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Article

The Influence of Pandemic Lockdowns on Municipal Wastewater Quality as a Consequence of Not Discharging Food Waste from Restaurants

by
Joanna Rodziewicz
1,
Jarosław Pesta
2,
Wojciech Janczukowicz
1 and
Artur Mielcarek
1,*
1
Department of Environment Engineering, University of Warmia and Mazury in Olsztyn, Warszawska 117a, 10-719 Olsztyn, Poland
2
ZWiK Sp. z o.o. in Mikołajki, Dąbrowski 7, 11-730 Mikołajki, Poland
*
Author to whom correspondence should be addressed.
Appl. Sci. 2023, 13(15), 8875; https://doi.org/10.3390/app13158875
Submission received: 6 July 2023 / Revised: 28 July 2023 / Accepted: 30 July 2023 / Published: 1 August 2023
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Abstract

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The results of this research show the scale of the environmental problem related to the discharge of shredded solid waste from catering facilities to the sewage network and wastewater treatment plants. The study results indicate the viability of implementing a system for managing food waste from catering facilities in tourist towns. The basic and initial element of this system would be the collection of food waste from catering facilities and its processing in closed digesters on the premises of the treatment plant in order to produce methane, which can be used for heating and energy purposes. At the same time, electricity consumption at wastewater treatment plants will decrease due to lower pollutant loads in sewage flowing to the treatment plant, thereby reducing the carbon and nitrogen footprint of purification.

Abstract

The use of food waste disposers in gastronomical facilities influences municipal wastewater composition. Ground food waste poses problems in the operation of the sewerage network and generates high electric energy consumption in wastewater treatment plants (WWTPs). This study aimed to determine, for five towns with a PE (Population Equivalent) ranging from 4000 to 220,000, the volumes of catering waste discharged to the WWTPs. The towns differed in the number of inhabitants, beds in hotels, and catering places. The calculations were undertaken based on data received from the operators of the WWTPs. The pollutant concentrations in 2019 were compared with data from the “pandemic” year—2020. The loads of catering waste entering the sewerage system in 2019 ranged from 32.7 to 1062 tons. In the town with the largest tourist base, the BOD (Biochemical Oxygen Demand) value in 2020 accounted for 62.3% of the 2019 value. In the largest town, the annual energy consumption for food waste treatment could be up to 2,539,770 kWh. If the waste was fermented, up to 1,376,650 m3 of methane could be obtained. There is a strong need to implement a collection system for food waste from catering facilities, and the fermentation of this waste to produce methane, which can be used for energy purposes.

