Question

A large college campus dining program realized that they dispose 22,000 Lbs. food waste yearly. This is because dining facilities can’t always accurately predict the amount of food students will consume, leading to large amounts of waste daily. In addition, due to health regulations, even if a piece of food has been barely touched, the dining hall can’t legally donate it to a food bank. The university is looking into different options.

As an environmental engineer tasked with this site, Select the best bio-remediation option to deal with this problem and explain your reasoning, with advantages and disadvantages

Answer 1

Sol: Food waste is a source of an untapped energy which is mostly dumped in
landfills whereby it releases greenhouse gases into an atmosphere . It is
very difficult to treat and recycle food waste due to its composition. Food waste consists of high levels of sodium and moisture and is usually mixed with other.

types of waste during its collection. Amount of waste generated is largely determined by two factors- population in a given area and its consumption patterns. In order to cope with this huge waste production, advanced
and effective waste management systems are to be adopted that can overcome the gap between production and management of waste disposal. Bioremediation is a naturally occurring process in which microorganisms either immobilize or transform environmental contaminants to innocuous end products . Biotreatment is well accepted by industry as it goes along with the current popularity of maintaining nature’s harmony. Bioremediation has become a widely accepted option for the clean up of contaminated soils and aquifers although it does not have a fully credible reputation within the regulatory community.

Now to dispose different types of food waste that is eaten at college dining table, I will provide separate procedure to deal with:

Fruit and Vegetable Wastes

Fruits and vegetables are a very important part of the food industry especially in the Mediterranean countries where agriculture still remains one of the main sources of income. The fruit and vegetable canning industry, frozen vegetable industry, vegetable dehydration industry, fruit and vegetable drying industry, fruit pulping, tomato juice concentrate and fruit concentrate belong to this category. These industries may operate seasonally since operation time depends on the production of the fruits and vegetable that they process. That means that the environmental pollution from those industries’ waste will also be seasonal. According to the processing stage, different types of waste may be produced thus contributing with different percentages to the formation of the final process waste. The wastes from fruit and vegetable processing industries generally contain large amounts of solid suspensions and a high biochemical oxygen demand (BOD). Some other parameters usually of interest to the waste treatment are pH, chemical oxygen demand (COD), dissolved oxygen and total solids. Indicative values for BOD, COD, suspended solids (SS) and pH for the processing of some fruit and vegetables are summarized. As has already been described, fruit and vegetable industry wastes consist of various by-products with an acidic pH (Riggle 1989), and a moisture content of 80–90% . The chemical composition of the wastes varies and depends on the processed fruit or vegetable. In general, the wastes consist of hydrocarbons and relatively small amounts of proteins and fat. The hydrocarbons are mainly sugars and nitrogen and cellulose fibers. The water wastes contain dissolved compounds, pesticides, herbicides and cleaning chemicals. These differences in the nature of the wastes require their separate treatment. Although the solid waste is mainly treated with composting, because of superior results slurry 52 A. Punnagaiarasi et al. bioreactors and land farming may also constitute two further options. A pretreatment is necessary to remove the water and neutralize the pH to ensure the best conditions for microbial growth and development. Bulking agents are also added to improve the porosity of the sludge and decrease the bulk density . The increased porosity may help in the drainage of water, which can be carried out either by gravity or by exerting pressure on the sludge. In some investigations the waste was left in open air so that the excess water is evaporated . Aerated piles are more frequently used for the treatment of solid waste from fruit and vegetable industries because they allow the best mixing of the sludge while it is easy to add moisture, nutrients or more waste for processing if necessary. However, if static piles are initially used, then later the compost has to be moved to an aerated pile for further cure.

