Experimental Investigation on the Properties of Street and Sidewalk Cleaning Waste

“Waste from street and yard cleaning” has codes 20 03 03 and 20 03 06 “Sewer manhole cleaning waste” [1, 2]. The available literature does little to describe the properties of street and sidewalk cleaning waste. There is a knowledge gap in the literature related to the search for alternative management for municipal street and sidewalk cleaning waste in urban areas The sweepings contain numerous contaminants in the form of hydrocarbons, and heavy metals such as arsenic, mercury, lead, copper, cadmium, zinc, nickel, chromium, manganese. Pollutants from street sweeping can cause re-suspension of particles of various sizes PM 2.5 and PM 10 in the air these in turn cause high human exposure to heavy metals, metalloids and mineral substances [3, 4, 5]. Many articles have described the negative impact of road dust on human health, they increase the morbidity of people from various diseases, especially respiratory, allergies and dermatological diseases. Workers directly cleaning streets are particularly vulnerable [6, 7, 8]. According to the Central Statistical Office (CSO), total particulate matter (TSP) emissions in Poland in 2017 were about 2% higher than in 2016. Total particulate matter in 2017 came mainly from stationary combustion processes, including non-industrial combustion processes (about 45% of total emissions) [9, 10]. Emissions from road transport and other vehicles and equipment (including rail transport) accounted for about 10% of national TSP emissions [11, 12, 13] A significant portion of emissions in this category came from processes other than fuel combustion, i.e. tire and brake abrasion and road surface abrasion. Year after year, road dust is increasing [14, 15]. The impact of fine particles (PM 10) and very fine particles below PM 2.5 of total particulate matter on human health depends on the size of these particles and their chemical composition [16, 17, 18]. PM 2.5 and smaller, has the ability to penetrate the deepest parts of the lungs, where it is accumulated or dissolved in biological fluids and then transported throughout the body with the bloodstream [19, 20]. Due to the negative impact of PM 2.5 on human health, additional standards have been introduced, air quality for urban background areas in cities with more than 100,000 inhabitants and agglomerations EP Directive on, Air Quality and Cleaner Air for Europe 21, 22, 23, 24]. Street and sidewalk cleaning waste is a major health problem due to particulate matter. An economic problem because of the cost of disposal, as well as a big problem for a closed-loop economy because there is no technology to manage it [25, 26], it is dumped in landfills which is a big environmental and economic burden [27]. Through the lack of closed-loop management technology, it generates very high economic and environmental costs. The permissible standards for waste to be landfilled according to the Ordinance of the Minister of Economy of July 16, 2015 on allowing waste to be landfilled are very strict. The total organic carbon in this waste must not exceed 5% of dry weight, the roasting loss must not exceed 8% of dry weight and the heat of combustion must not exceed 6 MJ/kg of dry weight [28, 29, 30]. Therefore, a systematic examination of the waste for these parameters is an important aspect.

Samples for scavenging were taken in a medium-sized city with a population of about 58,000, rich in heavy industry, armaments and aluminium processing. Street and sidewalk cleaning waste in the region had not been subjected to any previous testing. Street cleaning waste was sampled from containers located in sweeping trucks, while sidewalk waste was sampled directly. Samples were taken from the sidewalk and three streets labellel, Streets 1, Streets 2, Streets 3 and Sidewalk. The sampling time for all samples lasted 4 weeks and took place at the end of summer. Waste was collected using a collection method based on the standard: Urban waste disposal – Collection, storage and transfer, and initial preparation of waste samples for testing [31, 32]. First, primary samples were taken, followed by an intermediate sample from them. Representative samples were transported to the laboratory for further processing and detailed testing, i.e.: moisture content, organic and mineral content.