1. Introduction

The operators of wastewater treatment plants in Poland have been observing an increase in the concentration of raw sewage for several years, in particular considering organic substances [1]. This is because of water consumption reduction, restoration of the sewerage networks, growing wealth, and huge wastage of food. The use of colloid mills in gastronomical facilities poses severe, adverse effects that influence the municipal wastewater composition, especially in tourist destinations. The change in lifestyle has resulted in the intensive development of gastronomic establishments, which in 2019 were visited by 93% of the Poles, compared to only 33% recorded in 2014 [2].
The problem of food waste management remains unresolved across the world. This applies to waste from the agri-food industry, gastronomy facilities, and households. It should be borne in mind that the EU Directive on the landfill of waste enforces the reduction in the amount of waste discharged to landfills in order to reduce methane emissions into the atmosphere [3]. It is estimated that approximately 3.3 billion tons of CO2, which is the major greenhouse gas, are released into the atmosphere annually as a result of waste biodegradation [4]. However, other solutions that are alternatives to discharging waste to landfills are possible. For example, many researchers aim to mitigate food waste by turning it into value-added products [5,6,7].
From the logistical perspective, the most difficult type of waste to manage is that originating from households. It is usually dealt with via three approaches. First of all, it ends up in mixed municipal waste and is deposited in landfills, contributing to environmental pollution with carbon dioxide. The Food and Agriculture Organization of the United Nations (FAO) reports that 1 billion, 300 million tons of edible food are wasted in the world every year. In Poland, almost 5 million tons of food are wasted annually (more than half of which derives not from trade and gastronomy facilities, but from households); in the UK, in 2006, this figure was approximately 6.7 million tons [3], whereas 39.7 million tons of food waste are landfilled annually in the US [8].
The second approach is related to the use of home composters but is primarily limited to single-family housing. However, the scale of this solution is fairly limited [8].
The third solution, practically absent in Poland, is based on the use of food waste disposers (FWDs) in the kitchens of residential buildings. This is a controversial solution because it is associated with a large amount of highly concentrated wastewater, an increased amount of sludge generated in wastewater treatment plants, increased wastewater treatment costs (energy consumption in particular), and an increase in water consumption in the households applying FWDs. The use of FWDs in households is prohibited in many countries, such as Belgium, the Netherlands, or Austria. In contrast, they are sold to households with or without restrictions in around 50 countries, including England, Ireland, Italy, Spain, Japan, Canada, Mexico, and Australia. In the USA, approximately 50% of households have an FWD installed [9].
On the other hand, there are arguments that the use of FWDs can be beneficial, because it reduces the amount of food waste generated by 42%, thereby reducing the costs of its disposal [10]. Ground food waste discharged with sewage to the municipal wastewater treatment plant increases the concentration of organic matter in the sludge, which increases biogas production [11]. Research by Thomas [3] showed that household food waste ground in an FWD had COD (Chemical Oxygen Demand) values ranging from 10,600 to 28,600 mg/L and BOD values in the range from 4760 to 13,700 mg/L. It also needs to be emphasized that 40% of COD and 30% of nitrogen present in wastewater were in the soluble form [12].
In addition, the use of FWDs results in the generation of larger volumes of sludge and sewage, as well as higher energy consumption and a greater demand for water. The BOD load in influents entering the wastewater treatment plant may increase by 17–62%, and that of total suspended solids by 1.9–7.1%. A total of 11.7 L of water is needed to prepare and drain 1 kg of food waste [9].
Research by Maalouf and El-Fadel [11] showed that the use of FWDs in a developing economy characterized by a high share of food waste can be an alternative solution to reducing emissions in emissions trading. Experimental results demonstrated a reduction in emissions of approximately 42%, with savings of up to 28%, taking into account environmental external factors, including sludge management.
