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In order to draw meaningful conclusions from the results of the experimentation with the wastewater sample collected from the Wervershoof WWTP, it is necessary to determine if the sample was representative of the typical effluent. The water quality data from the sample used in the IHE bench scale experiments can be compared to historic water quality parameters of the Wervershoof WWTP effluent to accomplish this. The sample used in this research, which was a 24-hour sample collected from March 14-15th_,

can be compared to the general water quality characteristics of the effluent over time to determine if it is representative of the effluent water quality as a whole. Over the course of the 6-month research period, monthly samples of the treatment plant effluent were collected and sent for lab analysis for several water quality tests. These tests yielded data for basic water quality parameters such as; BOD5, COD, TKN, NH4, NO2, NO3, Total N,

PO4, and oxygen consumption. In addition to the monthly tests analyzed in the lab,

weekly analysis of the effluent was performed onsite. These weekly tests consisted mainly of temperature readings, UVT, and nitrite-nitrate tests.

The main purpose of the monthly tests was to determine to what degree the water quality parameters of the wastewater effluent varied over the 6-month period.

Representativeness was determined by first calculating the mean for each water quality parameter during each month of the 6-month sampling period, including March. A comprehensive mean for all available data of the 6-month period was then calculated for each water quality parameter. Additionally, for the 6-month period set a standard

for the degree of variability from the mean to be determined for each of the water quality parameters during the sampling period, this is of specific interest in the month of March when the sample for this research was collected.

Several water quality parameters are of notable interest, due to their effect on providing ozone demand in the wastewater, such as COD, BOD5 and NH4. The month of

March exhibits concentrations of COD, TKN, NH4, NO2, NO3, total nitrogen and total

phosphorus that are within one standard deviation of the average for the 6-month period. Data within one standard deviation of the 6-month mean shows the data’s low degree of variability. This lack of variability from the mean exhibits that the water quality data (COD, TKN, NH4 etc.) from March does not deviate greatly from the 6-month mean, and

therefore is representative of the overall wastewater characteristics.

To further ensure that the sample used during this research is representative, the 500L sample was collected over a 24-hour period using a continuous flow pump. With a continuously pumped 24-hour sample all daily variations of contaminant and OMP inputs to the plant are captured in the sample.

Treatment Plant Analyte

BOD5 (mg/l) COD (mg/l) NH4-N (mg/l) NOX-N (mg/l) P Total (mg/l) N Total (mg/l) PO4 3- (mg/l)

Wervershoof 3.6 +/- 0.8 36.5 +/- 3.4 4.4 +/- 1.6 2.1 +/-0.4 0.3 +/- 0.1 8.4 +/- 1.8 0.1 +/- 0.06

Table 33: Wastewater effluent data for the Wervershoof WWTP, 6-month average and standard deviation

To determine the level of representation the sample taken from March 14-15th _{has in}

regards to the overall Wervershoof effluent, several comparisons can be made. While limited water quality data exists for the day the sample was taken, parallels can be made to the day prior to sampling, when water quality analysis of the effluent was performed.

The day before the 24 hour sample was taken, March 13th_{, there is available data}

for the general water quality characteristics of the secondary effluent at the Wervershoof WWTP. This data can provide insight to the relative conditions of the wastewater the following day when the sample was taken. Additionally, there was no precipitation from March 13th _{to March 15}th_{, 2017 to affect the results of the sampling. The primary concern}

with the presence of precipitation is the dilution of micropollutants and increase of pollutants found in runoff, resulting in a sample not representative of normal dry weather conditions of the wastewater effluent. The lack of precipitation during the sampling period also strengthens the argument that the March 13th _{sample is representative of the}

24hr sample taken the day after, due to the similarity of conditions of the wastewater effluent. Analysis of the March 13th _{effluent yielded parameters within a standard}

deviation of the 6-month averages, and results that show strong correlation with average water quality data from the month of March. Measurements of TKN, NH4, NO2, NO3,

NOx, total nitrogen, and PO4 all yielded concentrations within a single standard deviation

of the 6-month average and average data from March. Limited data from the date of the 24 hours sample reduces the number of comparisons that can be made with the overall effluent wastewater characteristics of the Wervershoof WWTP. However, due to the lack of variability in water quality parameters from the sample in comparison to the 6-month average water quality data, the dry conditions during sampling, the 24 hour sample used in the research is determined to be representative of the typical Wervershoof WWTP effluent.