one-tail 0.061040039


3.8.4 Attenuation of Faecal Indicator Organisms

To assess overall attenuation for each of the FIOs, the mean of the percentage

reductions was calculated for each. As an indicator of the confidence with which these

attenuation values can be considered the standard deviation was calculated, with a

confidence limit of two standard deviation units provided.


October 2012

29

Table 3.17 Attenuation of faecal indicator organisms expressed as a mean

percentage reduction with confidence limits of ±2 S.D.


® PLUS

Mean %

Reduction

± 2 S.D. Mean %

Reduction

± 2 S.D.

E. coli -12.0 98.5 -99.9 0.24

Enterococci -37.7 118.1 -99.5 1.39

Coliphage 318.1 2,869.2 -51.2 396.6

3.9 Summary of microbiological results

The t-test results indicate that there is a significant difference between the ability of


® PLUS treatment trains to remove E. coli and

Enterococci from experimental water. There was, however, no significant difference

between the two treatment trains in terms of removing the coliphage MS2+.

This is reflected in the attenuation of the FIOs, as expressed by the mean percentage

reduction and associated standard deviations (Table 3.17). The Smart Sponge®

treatment train did result in an overall reduction for both E. coli and Enterococci,

although the reduction was modest at 12% and 37.7% respectively. The confidence

limit for both these parameters is high due the substantial variation in results. In

contrast, the Smart Sponge® PLUS treatment train resulted in a mean percentage

reduction of -99.9% and -99.5% for E. coli and Enterococci respectively, with the

reproducibility of these results reflected in the substantially smaller confidence limits.

With regard to the coliphage results however, the results are different. Smart Sponge®

treatment train resulted in a net overall gain of 318.1% and had an extremely large

associated confidence limit. While the Smart Sponge® PLUS treatment train did result

in a mean percentage reduction of -51.2%, the confidence limits are again substantial,

indicating the large degree of variability in the results.


October 2012

30

4 DISCUSSION

4.1 Flow rate and suspended sediment addition

The flow rate of water through treatment trains is influenced by the gradient over

which the water flows (B. Marshall, pers. comm.). As indicated in Figure 2.2 and

Figure 2.3, the gradient of the flumes during these experiments was not substantial

and it is considered that this will have affected the results so far as flow rates

obtained. As indicated in Table 3.1, the flow rate of the clean treatment trains was

0.4 l/s for the Smart Sponge®

flume and 0.29 l/s for the Smart Sponge®

PLUS flume.

This is lower than the rates indicated for the following conditions (B. Marshall, pers.

comm.) where the treatment train is composed of two Smart Sponge®

smart packs

located ahead of seven Smart Sponge®

PLUS smart packs. During the experiments the

experimental water did flood the flumes behind the packs, so flow rate from the

header tank was not a limiting factor, rather the shallow gradient of the flumes.

Head of Water Flow 300mm - 0.69 Litres/sec/Pak

600mm - 1.58 Litres/sec/Pak

900mm - 2.48 Litres/sec/Pak

1.2m - 3.37 Litres/sec/Pak

While not directly measured, it is considered probable that the head of water for these

experimental runs was less than 300mm.

Observed flow rates were reduced rapidly once experiments with added suspended

solids were run. The first experiment run (Experiment 7) had ca. 1,000 mg/l added

suspended sediment in an effort to replicate conditions that might be experienced

during a rain event (e.g. Gupta and Saul, 1996; Rossi et al., 2005) and this resulted in

the flumes blocking, with an associated decrease in flow rate. While the flumes were

backwashed, flow rates equivalent to those obtained during the test of the flumes were

not obtained again. The possibility exists that despite backwashing, the treatment

trains remained blocked to a degree with suspended sediment and that this affected all

following results for flow time.

With regard to the blocking experiments, the fine-sediment blocking experiment

clearly resulted in a sequential decrease in flow rate as additional sediment was added

to the flumes (Table 3.6 and Figure 3.1). The faster running Smart Sponge® flume

decreased by ca. four times, while the Smart Sponge® PLUS flume decreased by

about three times. The results of the suspended sediment analysis clearly indicate that

the sponges filter suspended sediment from the water running through them. This

suggests that should the field set-up not prevent fine sediment as well as coarser

sediment from entering the treatment trains that flow rate will decrease, potentially

risking the system to back-up and overflow, with the result that the storm water is not

treated. Given that there are indications that the antimicrobial agent needs to be kept

clean to function at it’s greatest efficiency (XMicrobes website, see Section 1.2), this

may also have implications for treatment effectiveness.