In the case of waste generated in catering facilities, it is possible to develop and implement a system that will enable exploiting its energy potential and, at the same time, minimize problems and costs associated with the operation of the sewerage system and wastewater treatment plants. This should be the case because European regulations urge the pursuit of such solutions. As a result of implementing EU legislation, feeding livestock with food waste is strictly prohibited [13]. Food waste from restaurants must be stored in properly maintained containers and then forwarded to the entrepreneur acting on the basis of the Waste Act [14]. However, such activities are labor intensive. Food waste from restaurants, bars, cafeterias, etc. is commonly ground and discharged to the sewerage system, despite the fact that it is prohibited in the EU (including Poland). This treatment of food waste is against provisions of the Act on collective water supply and collective sewage disposal [15]. Wastewater generated in restaurants has high concentrations of total suspended solids, BOD, COD, and contents of fat and oil [16]. The volumes and composition of wastewater generated in restaurants depend on the restaurant type (i.e., Italian, Chinese, Indian, etc.), kitchen size, the time of served meals, the category of meals, and restaurant size. Qualitative studies of food waste generated in catering facilities conducted in Korea and the USA (Table 1) showed that the percentage share of organic substances in this type of waste was 95 and 85.3%, respectively.
Ground food waste generates substantial costs, especially due to high electric energy consumption in WWTPs [3,19]. The scale of the problem is evidenced by the results of research on waste from academic canteens that was ground in mills, whose COD ranged from 500,000 to 2,000,000 g O2/m3 [20].
The severity of the problem is also indicated by the quantities of hardly biodegradable pollutants, such as fats and oils, which are present in large quantities in catering wastewater. Their concentration was even up to 6500 mg/L (Table 2). On the other hand, this proves the high energy potential of this wastewater [21].
It can be expected that food waste will significantly change the proportions of organic and biogenic compounds in wastewater inflowing to the treatment plant. Table 3 presents data on the ratio of organic compounds and nitrogen compounds (C/N) in the catering waste. This ratio exceeds the value of 14, which proves that the waste could serve as a source of carbon in denitrification and dephosphatation processes for wastewater that is poor in organic compounds.
This means that the surplus of the organic substrate present in the waste that exceeds the needs of denitrifying bacteria (C/N ratio should range from 1 to 5) can be exploited in the dephosphatation process [28]. It is obvious that food waste from restaurants, bars, cafeterias, etc. should be collected. Strict law enforcement and the construction of an effective system are required for its collection. Due to the content of organic substances, it can be used after being fermented in VFA (Volatile Fatty Acid) generators as an external carbon source in the processes of denitrification and dephosphatation. The next rational solution is fermentation with sewage sludge, which would increase the quantity of biogas and the revenues of WWTPs [29]. Another solution could be the discharge of food waste to a biogas plant.
As a result of the COVID-19 pandemic, restaurants, bars, hotels, and other gastronomic and accommodation businesses were closed many times in 2020 and 2021, limiting the production of meals and ground restaurant food waste. This affected the concentration of municipal wastewater. Studies on the quality of wastewater in the period before, during, and after the pandemic allowed the determination of the scale of the impact of restaurant wastewater on the quality of urban wastewater, especially in tourist towns.
The aim of this study was to demonstrate the influence of pandemic lockdowns on wastewater quality, because of the discharge of less food waste into sewage pipes, and to determine the scale of the environmental problem of discharging food waste from restaurants to municipal sewerage systems.
The scope of the present study included determination of the load of catering waste discharged to the wastewater treatment plant, determination of the increase in sewage concentration resulting from the discharge of fragmented food waste, and determination of the scale of the increase in pollutant loads of organic compounds, suspended solids, and biogenes. In addition, the amount of methane that could be generated via anaerobic digestion from catering waste and the consumption of electricity in WWTPs for aerobic neutralization of organic compounds from food waste ground in FWDs were estimated.

