According to the United Nations, the world population growth rate will be more pronounced in the coming decades, with an increase of 2.5–3 billion people by 2050, and with that, there will be an increase in the need for water, sanitation and hygiene (Leridon 2020). This phenomenon will boost vulnerability in socio-environmental, urban, economic and political spheres (Cutter et al. 2003). The United Nations Department of Public Information Report showed that in 2012, approximately 828 million people lived in slums with a growth rate of 6% per year (p.a.), and by 2020 it should reach 889 million in the urban migration process (UN 2012 and 2013). Coastal zones are more densely populated than inland areas and exhibit higher rates of population growth and urbanisation. The development of coastal areas has increased considerably in recent decades, producing socioeconomic changes and generating high pressure on ecosystems due to the exploitation of natural resources and pollution. Land use and urbanisation are also related to increasing population exposure and vulnerability along the coasts, especially in developing countries (Small, Nicholls 2003; Balk et al. 2009; Kron 2013; Neumann et al. 2015). In these zones, we can find vulnerable nuclei (VN), subnormal agglomerations, precarious settlements and slums, characterised by populations with low incomes and lack of access to safe drinking water, sanitation, and public housing and health policies, who live in non-conforming housing (NH) (IBGE 2010; SAO PAULO 2010; AGEM 2015; UN-BR 2018).
Port, industrial and tourist activities drive the Baixada Santista Metropolitan Region (BSMR) located in the Santos and São Vicente Estuarine Complex (SSEC) and induce invasions in flooded areas, where we find the largest slum on stilts in Brazil (Fabiano, Muniz 2010; Sampaio et al. 2011). The main actors behind this problem are the municipal governments who do not draw up adequate master plans for popular low-income occupations and parallel power organisations that rent out these irregular areas for the occupation of precarious housing. Housing changes and urban regularisation imply better sanitary conditions since the houses are now supplied by a regular water and sewage distribution system, in addition to allowing other essential services such as regular garbage collection. The improvement is a natural result of the replacement of irregular housing. The water quality of local watercourses automatically improves its indicators from the moment the raw sewage stops being deposited. Sewage discharge, inadequate waste disposal and port accidents compromise the quality of water and sediments. We analysed the population growth of VN in the SSEC and verified the water quality changes between 2005 and 2018.
The BSMR, with 1,848,654 inhabitants, is located on the south-eastern Brazilian coast, 2,428,737 km2, characterised by 65 km of continuous coastline. Bordered by the Serra do Mar cliffs, with remnants of the Atlantic Forest, there is a great diversity of ecosystems such as mangroves, estuaries, islands, sandbanks, coves, dunes, beaches and rocky shores. Most of these are protected through conservation units or other types of protected areas by law (IBGE 2018). The SSEC have several meandered channels that receive fluvial discharges that flow into Santos Bay through two channels (Fig. 1). On the eastern side, the Santos channel, with a width of 360 m and an average depth of 14 m, is maintained by dredging to navigate great ships. The São Vicente channel is on the west side, with an average depth of 8 m and a width of 585 m, narrowing to 185 m under the ‘Pensil’ bridge (Sampaio et al. 2011). Sewage, waste and emerging pollutants (salts and nutrients) harm public health in the estuary (CETESB 2017).
Location of the SSEC area. Red polygons limit areas of high vulnerability; cyan markers show localities of six water sample collection points (3 in Santos (ST1-3) and 3 in São Vicente (SV1-3)); orange lines represent artificial drainage canals; yellow markers define natural channels entry to the estuary in the municipalities of Santos (ST) and São Vicente (SV).
Source: Google Earth, adapted by the author, 2018.
SSEC – Santos and São Vicente Estuarine Complex.
We collect housing and population data from formal and informal areas. Each VN's coordinates and territorial space (Fig. 1) were also obtained and complemented by using Google Earth software (AGEM 2015; IBGE 2018; Annex A; Annex B). The study area group (SAG) brings together the number of households, populations and territories in formal and informal areas of Santos, São Vicente, Cubatão and Guarujá municipalities.
