Xogen.ca - Technology

Click on headings or scroll page

Overview
Typical Effluent Criteria
E. Coli Reduction
Conventional Wastewater Treatment
Conceptual Design of Xogen Plant
Potential Benefits of Xogen Technology

Overview

Xogen's patented technology uniquely splits the water molecule into a 2 to 1 mixture of hydrogen and oxygen gas with less electrical current than is predicted by standard laws of .

Although originally designed with energy production as the focus, subsequent testing of the Xogen technology on wastewater samples from a conventional sewage treatment plant identified potential application as a wastewater treatment process. Under specific operating conditions in a bench scale reactor, the technology has achieved high levels of and destruction at very low retention times and temperatures.

The current stage of the technology development utilizes standard off-the-shelf components and materials, has a small footprint, and is powered by 24 V DC.

It must be acknowledged that there are engineering hurdles which must be overcome to move the Xogen technology from where it is today (bench scale) to a full scale commercial process. Xogen’s technical staff is working with faculty and graduate students at the University of Toronto, Department of Electrical Engineering and Department of Materials Engineering, to address these. If the assumptions, which are supported in general by the preliminary data currently available, with regards to what the process can achieve are ultimately realized, the process has the potential to revolutionize the wastewater treatment industry.

Typical Effluent Criteria

Table 1 presents a list of regulatory parameters and levels that are currently being enforced in the Province of Ontario.

Although effluent criteria are generally specific to local conditions, the levels listed are typical of what would be expected in most jurisdictions within developed countries. All of the regulatory levels shown in Table 1 were achieved or exceeded in at least some of the Xogen tests. This indicates that the process has the potential to meet even the most stringent criteria.

The regulated levels for certain parameters such as suspended solids, total phosphorous and pathogen destruction were consistently met or exceeded in all tests. It should be noted that the residence time of 2 hours as used in the tests is very low compared to conventional treatment technology.

In a conventional air activated sludge plant, typical residence times in the aeration basin alone would be 4 to 6 hours to accomplish BOD removal. If ammonia removal were also required, these residence times would increase substantially.

E. Coli Reduction

One of the most impressive results observed was the capacity of the process to kill s.

Figure 1 shows the performance achieved in six tests conducted with different approaches to foam control and varying levels of power input. Without exception, all E.Coli were destroyed after 80 minutes of treatment and in most cases after only 40 minutes of treatment.

Although not shown in Figure 1, the results for kill from all tests conducted to date, have been consistent with this observation. The intriguing aspect of this observation is that, with the Xogen system, destruction is occurring in the presence of significant levels of .

Conventional methods of such as ultra violet light and are only effective when applied to the final which has very low levels of .

Conventional Wastewater Treatment

In order to fully appreciate the potential impact of the Xogen technology, it is first necessary to understand some of the basic premises behind conventional wastewater treatment technology.

A schematic drawing of a typical plant is shown in Figure 2. There are two additional processes which are common to conventional plants which are not shown in the figure. Prior to the raw sewage entering the it is normally passed through coarse screens and a chamber. The to the river at the end of the plant is normally disinfected and in some cases a tertiary sand filter is included where very high quality is required.

Although there are a huge variety of process trains and proprietary technologies available, conventional treatment in the municipal wastewater industry is primarily based on biological systems. The contaminants in sewage consist of suspended solid particles and dissolved organics. The larger particles are settled out in a to produce a sludge which contains easily degradable materials and requires additional treatment.

The liquid then typically enters an aerobic treatment phase where it is d with an active biomass (millions of microbial cells). Air is provided to allow these microbes to grow, multiply and keep them mixed and suspended in the liquid.

During this process, the microbes absorb the dissolved organics from the liquid and use them as the energy for during which they give off CO2 and water as the end products. They also use a portion of these organics to build new cells and increase the total population of the microbes. At the same time, the smaller suspended solid particles into the liquid phase thus making additional food available to the microbes.

When the organics have been essentially removed from the liquid stream, the microbes which have a density greater than water are allowed to settle to the bottom of a clarifier and the clean water at the top discharged to the environment. The concentrated microbes (sludge) at the bottom are then removed and either undergo additional treatment or are recycled to the aerobic stage.