2. Materials and Methods

The study analyzed the results of investigations on wastewater concentrations flowing into the wastewater treatment plants (WWTPs) in 5 towns in Poland (A, B, C, D, E), differing in size and tourist attractiveness. The towns are characterized by the number of inhabitants, hotel beds, and food places (Table 4).
Among them, there are typical tourist towns (A, B, D) and towns with a tourist sector of various importance in the local economy. The results were compiled from whole-year data provided by local municipal water and sewage companies. The scope of the research included determinations of the concentration of COD (spectrophotometric method, [30]), BOD (optical method, [31]), suspended solids (SS, weight method, PN-EN 872:2007+Ap1:2007), total nitrogen (TN, spectrophotometric method, PBL/S-09 3rd edition, based on Merck cuvette test 1.14537.0001), and total phosphorus (TP, spectrophotometric method, PBL/S-07 5th edition, based on Merck cuvette test 1.14543.0001, 1.14729.0001) in the years 2019–2021.
Physicochemical analyzes of sewage were performed by accredited laboratories. The number of samples analyzed, based on which the average values were calculated, ranged from 38 (A) to 110 (E).
In town E, despite the fact that it has a separate sewerage system, rainwater enters the network during heavy rainfall and spring thaws. At the same time, other towns are being connected to the network within the established agglomeration. These may be the reasons for the increased flows recorded in this town in 2020 and 2021 (Table 4). Due to the pandemic, hotels and gastronomic businesses were closed many times in 2020 and 2021, limiting the production of meals. In Poland, the lockdown schedule was as follows:
  • restaurants:
13 March 2020–18 May 2020
23 October 2020–3 May 2021
  • hotels:
31 March 2020–4 May 2020
7 October 2020–3 May 2021
Since the facilities were closed for more than 5 months, it may be speculated that the amounts of catering waste were higher than those presented in the publication. However, it should be remembered that the end of the lockdown does not mean the immediate opening of catering facilities and hotels. This takes time. Therefore, the mean values of pollutant concentrations were calculated on the basis of data for the whole year.

