Bio Polymer Technique for Slurry Trenches

Guar Gum is a natural substance that acts as a natural food thickener serving identical purposes as tapioca flour, cornstarch or the locust bean gum. However, the thickening abilities of Guar Gum are considered to be much higher than that of corn starch, at a fractional cost! This makes Guar Gum a highly preferred food thickener, used extensively for the commercial production of ice creams and puddings. Until the recent ban issued by the FDA, Guar Gum was also used as a key ingredient in non prescription type diet pills that were formulated for creating a false sense of fullness, leading to restricted intake of food. It is also used as a thickening agent for several other industrial purposes as well.

The gum originates from the guar plant or the cluster plant. The plant is found in North India and parts of Pakistan. The seeds of the plant are manually separated and processed into flour, being sold as split seeds subsequently. The cluster plant is a major cash crop for the Pakistani and Indian economies.

The Bio-polymer Technique in a Nutshell

A bio polymer drain is a deep drainage trench with the bio-polymer slurry . Most often, these would be used as extraction or ground water interceptor trenches for collecting and removing groundwater. They can also be used as devices for de-watering. The trenches work like intercepting barriers by intercepting contaminated ground water plume, allowing air sparging systems to remove the pollutants present in groundwater, curbing water contamination.

The slurry trench method or technique is employed to construct the B-P drains. The process involves the usage of guar gum which is an organic polymer that is commonly used as a food thickener. Although bentonite happens to be the more ordinarily used ingredient for such purposes,guar gum has its own advantages. Unlike bentonite, the gum would not seal the walls of the trench. When guar gum powder is mixed thoroughly with water, what we get is a biodegradable fluid that is highly viscous and pseudo plastic in nature. The high gel quality and associated strength of this slurry acts just like a drilling fluid. As a result, the hydro-static pressure is transferred from to the walls of the trench from the slurry.

In normal circumstances, the slurry is supposed to last for a couple of days to a maximum. It depends on the characteristics of the source water and the ground water, on prevailing temperatures and also on the properties of the soil. However, additives are available which when introduced in the right fashion and maintained properly could contribute to enhancing the life of the slurry to around 14 days. Post the backfilling has been completed with stone or sand backfill which also acts as permeable barriers, the development process commences as the slurry present within the trench starts breaking down. The breaking mechanism is fuelled by the natural enzymes which are present in the soil that has been consuming the biopolymer. Breaker solutions might also be introduced for expediting the complete process. Once the slurry has been completely broken, the trench now becomes permeable, allowing the restoration of the actual hydraulic connectivity of the site. Subsequently, it turns into water.

The Slurry Production Norms

Be it bentonite or guar gum, the preparation of slurry requires adherence to specific norms and regulations. Normally, the guar gum is mixed in water in a high speed mixer in order to hydrate it completely. Once the hydration has been completed, it is directly sent to the trench via a temporary hose. Throughout the usage and production of the slurry, the composition needs to be monitored with the aid of strict quality control mechanisms, inside the trench and also during the mixing phase. A lot would depend on the prevailing temperatures. For instance, lower temperatures would mean lesser usage of preservatives and reduced efficiency of enzymes present within the slurry. Hence, decomposition would normally take longer. These are some of the factors to keep into perspective when preparing the slurry.

Usages of Bio Polymer Techniques

The Bio Polymer trenches are used for:

· Installing leachate systems around the landfills.

· Collecting loads of hazardous wastes migrating from industrial sites.

· Facilitating dam stabilization through toe drains.

· Creating reactive barriers that are permeable in nature.

· Stabilizing landslides.

The Advantages of the Bio Polymer Trench

There are a slew of advantages of the B-P drain technique. Some of the prominent ones include:

· The B-P technique emerges as a preferable alternative especially when compared to traditional and the more conventional techniques. Always dewatering a particular site and subsequently proceeding to use shoring and sheeting techniques may not always be possible. The B-P drains would be considered more effective since they would be more cost effective and would be requiring shorter time for processing.

· B-P drains are also considered safer since no one is actually required to physically enter the excavated trenches. All the work can be completed from the surface itself.

· The environmental impact is also substantially minimized. This is because; the B-P method essentially allows narrower construction of trenches as compared to conventional techniques. This becomes specifically relevant when dealing with sites with a significant amount of contamination because excavated spoils of compromised qualities would be created.

· The cost of backfill materials are also minimized on account of the controlled dimensions of the trenches.

· There would be no water disposal or storage problems arising from the dewatering systems.

· The trenches are constructed without any form of shoring. Therefore, installing leachate lines subsequently would become much easier.

Thus, clearly, the slurry trenching method using bio polymer provides a more viable alternative when compared to the more conventional and traditional techniques. The duration of the project would be shorter and the costs lesser. Safe environment for work can also be provided with ease. Besides, the technique serves various advantageous purposes. Therefore, most likely, there would be many implementations of the B-P drain method in the near future in both environmental and civil applications.

 

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