PACKAGING
MACHINERY
CHEMICALS & ELASTOMERS
INDUSTRIAL MATERIALS
MERIDIAN AQUATIC TECHNOLOGY AUSTRALASIA LIMITED
PART OF THE TCL GROUP
THE AQUAMATS® PROCESS
ADVANCED MICROBIAL TREATMENT TECHNOLOGY FOR WASTEWATER TREATMENT PONDS
In the past, aerated lagoons were the ideal process for treating municipal and industrial wastewater.
Low capital investment, low operating costs and very limited maintenance requirements made this the affordable treatment of choice for many New Zealand communities.
Today, increasing loads combined with more stringent environmental constraints render many of these pond systems out of compliance. In most cases there has been no alternative other than the adoption of capital and technology intensive upgrade options with their associated high maintenance and operating costs.
No alternatives? AquaMats® Process technology has recently been introduced into New Zealand to give local authorities and industries the possibility to increase their existing pond capacity by up to ten times, without extensive capital investment and at the same time, retaining low operating and maintenance costs.
Originating in the United States, AquaMats® Process technology has been developed by the biological and wastewater engineers from Meridian Aquatic Technology. Over the last ten years the technology has been refined to the stage where it is now widely implemented over a broad range of differing aquatic applications throughout the world.
AquaMats® wastewater technology has evolved from use in intensive aquaculture production (fish, shrimp farming), where high standards of water quality are absolutely critical. AquaMats ® ach ie ved these standards whilst routinely dealing with loadings equivalent to, or greater than, typical loadings found in municipal wastewater treatment plants. In many of these production facilities, final effluent quality achieved meant conditions of zero water discharge were met.
Having achieved excellent results within these high loading environments, Meridian directed their attention towards the area of industrial and municipal wastewater treatment. It is this application area that is of most interest to Colin Weeks, who is overseeing the introduction of AquaMats® technology for Meridian Aquatic Technology Australasia. “This technology enables pond based systems to compete performance-wise with high-rate options at lower capital cost and much lower operating costs. The challenge is to convince consultants, councils and engineers that something this effective is available, with all the necessary guarantees in place.
Description of AquaMats®
AquaMats® are a high surface area media designed to maximize colonization by beneficial bacteria and algal communities that inhabit the wastewater environment. In contrast to floating or fixed plastic growth media, AquaMats® are designed to promote an optimal environment for bacteria and higher organisms, creating a habitat similar to that found in natural ponds and rivers. This unique material construction makes AquaMats® an extremely efficient surface media, resulting in the effective reduction of BOD5, TSS and Ammonia.
Biphasic Surface Area
AquaMats® offer a biphasic surface structure, a key component to the success of this product. During the production process, the material is woven at different densities on opposing sides of the fabric, designed to create a difference in the oxygen transfer rates. This rate differential results in a thin anaerobic or anoxic zone on one side of the fabric and an aerobic environment on the other. This contributes directly to both nitrification and denitrification occurring in close proximity on just the one surface area media, greatly enhancing the AquaMats® ability to accelerate the reduction of ammonia.
Fiber Design
The polymer material is designed to specifically incorporate a three-dimensional fiber structure, which provides a very high surface area of fibers. Further volume is added by a secondary pore structure within each individual fiber targeted for growth of specific organisms. These pores are limited to the surface structure of the fiber. Its physical strength is achieved through a solid core.
The upper portion of the fabric, situated closest to the light source at the pond surface, has a larger fiber pore space and is targeted for colonization by sessile cell growth. The surface area of the lower fronds of the AquaMats® is tailored for microbial growth of organisms, particularly bacterial growth in the 1~10 micron range. Overall, this specific material construction of the AquaMats® results in an effective surface area of approximately 240 m2 per meter of fabric.
Material Specifications
AquaMats® are constructed from fibers made of low density, condensed copolymers of polyethylene. This material is extremely inert and has been successfully tested for long-term durability (to EPA UV irradiation accelerated degradation standards). No plasticizers have been used in the manufacture of the fibers matrix. Life cycle testing using a series of alcohol and aldehyde extractants shows no leachate.