3. Results and Discussion

In all analyzed towns, similar trends were observed in respect of the BOD concentration of sewage flowing into the treatment plant (Figure 1).
The highest values of this indicator were recorded in 2019, and the lowest in 2020, when catering and hotel facilities were closed many times. In 2021, the BOD concentrations of sewage from the largest towns studied (D and E) returned to levels similar to those of 2019. On the other hand, in smaller towns (A, B, C) with greater importance of tourist facilities, the BOD concentration recorded in 2021 was higher than in 2020 but lower than in 2019. This was due to the restrictions on the operation of catering and hotel facilities in the first four months of 2021 and the “slowdown in tourist traffic” observed around the world during the COVID-19 pandemic [32].
The scale of the problem is most evident in the example of town A, which is an exclusively tourist destination (Table 4), as indicated by the number of beds in hotel facilities per 1000 inhabitants (375) and the number of places where meals are served (13). In this town, the closing of tourist and catering facilities was observed to have a significant impact on the concentration of organic compounds in sewage discharged to the treatment plant. The BOD and COD values (Figure 2) in 2020 accounted for 62.3% and 66.4%, respectively, of the values recorded in the year preceding the pandemic (2019).
The annual load of pollutants discharged to the treatment plant in 2020 (Table 5) amounted to 169,159 kg BOD/year and was lower by 131,702 kg BOD compared to 2019 (300,861 kg BOD/year).
Similarly large changes were recorded in town C, where BOD and COD concentrations recorded in 2020 accounted for 52.8% and 51.5%, respectively, of the values recorded in the year preceding the pandemic (2019). Here, the annual load of pollutants entering the wastewater treatment plant in 2020 (Table 5) was 191,902 kg BOD/year, which was 217,595 kg BOD lower than in 2019 (409,498 kg BOD/year). This difference was due to the closure of the border crossing due to COVID-19 and the dramatic reduction in the number of people entering this city, which is the first border town.
Remarkably smaller differences between BOD and COD concentrations in 2019 and 2020 were observed in towns B, D, and E. Therefore, in town B, the average BOD of sewage was lower in 2020 than the corresponding value recorded in 2019 by 42 g O2/m3, and that of COD by 117 g O2/m3.
In town D, the differences were 52 and 78 g O2/m3, respectively. In the case of the largest town, E, the differences in pollutant concentrations were 73 and 45 g O2/m3, respectively.
Despite the fact that the recorded differences between the pollutant concentrations in towns B, D, and E were smaller than those in towns A and C, when taking into account the annual loads of organic pollutants expressed by the BOD indicator in towns B, D, and E, the differences between 2019 and 2020 were significant and amounted to 19,000 kg O2/year, 158,000 kg O2/year, and 616,000 kg O2/year, respectively. The COD values determined for towns B and D were 110,000 kg O2/year and 253,000 kg O2/year, respectively, whereas the load of COD pollutants received at the wastewater treatment plant in town E in 2020 was 144,000 kg O2/year lower than in 2019, which was primarily due to the higher average daily flows of influents.
Similar trends were noted for total suspended solids (Figure 3). In towns A and C, their concentration determined in sewage in 2020 was about 45% of the values recorded in 2019. In towns D and E, these differences were minimal. In town B, the concentration of suspended solids accounted for 86% of the value recorded in 2019.
In towns A, B and C, the total nitrogen concentration determined in 2020 was from 81 to 86% of the 2019 value (Figure 4). In town D, it was similar, as it was 1 g/m3 higher than in 2019 (92 and 93 g/m3, respectively), whereas in town E it accounted for 90% of the 2019 value.
The pandemic period and the resulting lockdowns of catering facilities had the least effect on phosphorus concentration in raw sewage (Figure 5). In towns D and E, its values were the same in both years. In town A, in 2020, the concentration of phosphorus was 1 g/m3 higher than in 2019 (10 and 11 g/m3, respectively). In town B, its concentration recorded in 2020 accounted for 90% of the 2019 value, whereas in town C it accounted for 78%.
Based on literature data, it is possible to estimate the volume of food waste discharged to the sewerage system in 2019. This was primarily waste from catering facilities, because, in practice, FWDs are not used in individual households in Poland. According to the literature, one gram of dry food waste generates 1.21 g of COD, 0.58 g of BOD, 0.36 g of total suspended solids, 0.025 g of total nitrogen, and 0.013 g of total phosphorus [12]. Calculations made based on the BOD values show that about 227,600 kg of dry matter of food waste was discharged into the sewerage system throughout the year in the smallest town (town A). In town C, it was as much as approximately 374,150 kg of food waste. In the largest town studied, the annual amount of food waste discharged into the sewerage system exceeded 1 million kg (Table 6).
A system for the collection of food waste from restaurants and other facilities for mass catering, and the transfer of this waste to facilities for the anaerobic disposal of solid waste, could be a viable means for the production of methane-rich biogas. According to Lelicińska-Serafin et al. [33], waste from Polish catering facilities contains an average of 87.82 ± 4.05% VS. The values of the potential methane production parameter, which for catering food waste are in the range of 216–1476 L/kg VS [33], enable the volume of methane that can be produced during this waste digestion to be established.
For the potential methane production of 216 L/kg VS, these values are 43,170 m3/year, 70,970 m3/year, and 201,460 m3/year for towns A, C, and E, respectively. Considering the upper value of the parameter (1476 L/kg VS), the respective values would be 295,000, 484,980, and 1,376,650 m3 methane/year, respectively (Table 6).
The discharge of wastewater from food service (catering) facilities to the sewerage system has certain consequences in terms of energy consumption. Organic pollutants contained in food waste must be neutralized in the process of aerobic biotreatment. The introduction of oxygen into the activated sludge chambers entails electricity consumption.
The amount of energy used to this end was determined based on the value of the indicator showing the amount of energy consumption (kWh) per 1 kg of the BOD load removed (kWh/kgBODrem.). According to literature data, the values of this indicator range from 0.533 to 4.34 kWh/kgBODrem. [34,35]. In order to calculate the volume of load removed, the efficiency of BOD removal was assumed to be 95%. The results of the calculations are presented in Table 6.
If the system for the collection of food waste from restaurants and other facilities for mass catering was in operation in town A, then the energy consumption recorded in its wastewater treatment plant in 2019 would be lower by 66,400 kWh (for a specific energy consumption of 0.533 kW/kg BODrem.) or by 544,240 kWh (for a specific energy consumption of 4.34 kW/kg BODrem.). In town C, these values would amount to 109,800 and 894,690 kWh/year, respectively. In turn, energy savings in town E would range from 311,700 to 2,539,770 kWh/year.
The values presented above indicate a very strong need to introduce a system for collecting food waste from catering facilities and delivering it to sludge facilities at the wastewater treatment plants. On the one hand, implementation of this solution is expected to ensure a significant reduction in electricity consumption for the aerobic treatment of wastewater in treatment plants, a probable improvement in the quality of treated wastewater, a reduction in the amount of sewage sludge generated, and a reduction in the cost of its treatment. In addition, more biogas will be produced in sludge and waste fermentation facilities. On the expenditure side, there will be costs of implementing and maintaining a food waste collection system and increased costs of its processing in closed digesters. Taking into account the results of the calculations, it can be envisaged that the revenues and savings resulting from the implementation of the system will significantly exceed the expected costs.
The implementation of a food waste collection system from catering facilities should underlie changes in the approach to food waste in entire towns. The next step should be to introduce a management system for this type of waste, including multi-family blocks of flats and single-family houses.

