Options for Advanced On-Site TreatmentK. M. Bellamy1 and Brian Horsley2
Vital Resource Management Pty Ltd, P.O. Box 350 Deeragun Qld 4818 Australia
Vital Resource Management Pty Ltd, 122 Parkdale Dve Leslievale Tas Australia
Identification of specific elements of a process stream and the ability to purchase elements either as a package or individually offers end-users flexibility and encourages understanding of the processes by those who have to use them. Incorporation of EM® (Effective Micro-organisms®) based, low-energy, low-technology elements has allowed clients in sensitive areas to tailor a “modular process stream” which best suits their site and which allows meeting of the highest standards for effluent treatment and re-use. Incorporation of microbial balancing by regular inoculation enables the systems to cope with the serious problems of fluctuating loads and odour generation. A simplified process stream approach allows minimal maintenance on remote sites and multiple failsafe mechanisms including advanced oxidation to allow the process to produce high levels of effluent quality in extreme circumstances.
There are currently twenty-six Government approved on-site treatment packages available in Australia to developers. Distinguishing the benefits and disadvantages of these prepackaged options is often clouded by proprietary focus or a lack of prior experience on the part of the environmental license holder or land developer. Mechanically intensive operations and concurrent maintenance issues make most of these unsuitable for sensitive and remote sites.
Australian Environmental Protection Act provisions regarding waste water have been significantly tightened in the past ten years. An example of this is found in sites within the Great Barrier Reef Marine Park area where all EPA License renewals since 1998 include a provision for nil discharge to waters. In addition, incorporation of AS,NZS 1547-2000 (On Site Sewerage Treatment) and an upgrade of Water and Sewerage Acts has seen a renewed focus on water quality outcomes and suitability of a given process for a given site. Inclusion in Australian Standards of design criteria for a range of discharge methods has also fostered a willingness to explore advanced treatment outcomes which do not focus entirely on mechanical processes.
Two prominent factors influence treatment of waste water in sensitive sites in Australia: the tyranny of distance and seasonal fluctuations in population. Distance has traditionally played a major role in system failure as maintenance presents a difficult and expensive proposition and is often overlooked as a result. Seasonal variations in occupancy have an extremely deleterious effect on operation of aerated waste water treatment plants.
It is not unusual for a system to experience nil to 10% load for several weeks followed by maximum capacity for several days. Maintenance of biomass using traditional activated sludge or batch reactor processes can be nigh impossible under these conditions.
These factors make a biologically balanced approach such as that offered by an integrated augmentation program using EM® and a low maintenance system design increasingly attractive options.
Materials and Methods
The Modular Process Stream offered consists four basic “Elements” which are each contained in discrete chambers (tanks) and sized and sited appropriate to the requirements of the particular operation. A brief description of these elements is included below. Typically, each system incorporates an augmentation phase where EM® is added to collected effluent, a sedimentation phase where fermentation and rapid settlement of solids is promoted, an aeration phase where both intermittent and constant aeration are used to promote growth of cultures and an advanced oxidation phase where rapid disinfection and final BOD removal is completed.
Figure 1. Modular Process Stream - Collection and Inoculation Phase
Figure 2. Modular Process Stream - Sedimentation and Aeration Phases
Figure 3. Modular Process Stream - Advanced Oxidation Phase
Results and Discussion
The “Modular Process Stream” approach allows the perpetuation of some established techniques such as the use of septic tanks and the promotion of biological reactions rather than mechanical processes. These are supported where necessary by “higher-tech” options which help satisfy health and related concerns and offer failsafe measures for events such as system overload as illustrated in Figures 1-3, Modular Process Stream.