One of the major problems with biological treatment processes is that they produce large amounts of sludge, consisting of the solids from the and the excess microbes, which must then undergo additional treatment at significant cost. Sludge treatment typically accounts for up to 50% of the total capital and operating costs of a treatment plant.

Figure 2. Conventional Biological Treatment

Although biological processes can be extremely complicated, they are all designed to accomplish one primary objective: convert soluble contaminants into a solid form, which in this case are the microbes, such that they can be removed from the overall liquid stream by .

Although this would appear to be a somewhat roundabout way of converting soluble organics into solid material, there are currently very few options for direct removal of soluble material from a liquid stream without going to exotic and expensive technologies such as reverse osmosis.

A process that could directly degrade soluble organics in the liquid form would eliminate the need to generate a microbial population along with the associated costs of treating the resulting residue in an environmentally sound manner. The Xogen technology has the potential to accomplish this.

Conceptual Design of Xogen Plant

Figure 3 shows a conceptual design for what a greenfield Xogen plant might look like.

Figure 3. Conceptual Design of Xogen Plant

Based on this concept, the differences between an Xogen plant and a conventional biological treatment plant (Figure2) would be enormous. In this concept, the raw sewage would first be coarse screened and degritted as in any conventional plant. In the Xogen plant a fine screen would replace the . The screenings could go directly to landfill without any further treatment therefore eliminating the production of primary sludge and the associated capital and operating costs of downstream treatment. The liquid from the fine screens would flow to the proprietary and patented Xogen treatment module. This would effectively replace the entire biological system eliminating the basin and energy required for , the production of biological sludge and the downstream processing costs such as digestion, dewatering and land application. It would also eliminate the need for of the final since this is accomplished as an integral part of the Xogen process.

The from the Xogen process would undergo solid-liquid separation either by or and the liquid would be discharged to the environment. Two boxes have been shown in Figure 3 with dashed outlines. These are processes that might be required in specific circumstances. If the criteria are extremely stringent for either or total phosphorous, a tertiary sand filter might be required. Again this is common practice in conventional plants, is not unique to the Xogen technology and the capital is not particularly high in comparison to other infrastructure components.

With respect to the box titled “Additional Solids Treatment”, it is expected that there will be a trade-off between processing time in the Xogen reactor and the stability of the solids and if this is the case, the decision would be made on the basis of a cost benefit analysis. In the worst case scenario, if the solids required further treatment, it is estimated that the associated cost would be only a fraction of that required for treating the solids from a conventional biological plant because the total mass would be extremely low by comparison.

Potential Benefits of Xogen Technology

The potential benefits of an Xogen plant using this concept as compared to a conventional biological plant are as follows:

Complete elimination of most of the infrastructure components of a conventional plant including the primary clarifier, aeration basin and air blowers, disinfection processes, sludge stabilization processes such as anaerobic digestion and final disposal or utilization of the stabilized sludge.
Huge reduction in the footprint of the plant
Complete elimination or significant reduction in sludge (biosolids) processing costs
More stable process allowing for rapid start-up and insensitive to toxic shocks. Biological plants typically have a long start-up time because the microbes must be acclimatized to the feed (sewage) and increase in concentration to the point where acceptable treatment is achieved. In addition, since a biological system relies on microbes, any components in the incoming sewage can result in either killing the entire biomass or shocking it to the point where it takes a significant period of time, sometimes days, to recover its efficiency.
The production of a significant energy source in the form of hydrogen which can be used to generate electrical energy for internal use or export. Xogen has powered various combustion devices with the hydrogen-oxygen gas liberated by the technology; such as a 1-kw Honda generator, under 90% load conditions.
All of these factors suggest that the Xogen technology would likely be extremely cost competitive with existing conventional approaches for municipal wastewater treatment.
It is also expected that the Xogen technology could be directly applied to the treatment of many industrial wastewaters and perhaps to the treatment of potable water.

The target technology is a process unit employing the Xogen technology to treat wastewater to government regulated quality levels at a life-cycle cost that is lower than conventional technologies, and to operate in a wastewater environment in a sustained and reliable manner.