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Theme: Sustainable waste and water management. SUMMARY ... trial and error method; robustness of the set up was tested to reproduce consistent results.
Performance Testing of ‘Comb Separator’- A Novel Sewerage Overflow Screening Device M.A. Aziz1, M.Imteaz1, H. M. Rasel1, D. Phillips2 1

Swinburne University, Faculty of Science, Engineering and Technology, Melbourne, Vic, 3122, Australia Water Solutions (Aust) Pty Ltd., Heathmont, Melbourne, VIC 3135, Australia. Corresponding author: Abdul Aziz. [email protected] 2

Theme: Sustainable waste and water management

SUMMARY Rivers and creeks receive a lot of sewer solids due to sewer overflow. This overflow causes a serious concern for the environment, aesthetics and public health. To overcome such sewer solid overflow, different types of screening device were developed. The initial expense, maintenance costs, poor sewer capture efficiency and blinding on the screener are discussed as these are the limitations of the overflow devices. Most of the screener has electro-mechanical systems which are expensive, complex and cause concern for possible malfunctions in unstaffed remote locations. Consequently, a novel sewerage overflow device ‘Comb separator’ was developed and tested. Optimum criteria were achieved for the device using trial and error method; robustness of the set up was tested to reproduce consistent results. There was minimal blockage on the screener and higher capture efficiency than Hydro-JETTM. The ‘comb separator’ has a good application potential to improve the sewer solids capture in the urban sewerage system.

KEYWORDS Capture efficiency, Sewer solids, Screening device, Optimum experimental setup

1. INTRODUCTION Under wet weather conditions, sewer overflows cause serious concern to the environment, aesthetics and public health concern. In order to reduce these sewer solids, different types of screening devices are used in existing network. In most cases screening is the only economically viable method according to Faram et al. (2001). These issues trigger the need to research different types of screening devices and screening handling systems. Reported literature suggests that screens need to be ‘self-cleansing mechanism otherwise placed in combined sewer environments these are subject to blinding (Aziz et al., 2013). Usually most ‘conventional’ screening systems utilize electro-mechanical components to facilitate such a process. However, given the harsh unmanned remote environment of the sewer overflow device locations; this is clearly not ideal. To overcome such problems a novel self-cleansing, less expansive, low maintenance with no moving parts sewer overflow screening device is proposed. Simon and Phillips (2008) developed a sewer overflow screening device with temporary holding tanks that provides transient storage and real time control of sewer systems. The device further updated by Aziz et al., (2013), the device has no moving parts and has a robust stop/start operation, but blinding on the screener which lead to low capture efficiency was a limitation in the device. This research focuses on performance testing of the proposed ‘Comb Separator’ device to ensure the best performance for capture efficiency. A series of laboratory tests was carried out to evaluate steady state; short duration (varied from 6 to 32 minutes) flow conditions having flow variation from 20 to 70 l/s. Instead of using static screens that have a high maintenance cost, a self-cleansing comb separation device is proposed. In analyzing results will discuss about the key experimental conditions like flow, comb spacing, comb layers, weir opening, robustness etc. Some of the key findings from the experiments include the followings:  To analyse capture efficiency for sewer solids more than 10mm diameter  To understand impact of experimental design parameters of flow discharge, weir opening, comb spacing and layers against sewer solids capture efficiency.  Robustness of the device set ups to make sure re-produce of consistent results on the optimum experimental set up.  Compare performance of the proposed ‘Comb Separator’ with standard ‘Hydro-JETTM’ device on low flows (up to 60 l/s).

2. METHODS To test the performance of the experimental set up flow discharge, weir opening, spacing and layers of combs were adjusted. The aim was to achieve high capture efficiency over 80%, with minimal blockage on the combs and test on 1 in 1 year overflow by formulating experimental set ups as trial and errors. The experimental

methodology adopted design experimental set up should 70 l/s, blinding on the screener less than 5% on the screening combs and sewer solids capture efficiency more than 80%. Robustness of the optimum experimental setup was checked by repeating experimental results with reasonable consistency of the experimental results.

3. RESULTS AND DISCUSSION  Sewer solids more than 10 mm diameter captured more than 95% with the new screening device The proposed ‘Comb Separator Device’ performed highly efficient where capture efficiency achieved more than 95% for sewer materials more than 10mm diameter. The sewer solids used in the testing including toilet paper, bottle tops, bottle can, dish wipes, tampons, condoms, cotton balls. Blinding on the combs was negligible during the tests.  Minimal blinding on combs were observed, increasing effective Comb spacing improves capture efficiency The effective comb spacing reduces less than 2mm minor blinding occurs on the combs; however effective screening more than 3.5mm minimal blinding were observed during the experimental testing.  Comparison of Performance between Hydro-JetTM and Comb Separator HYDRO-JETTM Static Average total Efficiency (%) Number of Observations Flow Range (l/s) Average Flow (l/s)

Screen Mesh Aperture Size (mm) 6 4 2 51

67

69

17 17 - 60 45

20 18 - 60 43

12 17 - 45 33

COMB SEPERATOR Effective Comb Spacing (mm) Effective Gap between 4.8 4.5 1.5 combs Average total Efficiency 90.7 83.7 66.5 (%) Number of Observations 6 14 6 Flow Range (l/s/m) 20 - 67 15 -30 30-70 Average Flow (l/s/m) 48 22 47

4. CONCLUSIONS A series of trials with different numbers of combs, spacing of combs, flow volume and weir opening were tested. Some of the key findings from the experiments are summarise below: 

The proposed device can capture larger sewer solids more than 10mm diameter over 95% capture efficiency.  Comparison suggested that Comb Separator shows minimal blockage and higher capture efficiency on low flows over Hydro-JetTM. The hydraulic experiments suggested good application potential of the proposed device in the urban sewerage system. Further experiments are suggested with higher flow (up to 120 l/s) especially with sewer solids dimensions less than 10 mm.

REFERENCES 1.

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Aziz, M. A., Imteaz, M., Choudhury, T. A. & Phillips, D. (2013). “Applicability of artificial neural network in hydraulic experiments using a new sewer overflow screening device”, Australian Journal of Water Resources, Vol. 17, No. 1. Faram, M.G., Andoh, R.Y.G. and Smith, B.P. (2001). ‘Optimised CSO screening: A UK perspective’. 4th Novatech International Conference on Innovative Technologies in Urban Drainage, Lyon, France, 25-27 June, 2001. Simon. M. and Phillips, D.I. (2008). ‘The development of a sewer solids screening system for CSO chambers’, 11th International Conference on Urban Drainage, Edinburgh, Scotland, UK 2008.