October 2012

31

It is notable that the experiments where blocking was attempted via the addition of

used motor oil did not result in a reduction in flow rate in either flume (Figure 3.2),

but that the Smart Sponge® PLUS flume had a substantially lower flow than the Smart

Sponge® flume. These results indicate that the Smart Sponge

® treatment packs are

indeed effective at adsorbing hydrocarbons, and that this does not effect the flow rate,

but that the flow rate in the Smart Sponge® PLUS treatment packs is substantially

reduced should they come into direct contact with hydrocarbons. This reduction is

accounted for in the treatment options offered by SmartSponge Products Ltd, as they

recommend that at least Smart Sponge® packs are placed ahead of any Smart Sponge

®

PLUS packs utilised (B. Marshall, pers. Comm.).

4.2 Microbiological results

Overall the results clearly indicate that the Smart Sponge® PLUS treatment trains are

highly effective and consistent at removing E. coli and Enterococci from wastewater.

A significant difference can be observed between the two treatment trains, with Smart

Sponge® PLUS resulting in lower downstream microbiological concentrations. Only

on two occasions during the experiments run did the Smart Sponge® PLUS flume

produce results indicative of an increase in concentration: during the first experiment

run (Experiment 7) and during the last experiment run. It is considered possible that

during Experiment 7 when the flumes blocked, that the weight of the water forced

experimental water down the sides of the treatment train and that the initial sample

collected was contaminated. Later samples from this experiment were not

contaminated because the flume sides blocked from the added sediment and all

downstream water had only run through the treatment train. It is also notable that only

E. coli was present in the downstream sample, while Enterococci were apparently

efficiently removed. It is unclear why the last sample collected during the used engine

oil experiment was contaminated.

In contrast, the Smart Sponge® flume was more variable, occasionally indicating a

decrease in microbial concentration, but frequently indicating an increase. This raises

the possibility that the microbes were held during the sponge matrix, or in association

with the trapped suspended sediment and on occasions washed out into the

downstream water. In support of this, it can be observed that significant decreases in

E. coli were observed in only early experiments (1 and 3), when it might be

considered more likely that the treatment train would trap sediment and any

associated microbes. During later experiments, when the burden within the treatment

pack was higher, there is a greater chance that microbes would be washed out.

It is notable that during the fine-sediment blocking experiments that while the Smart

Sponge® flume was inefficient at removing E. coli or phage, a pattern of reduced

Enterococci concentrations was present (Table 3.8). This could indicate that the

Enterococci were associated with the fine sediment fraction, and were held in the

treatment train along with the sediment.

With regard to the coliphage the results from both treatment trains are highly variable,

and a significant difference between them cannot be demonstrated. This suggests that

the Smart Sponge® PLUS treatment packs do not remove the coliphage itself, and

raises the possibility that the coliphage may be retained within the sponges resulting

in elevated concentrations at a later time. The coliphage was added directly to the


October 2012

32

experimental water, on the assumption that the mixing provided by the pump would

have been sufficient to mix the coliphage thoroughly. If the mixing provided by the

pump was not sufficient then it is possible that the coliphage remained ‘clumped’

within the experimental water, and this could have contributed towards the uneven

results observed. Mixing the coliphage with an aliquot of experimental water before

adding to the upstream water butt would be recommended for any future trials to try

and remove this possibility.

The Smart Sponge

® PLUS treatment pack demonstrates an attenuation (mean %

reduction) of -99.9% and -99.5% for E. coli and Enterococci respectively, with

confidence limits of 0.24% and 1.39% (respectively). This clearly demonstrates the

effectiveness of the antimicrobial agent. In contrast, while the Smart Sponge®

treatment train did result in an overall reduction for E. coli and Enterococci the mean

% reduction was much smaller (12 and 37.7% respectively), and less consistent.


October 2012

33

5 REFERENCES

Gupta, K. and Saul, A.J. (1996) Specific relationships for the first flush load in

combined sewer flows. Water Research 30: 1244-1252

Rossi, L., Krejci, V., Rauch, W., Kreikenbaum, S., Frankhauser, R. and Guja, W.

(2005) Stochastic modelling of total suspended solids (TSS) in urban areas during rain

events. Water Research 39: 4188-4196

Shapir, S.S. and Wilk, M.B. (1965) Analysis of variance test for normality (complete

samples). Biometrika 52: 591-61

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