Fermentation Waste

Fermentable produts produces liquid waste with many common characteristics, such as high BODs and CODs, but differ in the concentration of the organic compounds that determine the biological treatment that will be selected. The difficulty in dealing with fermentable product wastewaters is in the flows and loads of the waste. Since the fermentable  wastewater contains high concentrations of tannins, phenols and organic acid, anaerobic treatment results in higher performance. attempted to compare aerobic with anaerobic treatment of the wastewaters in a German brewery. Anaerobic treatment achieved 91% COD reduction at loading rates up to 20 g COD/L day, whereas the aerobic treatment resulted in a 76% reduction at a loading rate of 69 g COD/L day. In order to optimize the conditions of anaerobic treatment, Suzuki et al. (1997) conducted several experiments for the optimization of acidity and temperature of highly concentrated brewery wastewater by applying the upflow anaerobic sludge blanket. These experiments showed that the optimal conditions for the particular treatment were 40 °C and 5–6 pH. The amount and load of distillery waste varies according to the raw materials used. In winery, the treatment methods are based on principles similar to the previous fermentation industries. Experiments conducted both in the laboratory and on industrial scale showed that with the use of a full-scale, modular, multi-stage activated sludge treatment plant could reduce the COD level up to 98% when the influent COD varies between 2000 and 9000 mg/L (Fumi et al. 1995). One of the main problems in winery waste treatment is the presence of vinasse (It is like a molasses, a hone like dark brown syrup), which needs to be treated biologically for 4–8 days in order to reduce 90% of the COD

Dairy Products

Dairy Products contribute substantially to the pollution of surface water and soil. The main wastes from these Products are chemically modified liquid wastes. The main characteristics of dairy waste can be summarized as follows: high organic load (fatty substances, etc.), large variations in waste supply, considerable variations in pH (4.2–9.4), relatively large load of suspended solids (SS) (400–2000 mg/L). The dairy wastewater may contain proteins, salts, fatty substances, lactose and various kinds of cleaning chemicals. Detergents represent the biggest portion of chemicals used in dairies. The detergents may be alkaline or acid and are used for different purposes. Hydroxides or alkaline salts are responsible for the alkalinity of the detergent. They are mainly added to dissolve and remove proteins, but they also help to eliminate fats through saponification. Sodium hydroxide is the most widely applied alkaline detergent but for special applications it may be replaced or mixed with other strong bases. Acids are used to remove the inorganic deposits or so-called milkstone. For that purpose, nitric acid or phosphoric acid are used separately or in combination. Both alkaline and acid detergents often contain additives to improve their cleaning capability. These are phosphates, sequestering agents, surfactants and some minor components like dispersing agents, anti-foaming agents and inhibitors (Romney 1990). The presence of detergents and their additives in dairy waste water hardly influences the total COD in contrast to milk, cream or whey. However, detergents also present difficulties in their treatment.

Meat and Poultry Products

Efficient utilization of meat by-products is important for the profitability of the meat industry. It has been estimated that 11.4% of the gross income from beef and 7.5% of the income from pork, come from the by-products. In the past, by products were a favourite food in Asia, but health concerns have led to an increased focus on non-food uses, such as pet foods, pharmaceuticals, cosmetics and animal feed . Meat by-products are produced by slaughter houses, meat processors, wholesalers and rendering plant. Traditional markets for edible meat by-products have gradually been disappearing because of low prices and health concerns. In response to these problems, meat processors have directed their marketing and research efforts towards non-food uses.

Pretreatment is also regarded as necessary for poultry waste to reduce the moisture and increase the porosity with the addition of bulking agents, which also increase the aeration and carbon level in wastewater. Proper treatment is needed to eliminate the pathogens.

Advantages of Bioremediation :-

• It conserves financial resources by the virtue of reduced cleanup times

• Capital expenditure is also less as compared to other remediation technologies (Geo Environmental 1998)

• This technology is widely accepted by industry as it maintains nature’s harmony • It destroys contaminants rather than transferring them from one medium into another.

Limitation of Bioremediation

• If the process is not controlled it is possible the organic contaminants may not be broken down fully resulting in toxic by-products that could be more mobile than the initial contamination.

• In the great majority of cases, an inoculation with specific microorganisms is neither necessary nor useful. Besides all these some other factors are also effect the bioremediation such as solubility of waste, nature and chemical composition of waste, oxidation—reduction potential of waste and microbial interaction with this. Hence the researchers should search genetically different type of microbes which can also work on slightly adverse condition. Therefore, bioremediation is still considered as a developing technology to regulate the day to day environmental problems faced by man residing in an area