Pathways for Load Reduction
It is through the extensive colonization on and within the AquaMats® that a number of pathways become available for the reduction of the organic load entering the treatment plant. The microbial community consists of a diverse range of bacteria, viruses, molds, yeasts, fungi, protozoa, as well as a number of higher unicellular and multi-cellular organisms. These are all involved in many different complex reactions and interactions, ultimately converting nutrients into their final gaseous state (such as carbon dioxide and nitrogen). A parallel pathway is through the conversion of nutrients into mineralized tissue. This process results in nutrients reduction to a less soluble form. An end result is the settlement out of the nutrients in this form to the pond bottom. Protein formation and assimilation of nutrients into cellular tissue, is another major pathway for extracting nutrients from the pond system. Therefore, development up through the trophic levels is actively encouraged on AquaMats®, as this results in a very efficient incorporation of nutrients into biomass. The Columbia WWTP offers a prime example on how, through the introduction of sunfish used for grazing the AquaMats® (harvested and sold to a cat food company!), nutrient reduction and sludge minimization can be successfully combined.
Algal Competitive Interaction
Algal blooms in wastewater ponds or lakes can successfully be eliminated by the introduction of AquaMats®. AquaMats® create an ideal environment for the growth of sessile (attached) algae colonies. These directly compete with the pelagic (free-swimming) algae for the same nutrients. Pelagic algae expend a considerable proportion of their energy on adapting their position within the water column depending on the time of the day. Sessile algae don’t have this same requirement, and can therefore more efficiently use the nutrients for growth This energy expenditure differential results in the sessile algae out competing the pelagic algae for the available nutrient resources, effectively blocking the free-swimming algae (such as blue-green algae) from entering the critical (and problematic) logarithmic growth phase.
Pressure Differential Aeration
Integral to the AquaMats® system is the complementary aeration system; consisting of bottom laid, pressure differential piping (PDP). Aeration from PDP piping is extremely efficient, simulating the mixing and aeration that occurs in natural waterways. As well as efficient oxygen transfer, the aeration also provides a gyre type mixing pattern which carries the nutrients across the surface of the AquaMats®. Such benthic-deployed aeration has been used extensively in wastewater treatment for over 40 years, with many reference sites throughout North America. Twenty years ago the original 0.013” open hole piping was replaced by the self-closing slot aeration systems. The selfclosing system relies on internal pressure to open the air release slits cut along the length of the tubing, resulting in an even dispersion of fine bubbles into the water column. Unlike the previous designs, the PDP piping can be deployed over ponds with uneven bottom surfaces, as the operating pressure differential compensates for surface irregularities.
PDP Pipe Construction
The aeration tubing is a 19mm blended polyethylene pipe with integrated ballast. The slits are laser cut at varying intervals along the length of the tube. The number of slits per unit length controls the level of aeration, and the spacing between the lines allows for control of the mixing gyre that circulates the water within the pond. The aeration efficiency results in the ability to turn over the water within the total treatment pond once every 20 minutes utilizing only a minimum energy input.
System Installation
AquaMats® are installed in continuous lines by a wire cable attached to the upper sleeve. Heavy equipment or support structures are not required in most applications. AquaMats® surfaces are designed to be self-cleaning and require very modest annual maintenance. AquaMats and PDP aeration pipes can be installed, relocated or added to new or existing pond systems, often without the need for prior desludging. Installation is achieved in an extremely short timeframe and often requires no modification to the existing treatment pond infrastructure.
Plug Flow –Hydraulic Barriers
AquaMats® also function as hydraulic barriers that substantially increase the settlement of suspended solids for bacterial fixation on both the media surface and in the benthic sludge. AquaMats® provide more idealized plug flow through the pond, ensuring maximal biological contact time and maximizing the true hydraulic residence time of the pond. Specialized AquaMats® Flow-controller products are available to create hydraulic barriers or channel the flow to further optimize treatment efficiency.
Ph +64 (0)9 526 2700 Fax +64 (0)9 525 0875 sales@tclhunt.co.nz