A discussion of the four basic elements of the process stream follows:
a. Biological Augmentation
Systems make use of a proprietary technique for microbial balancing (AP 737685)
employing a multi-point, low dose, constant inoculation pattern which allows a partially self-perpetuating culture of organisms to develop and which overcomes environmental shock loads normally experienced by introduced organisms. With use of EM®, cultures are adaptive and persistent. Where inoculation is maintained, odour control is constant throughout a treatment system, and systems demonstrate stability of biological activity despite fluctuating loads. EM® demonstrates an ability to begin organic treatment of effluent in collection networks prior to a conventional treatment plant.
Table 1 shows reductions of biological load gained in a dosed collection system only (prior to Treatment Plant) over a seven month trial in one system.
Table 1. 80th Percentile Spread of Selected Effluent Quality Data in Collection System Prior to STP
|Indicator||Units||Baseline Period (10 Weeks) Before EM® Begun||Acclimatising Period (14 Weeks) EM® Program Established||Stabilised Period (10 Weeks) EM® Program||% Change in Load|
|BOD||Kg/day||549.81||527.81|| 493.8 ||-10.19|
|SCOD||Kg/day|| 296.05||293.23||258.08 ||-12.82|
Use of EM® has particular benefits in advanced sedimentation and consumption of solids. A significant concern in remote sites is the periodic removal of accumulated solids from septic tanks or similar chambers. Table 2 - Sludge readings, show collated data from primary collection chambers at a number of sites over a two year period. To date none of the sites employing EM® in an enhanced sedimentation phase has required a pump-out.
Table 2. Sludge Depth in Primary Sedimentation Chambers with EM® Inoculation.
|Site ID||Effluent Flow (L/day) (Liters)||Primary Chamber Volume||Sludge Depth Oct '99||Sludge Depth April '00||Sludge Depth Oct '00||Sludge Depth April '01||Sludge Depth Oct '01|
Inclusion of aeration and settlement chambers including the use of low-energy flow balancing and frictionless aeration compressors make these standard elements very user friendly.
d. Oxidation and Advanced Oxidation
For sites where footprint size of the treatment plant limits biological reaction time, a true rapid oxidation process using ozone (generated on site) offers considerable benefit in reduction of BOD and TSS to consistently outperform Advanced Wastewater treatment guidelines for these indicators. A proprietary technique APP uses Residual Ozone and UV in synergy to provide a double barrier for pathogen control and a significant ongoing benefit in terms of residual oxidation potential without the use of chlorine. In addition, the advanced oxidation process allows for almost complete removal of BOD and TSS. Final waters can be left with consistently high and persistent levels of DO and show little or no pathogen re-growth. This allows reuse with confidence in high-impact areas such as resorts and commercial establishments. (Table 3)
Table 3. Collated Effluent Quality Date, Palm Bay Long Island Resort
A significant result observed in these systems is the formation of high levels of dissolved oxygen in final waters. Boon and Lister (1975) have shown that presence of dissolved oxygen mitigates against formation of odorous compounds (particularly hydrogen sulphide) in effluent waters. In addition, high levels of dissolved oxygen (DO) which persist in final effluent waters indicate a residual oxidation potential gained without the introduction of chlorine. This represents a significant cost saving for operators and an environmental benefit in reduced formation of chloride compounds.
A modular process stream approach to waste water treatment offers a stable and flexible treatment process especially suited to sensitive and remote sites. Use of low-tech processes backed by consistent augmentation with effective microorganisms and advanced oxidation allows extremely high treatment outcomes in a low maintenance environment.
The production of high and persistent DO in final waters allows little or no pathogen re-growth and permits the storage and re-use of effluent in a range of circumstances without odour generation.
AP. Australian Patent 737685, Method of Treating Waste Water, Bellamy, K.M., Newton R.K.
APP. Australian Provisional Patent PR5732, Method and Apparatus for Water Treatment.
Boon, A.G. and A.R. Lister. 1975. Formation of sulphide in rising main sewers and its prevention by injection of oxygen, Progress in Water Technology, 7 : (2)
EM Inoculation Process - Island Resort
Modular Process Stream - Treatment Plant site