4. Conclusions

The problem of utilizing the energy potential of food waste and the generation of unjustified costs due to the disposal of food waste in wastewater treatment plants is a global issue. This applies to both household and catering facilities. In the latter, the main viable solution is the use of FWDs, which are common in gastronomy facilities in Poland, but are practically absent in private houses and flats.
The study aimed to determine, based on the example of five towns with a PE ranging from 4000 to 220,000, the volumes of catering waste discharged to the sewerage system and then to the wastewater treatment plants. The towns differed not only in the number of inhabitants, but, above all, in the size of the hotel and catering base.
The extent of the increase in the concentration of wastewater resulting from the discharge of fragmented WF to the sewerage system, as well as the scale of the increase in the load of pollutants of organic compounds, suspended solids, and biogenes, were also determined. In the analyzed towns, the loads of catering waste entering the sewerage system in 2019 ranged from 32.7 to 1062 tons. In addition, the amount of methane that could be generated during anaerobic digestion of catering waste and the increased consumption of electricity in wastewater treatment plants in facilities for aerobic neutralization of organic compounds from food waste ground in FWDs were estimated.
The calculations were undertaken based on data received from the operators of the treatment plants in 2019–2020. The pollutant concentrations in wastewater before the COVID-19 pandemic, i.e., in 2019, were compared with data from the “pandemic” year, 2020, when, as a result of lockdowns, most hotel and catering facilities in Poland were closed for many months. Since the facilities were closed for more than 5 months, it can be assumed that the amounts of catering waste were higher than those presented in the publication. However, it should be remembered that the end of the lockdown does not mean the immediate opening of catering facilities and hotels.
The research showed that in the towns that are more attractive from a tourist perspective (towns A and C), COVID-19 contributed to a noticeable reduction in the concentration of sewage flowing into the treatment plants. In town A, which has the largest tourist base, the BOD and COD values in 2020 accounted for 62.3% and 66.4%, respectively, of the values recorded in the year preceding the pandemic, while the annual load of pollutants flowing into the treatment plant in 2020 was 131,702 kg BOD lower than the load in 2019. At the same time, in larger towns (D and E), due to much higher annual flows, the load of pollutants resulting from grinding food waste and discharging it to the sewerage system caused very high energy costs in wastewater treatment plants. In the case of the largest town studied (220,000 PE), the annual energy consumption for food waste treatment ranged from 311,700 to 2,539,770 kWh. If, instead of being discharged to the sewerage system, the waste was delivered to facilities intended for anaerobic solid waste fermentation, it would be possible to produce a volume of methane ranging from 201,460 to 1,376,650 m3.
The study results indicate the viability of implementing a system for managing food waste from catering facilities in Poland. The basic and initial element of this system would be the collection of food waste from catering facilities and its processing in closed digesters on the premises of the treatment plant in order to produce methane, which could be used for heating and energy purposes. Another future-oriented action would be the introduction of a household food waste management system.

Author Contributions

Conceptualization, W.J.; methodology, J.R. and J.P.; validation, W.J. and A.M.; formal analysis, W.J., J.R. and J.P.; investigation, J.R., W.J. and A.M.; resources, W.J. and J.R.; data curation, J.R.; writing—original draft preparation, J.R., W.J., J.P. and A.M.; writing—review and editing, A.M. and W.J.; visualization, J.R. and J.P.; supervision, W.J. and J.R.; project administration, J.R.; funding acquisition, J.R. and W.J. All authors have read and agreed to the published version of the manuscript.

Funding

The study was financially co-supported in the framework of a Project no. 29.610.023-300 of the University of Warmia and Mazury in Olsztyn, Poland.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Acknowledgments

The article was created under Project no. POWR.03.05.00-00-Z310/17: “Development Program of the University of Warmia and Mazury in Olsztyn”.

Conflicts of Interest

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

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Applsci 13 08875 g001 550
Figure 1. Average BOD concentration of raw wastewater in 2019–2021.
Figure 1. Average BOD concentration of raw wastewater in 2019–2021.
Applsci 13 08875 g001
Applsci 13 08875 g002 550
Figure 2. Average COD concentration of raw wastewater in 2019–2021.
Figure 2. Average COD concentration of raw wastewater in 2019–2021.
Applsci 13 08875 g002
Applsci 13 08875 g003 550
Figure 3. Average suspended solids concentration of raw wastewater in 2019–2021.
Figure 3. Average suspended solids concentration of raw wastewater in 2019–2021.
Applsci 13 08875 g003
Applsci 13 08875 g004 550
Figure 4. Average nitrogen concentration of raw wastewater in 2019–2021.
Figure 4. Average nitrogen concentration of raw wastewater in 2019–2021.
Applsci 13 08875 g004
Applsci 13 08875 g005 550
Figure 5. Average phosphorus concentration of raw wastewater in 2019–2021.
Figure 5. Average phosphorus concentration of raw wastewater in 2019–2021.
Applsci 13 08875 g005
Table
Table 1. Characteristics of food waste (data from Korea [17]; * data from USA [18]).
Table 1. Characteristics of food waste (data from Korea [17]; * data from USA [18]).
ParameterUnitValue
Physical properties
  • density
  • humidity
  • dry matter (DM)
  • volatile substances
  • volatile substances /dry matter

g/L
%
g/L
g/L
-
502.2
79.5 (69.1 *)
391.3
371.7
0.95 (85.3 *)
Ingredients
  • grains (with dimensions below 10 mm)
  • vegetables (less than 30 mm)
  • meat (less than 20 mm)
% DM
% DM
% DM		61.1
29.7
9.2
elementary analysis
carbon, C
hydrogen, H
oxygen, O
nitrogen, N
phosphorus, P
sulfur, S
C/N
% DM
% DM
% DM
% DM
% DM
% DM

