**4. Methodology**

The first stage of the methodology employed was to conduct a survey of the bibliographical references, including those regarding the selection of the parameters adopted for this analysis. Several more specific data were investigated that are related to the local drainage basin and the sanitary sewage system, together with an analysis of the locality. The plants and records available of the drainage and sewage systems were investigated together with the respective basins concerned.

These were investigated together with the responsible bodies, including the municipal government of Rio de Janeiro and CEDAE (The State Water and Sewage Company) and the historical data obtained through the monitoring of the quality of the water carried out by the TECMA in the last few years.

There was also an analysis of the field measurement data and the specific collections of the samples taken from the surface water of the Lagoon. This took place twice a week during the period from January 1 to December 31, 2018, in the six sampling points that were strategically placed around the water body (LRF1 to LRF6). These data were made available by the TECMA, and a third party was responsible for analyzing the samples of water from the Lagoon.

Despite the wide array of parameters that were analyzed in the course of the monitoring plan, in the particular case of this study, the physicochemical parameters that were examined were as follows: temperature, salinity, pH, turbidity, dissolved oxygen, ammonia nitrogen, total phosphorus, and orthophosphate. The biological parameters included *Escherichia coli*. The selection of these parameters was based on their degree of importance in representing the hydric quality for required use and grounded on the bibliographical support provided by this study. It should be noted that the parameters for monitoring were the same as those employed by Mello [17].

The temperature, salinity, pH, turbidity, and concentration of dissolved oxygen were determined in situ by means of the portable field recording equipment with electrodes. The samples of water for the analysis of the other parameters were obtained with the aid of collecting bottles and packaged in polyethylene flasks of appropriate volumes. These were duly labeled and preserved and then packed in thermal boxes with ice and sent to the TECMA laboratory for analysis in a timescale that ensured the tests were carried out within the deadline for preserving validity.

**39**

[29–31].

*Environmental Monitoring of Water Quality as a Planning and Management Tool: A Case…*

It was found that the different groups of phytoplankton displayed variations in their levels of chlorophyll a; since not all the blooming of the algae affected the values of the parameter, they were not regarded as important for the purposes of this study. The benchmark determination methodology in situ, for the collection and preservation of the samples, as well as the analysis, was that recognized by the Standard *Methods for the Examination of Water and Wastewater*, APHA-AWWA-WEF, 22th

The results for each parameter were analyzed per season and formulated into line graphs that contain the maximum, minimum, and average values at each stage of the sampling. Calculations were also made of the average values for the surface of each parameter in the years 2014, 2015, and 2016, with a view to supplying comparative values for the seasonal averages of 2018 and thus assisting our understanding of the alterations that were observed. The spatial and temporal variations that were noted were discussed together with the other results. The data were also assessed by comparing them with meteorological data on rainfall, radiation, and air temperature, which was collected from the meteorological station installed in the Rowing Stadium of the Lagoon and also supplied by TECMA, with the aim of determining their influence on the results of the physicochemical and biological parameters.

Temperature is a factor of paramount importance for the aquatic ecosystem because it plays an essential role in the control of the environment by influencing physical, chemical, and biological processes including vital factors such as primary productivity and the decomposition of organic matter [25, 26]. The Central Institution of the Environmental System of São Paulo (CETESB) [27] stresses the importance of analyzing the temperature of the water, since aquatic organisms have differentiated limits of thermal tolerance and the best temperatures for growth. Thus as high solar radiation naturally results in an increase in the temperature of the water, the supply of water used in refrigeration systems results in a rise in the receptor body which can lead to a reduction in the concentration of dissolved oxygen and/or an acceleration of the metabolism of the phytoplankton which is favorable for the occurrence of blooming. Alterations in temperature can also sharpen the

In the period being analyzed, it was noted that there was a horizontal uniformity in terms of water temperature on the surface layer of the Rodrigo de Freitas Lagoon. The averages, with regard to the six sampling points, ranged from 24.1 to 30.0°C,

It was noted that together with other factors, the high temperatures of the water in the Lagoon in the spring of 2018 could have favored the phytoplanktonic blooming of the cyanobacteria *Synechocystis* spp., which occurred in the period December 10–17. It should be underlined that the fact that cyanobacteria have a preference for high temperatures has been demonstrated in a number of studies

When compared with the springs of 2014, 2015, and 2016, the parameter in 2018

with lower temperatures in winter and higher in summer (**Figure 5**).

was 1–1.5°C above the others as can be observed in **Table 6**.

*DOI: http://dx.doi.org/10.5772/intechopen.88687*

Edition, 2012.

**5. Results and discussion**

sensation of taste and smell in the water [28].

*5.1.1 Temperature and phytoplanktonic blooming*

**5.1 Temperature**

*Environmental Monitoring of Water Quality as a Planning and Management Tool: A Case… DOI: http://dx.doi.org/10.5772/intechopen.88687*

It was found that the different groups of phytoplankton displayed variations in their levels of chlorophyll a; since not all the blooming of the algae affected the values of the parameter, they were not regarded as important for the purposes of this study. The benchmark determination methodology in situ, for the collection and preservation of the samples, as well as the analysis, was that recognized by the Standard *Methods for the Examination of Water and Wastewater*, APHA-AWWA-WEF, 22th Edition, 2012.

The results for each parameter were analyzed per season and formulated into line graphs that contain the maximum, minimum, and average values at each stage of the sampling. Calculations were also made of the average values for the surface of each parameter in the years 2014, 2015, and 2016, with a view to supplying comparative values for the seasonal averages of 2018 and thus assisting our understanding of the alterations that were observed. The spatial and temporal variations that were noted were discussed together with the other results. The data were also assessed by comparing them with meteorological data on rainfall, radiation, and air temperature, which was collected from the meteorological station installed in the Rowing Stadium of the Lagoon and also supplied by TECMA, with the aim of determining their influence on the results of the physicochemical and biological parameters.