Due to the high moisture content of the waste resulting from the use of water for street cleaning during sweeping, the first test was to determine the water content based on PN-93/Z-15008/01, PN-93/Z-15008/02 [34, 35] and thus dry the waste in a laboratory dryer. The next step, was to determine the content of mineral and organic fractions and determine the stability and repeatability of the proportion of these fractions in the waste. The next step was to determine the fractionality of the waste using a laboratory shaker to determine the overall size of the waste in each frac

Due to the presence of water in the sweepings, they were subjected to a drying process in a laboratory dryer. In carrying out this process, the Polish Standards were relied upon: PN-93/Z-15008/01 [33, 34] Municipal solid waste. Testing of fuel properties. General provisions. PN-93/Z15008/02 [34]. Municipal solid waste. Tests of fuel properties. Determination of total moisture content. The dry matter and water content of sweepings are shown in Table 1.

Water and dry matter contents were examined summatively in large bins for a large sample by weight. The data obtained show comparable values for water content in the three samples taken from each site. In the samples named Street 1 and Sidewalk, the water content is about 13%. In the sample named Street 2, the water content is about 18%. Only in the sample labelled, Street 3, is the water content higher, at about 28%.

Determination of the mineral content of street and sidewalk cleaning waste Figure 1 below shows the average results obtained from 30 samples of the test of the mineral and organic part in street and sidewalk cleaning waste, based on the Polish Standard: PN-93/Z-15008/01 [34] Municipal solid waste. Testing of fuel properties. General provisions and PN-93/Z-15008/03 [35] Municipal solid waste. Tests of fuel properties. Determination of the content of combustible and noncombustible parts.

Figure 1.

In all the samples taken from different sites, the mineral fraction is at a level of more than 90%. This indicates the stability of this waste in terms of mineral fraction and organic fraction.

The highest mineral fraction is in the Streets 1 sample, this is a sample taken from a busy street. The mineral fraction content is similar in the Streets 3 and Sidewalk samples, these are less busy places, rich in vegetation surroundings. The mineral fraction content of the Streets 2 sample ranks among the other sampling sites, it is a medium traffic site.

Due to the lack of previous studies conducted in this region for this waste, it was decided to examine it additionally in terms of the size of the fraction and the most pleasant particles present. A laboratory shaker was used to evaluate the fractional size of this waste. Sieves of 10 mm; 2 mm; 0.05 mm were installed in it. The appropriate amplitude and frequency were set to enable the waste to be thoroughly sieved. Photos and results of this analysis are presented below.

Comparing the fractional distribution of the different samples shown in Table 2 above, one can see a relationship. If a given sample comes from a site with a lot of trees and shrubs Streets 3 and Sidewalk, it will inevitably contain a lot of sticks, leaves or seeds from these plants. In these samples, you can see the retention of these organics on the 10 mm sieve. On the other hand the amount of mineral part in these samples under the 0.05 mm sieve is 1.81% and 2.48% is a smaller amount when comparing them with the samples that come from the busy tree-poor sites Streets 1 and Streets 2, where the content of organics on the 10 mm sieve is small, while the content of mineral part under the 0.05 mm sieve is higher at 2.92% and 4.58%. The largest amount by weight in all samples is the fraction retained on the 0.05 mm sieve. This is mainly a mineral fraction, but in samples from areas rich in trees and shrubs, retention of fine organics is observed in this fraction.

Figure 2.

Street and sidewalk cleaning waste is a certain environmental ballast, mainly because to date there is a lack of ways and technologies to recover and recycle it, so it is landfilled in non-hazardous and inert waste landfills, generating costs and taking up space in landfills. Such handling is incompatible with the philosophy of circular economy. Through the lack of closed-loop management technology, it generates very high economic and environmental costs. Tests conducted in the paper on the water content and the mineral and organic fractions for this waste proved that, according to the law, the content of organic parts exceeds the 5% organic carbon limit as acceptable for landfilling. Therefore, there is a need for further research on this waste, for example, on particle size or PAH content. It is also worth focusing on the search for new management methods for it in accordance with the circular economy.