51.4 (46.78 *)
6.1
38.9
3.5 (3.16 *)
0.52 *
0.1
14.7
Table
Table 2. Characteristics of food waste [18].
Table 2. Characteristics of food waste [18].
Restaurant TypeFat Concentration (mg/L)
Chicken fryer120–6500
Chinese76–1300
Mexican96–1040
Pub130–706
Table
Table 3. Characteristics of catering and food waste depending on the place of origin.
Table 3. Characteristics of catering and food waste depending on the place of origin.
SourcePropertiesCountryLiterature Item
Humidity %Volatile Substances/
Dry Matter, %		C/N
Dining room809514.7Korea[17]
University canteen8094-Korea[22]
Dining room 939418.3Korea[23]
Dining room8496-Korea[24]
Urban food waste9080-Germany[25]
Urban food waste7490–9736.4Australia[26]
Fruit and vegetable waste8589-India[27]
Catering and food waste748714.8USA[18]
Table
Table 4. Characteristics of the towns that are the subject of the research.
Table 4. Characteristics of the towns that are the subject of the research.
TownAreaPopulationBeds in HotelsBeds in HotelsFood
Places		Average Daily Flow
201920202021
km2PENumberNumber/
1000 PE		Places/
1000 PE		m3/d
A8.854000150037513.00127411501224
B10.8711,000383353.20184517572064
C11.7922,000230100.91268423793434
D13.7233,0001160351.30693168197167
E88.33220,0005200242.0436,00038,00041,000
Table
Table 5. Pollution loads in 2019–2021.
Table 5. Pollution loads in 2019–2021.
Parameter
g/m3		Load, 103·kg/YearLoad, 103·kg/YearLoad, 103·kg/Year
201920202021
ABCDEABCDEABCDE
BOD301211409181671351691921921658651920526132218607752
COD642737827366813,823384627377341513,967293800591377515,100
SS23138232116276872973121261551703220338221316517602
TN4062842321301305148231124840621012491406
TP5139351844116351945131037224
Table
Table 6. Potential energy benefits resulting from the introduction of a food waste collection system in towns A, B, C, D, and E and the disposal of the waste in digesters.
Table 6. Potential energy benefits resulting from the introduction of a food waste collection system in towns A, B, C, D, and E and the disposal of the waste in digesters.
Amount of Food Waste from Gastronomy Facilities,
kg/Year		The Amount of Methane That Can Be Generated from Catering Waste, m3Annual Amount of Energy Used during the Cleaning Process, kWh/Rok
216 L/kg VS1476 L/kg VS0.533
kWh/kgBODrem		4.34
kWh/kgBODrem.
A227,60043,170295,00066,400544,240
B32,750620042,450961078,340
C374,15070,970484,980109,800894,690
D272,40051,670353,09079,950651,430
E1,062,050201,4601,376,650311,7002,539,770
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Rodziewicz, J.; Pesta, J.; Janczukowicz, W.; Mielcarek, A. The Influence of Pandemic Lockdowns on Municipal Wastewater Quality as a Consequence of Not Discharging Food Waste from Restaurants. Appl. Sci. 2023, 13, 8875. https://doi.org/10.3390/app13158875

AMA Style

Rodziewicz J, Pesta J, Janczukowicz W, Mielcarek A. The Influence of Pandemic Lockdowns on Municipal Wastewater Quality as a Consequence of Not Discharging Food Waste from Restaurants. Applied Sciences. 2023; 13(15):8875. https://doi.org/10.3390/app13158875

Chicago/Turabian Style

Rodziewicz, Joanna, Jarosław Pesta, Wojciech Janczukowicz, and Artur Mielcarek. 2023. "The Influence of Pandemic Lockdowns on Municipal Wastewater Quality as a Consequence of Not Discharging Food Waste from Restaurants" Applied Sciences 13, no. 15: 8875. https://doi.org/10.3390/app13158875

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