How to solve wastewater problems on shoppings malls

October 31, 2019
Posted in DAF

The problem

Wastewater treatment solutions for shopping malls represent an important challenge for the sustainability of these infrastructures. It is common sense that shopping centers and malls are energy and water “black holes”, given their dimension, impact, people served, services, and conveniences. Therefore, consultants, engineers, investors, promoters, and entrepreneurs have been putting great effort into developing new projects and facilities to reduce the malls’ carbon print.

The food court of the shopping centers is a rather critical source of environmental issues and complications. Ensuring that the building is supplied with quality water is quite challenging. Usually, those are the main concern of promoters. Basically, all this water will be returned to the city as wastewater, contaminated with organic and inorganic matter. Cooking, dishwashers and washing facilities, floors, and equipment generate highly contaminated wastewaters. Those wastewaters will be drained into the sewage system, on an average of 7 liters/meal, loaded with grease, fats, food wastes, sugar, proteins, salt.

The used approach on wastewater treatment solutions on shoppings

To face a wastewater treatment solution on shopping malls, the widely used approach is to install grease traps with downstream dedicated duct lines for draining waters from restaurants, cafeterias, coffee islands, fast-food areas, and food corners. The waters coming from these sources are rejected into the public sewage network, then feeding public wastewater treatment plants.

From a conducted survey, we concluded that the majority of malls and shopping centers have serious compliance problems with the waters coming from grease traps. In fact, grease traps are basically tanks where wastewaters, loaded with greases, fats, detergents, and other organic matter. They rest for some time (depending on their dimensions’ calculations) to allow these low-density elements to come to the surface and get trapped in the tank.  Meanwhile, lower layer waters are drained out of the tank, in a plug flow process. Taking that in mind, it becomes clear that several problems arise from these grease trap systems.

Here are some of those issues:

  • Dimensioning and calculations are systematically wrong to meet the needs of the shopping mall activity. Builders or main suppliers tend to select and install the cheapest, poorer, and smaller units possible. Furthermore, underwater calculations are usually too optimistic compared to real-life usage. Unfortunately, often promoters have little to no idea of this situation. They don’t realize the real problem until they are approached by the authorities. As the cost of these systems is ridiculously low, it does not call the attention of promoters.
  • Restaurants, food corners, and other areas usually rely on rather poor procedures, control, and rules concerning water usage and wastes management. Thus, everything goes down the drain. These situations are rarely caught by the local management or authorities;
  • The common drainage system for all the parts of a food court ends up eliminating accountability and liability for problems that may arise. “In-house” situations (blockages, leaks) or outside ones (noncompliance with local regulation, municipality fees, or fines);
  • Grease traps are designed to retain wastewaters for an established period. Loaded with easily degradable organic matter, the fermentation phenomena is very rapid, generating bad odors, fat acids, bio-gas, and increasing organic loads that will affect the downstream treatment plant. Often, grease traps are not complying with the majority of reject limits for wastewaters established by local authorities;

Grease traps should be emptied and cleaned very often, depending on size and usage. Thus, when installing grease traps, requiring easy access for vacuum trucks is a very important detail. Unfortunately, this is rarely considered in projects, as it generates a huge cost. For example, vacuum trucks and managing liquid grease and fats from these traps can cost as much as 50€/ton. Consequently, vacuum trucks end up not being considered as a priority investment for the shopping malls’ administrators. It ends up retaining greases inside the trap longer than the recommended.

The future of wastewater treatment solutions on shoppings

The paradigm is changing and new management and construction philosophies are emerging with ideas of sustainability. Sustainable shopping centers and malls are the flagships for promoters and investors. Sustainable shopping centers mitigate the high energy costs, that currently impact so greatly the management cost. Besides, the water cost has also become an issue, especially in countries where it is usually high or in countries suffering from water shortages. Fortunately, sustainable malls also enable better water care and optimization. The possibility of reusing wastewater is becoming an important topic. Closing the water cycle in shopping facilities is the next trend in the field.

VentilAQUA is eager to help engineers and companies specialized in water management and water systems with more sustainable solutions. VentilAQUA counts on a solid experience in these solutions. Water reuse is a daily reality and our technologies and equipment ) are adapted to the specific needs of a shopping center. The wastewater treatment solutions on shoppings and its reuse, like in washrooms (as flush waters) or garden irrigation.

We are able to replace standard or even more sophisticated grease traps by chemical treatment units. With flotation devices (DAF), VentilAQUA manages to perform a proper chemical treatment into the wastewaters, removing all solids, fats, and greases. Moreover, it enables a drastically decrease of organic loads, preparing the waters for final disinfection and filtration. As a result, it will then allow them to be reintroduced into an internal feed line to flush waters and irrigation.

VentilAQUA is a specialist in developing these DAF chemical units. These units present a very low footprint, thus allowing their installation in small rooms available in technical areas or underground parking lots. They even enable the reuse of the existing grease traps as buffer tanks and initial solids removal (through a physical operation – grid or sieve). These tanks, reused or new, are aerated, thus eliminating any risk of bad odors. They also facilitate chemical treatment by enabling very effective aerobic chemical reactions. From these buffer tanks, waters are fed into the DAF unit, where an automatic chemical treatment and pH measuring and control cleans them, removing all fats, greases, and solids. Clear and treated waters are then fed into multimedia filters and endure a disinfection operation. Afterward, they are available and proper for reuse.

Advanced Oxidation Technology

VentilAQUA also brought wastewater treatment solutions to shopping malls with advanced oxidation technology (using electricity). It is called electrocoagulation and electro-oxidation, which allows a more intense and efficient organic matter removal without chemicals, managing to reduce contamination to very low levels, and allowing to use common multimedia filters with longer lifetime and to reuse these waters. Without this electrocoagulation, one could remove greases and fats from wastewater, but could not reach a treatment level that allows water reuse.
Now, since one of the most important indicators managers consider is operating costs and payback time, it is important to refer some number to the electrocoagulation technology. In fact, VentilAQUA has experienced under 1 year payback time and water consumption reduction. In a real client case, about 90% of the food court wastewater was recovered into flushing toilets, consequently reducing dramatically water consumption in toilet rooms.

Other important advantages associated with the electrocoagulation solution were the elimination of complex removal residuals and the simplified trucking of liquid wastes, which are always fully loaded. This positive impact allowed for a huge cost elimination (50,00€/ton on trucking vs. 1,50€/ton on treatment), as well as the elimination of bad odors sources, which usually cause disturbances to employees, users, and neighbors life.

Managers and promoters can easily establish new criteria and new parameters for water costs in their projects. Just with a single facility, they can comply with all local regulations for wastewater reject. It eliminates any risks of noncompliance and undesired fines and public negative impact. Also, reduces water consumption, reduces overall capital, operating costs, and make their facilities more sustainable and greener. All of this will obviously attract the sympathy of customers, users, and surrounding communities.

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