We calculate geometric annual growth rate (GAGR) by applying equation (Eq.) (1) (RIPSA 2018):
GAGR: geometric annual growth rate (% p.a.)
We calculated the GAGR for the number of non-compliant houses and the areas of occupancy of the VN (GAGRNH and GAGR m2) so that it was possible to identify four types of growth, as shown in Table 1. The type 1 cluster, with the increase in the number of houses and occupied areas, represents irregular and recurring occupations. Type 2, shows an increase in accommodation and a decrease in the area. The type 3 group indicates the preparation of a new irregular occupation. Type 4 represents the government's relocation actions but is not necessarily associated with the inspection and recovery of degraded areas.
Housing growth clusters (GAGRNH) and territorial (GAGRm2).
Type | Growth clusters | ||
---|---|---|---|
Dwellings (GAGRNH) | Territorial (GAGRm2) | Features | |
1 | + | + | Invasions and reinvasions |
2 | + | − | Verticalisation and densification |
3 | − | + | Demobilisation and pre-invasion |
4 | − | − | Demobilisation |
GAGR – geometric annual growth rate; GAGRNH – geometric rate of annual growth of the population in non-conforming housing.
Based on the data available in the National Sanitation Information System (NSIS), we calculate the sewage flow rate (Q) generated by human dwellings (HD) as 80% of water (Von Sperling 2014) according to Eq. (2), and the released pollutant load (PL) in the body of water according to equation (3):
Q: sewage flow per HD − m3 · year−1, PL: polluting load − m3 · year−1, IN051: loss ratio per house − m3 · house−1 · year−1, IN053: average water consumption per dwelling − m3 · dwelling−1 · year−1, NH: non-conforming housing − units · year−1, 0.8: contribution factor of sewage generation by housing, k: 54 g per inhabitant daily (value used in this study).
Sewage flow and polluting load (mainly phosphate) information was related to the estuarine water quality in six points (Fig. 1 and Table 2), obtained in 2011 and 2017 (CETESB). We compare results to the limits established in the Brazilian Law 357 CONAMA Resolution (BRAZIL 2005).
Identification of the channels of Santos and São Vicente and collection points in SSEC.
County | Coordinates (UTM) | Distance from mouth of Santos (km) | Distance from mouth of São Vicente (km) | |
---|---|---|---|---|
st1 | 369,107 E | 7,347,706 S | 3.1 | 31.9 |
st2 | 367,145 E | 7,350,411 S | 6.2 | 31.8 |
st3 | 366,363 E | 7,353,172 S | 9.0 | 26.0 |
sv3 | 355,832 E | 7,347,793 S | 21.4 | 13.6 |
sv2 | 355,575 E | 7,349,873 S | 27.3 | 7.7 |
sv1 | 358,418 E | 7,352,163 S | 29.7 | 5.3 |
Source: Google Earth, adapted by the author, 2018.
From 2005 to 2018, in urbanised areas, SAG municipalities presented a GAGR of 0.77% p.a., lower than the BSMR growth rate, which was 1.28% p.a. In the same period, 74 VN informal areas presented a geometric rate of annual growth of the population in non-conforming housing (GAGRNH) of 5.60% p.a., below the BSMR growth rate of 6.07% p.a. in 525 VN (Table 3).
Formal and non-conforming population (NH) between 2005 and 2018 in SAG municipalities.
Population (residents) | GAGR (% p.a.) | NH (AGEM) | NH (SABESP) | GAGRNH (% p.a.) | ||||
---|---|---|---|---|---|---|---|---|
2005 | 2014 | 2018 | 2005/2018 | 2005/2014 | 2005 | 2018 | 2005/2018 | |
Santos | 418,610 | 423,779 | 432,957 | 0.26 | 0.14 | 8,018 | 15,732 | 5.32 |
Cubatão | 113,271 | 123,785 | 129,760 | 1.05 | 0.99 | 8,620 | 2,935 | −7.95 |
São Vicente | 317,459 | 346,492 | 363,173 | 1.04 | 0.98 | 8,992 | 29,079 | 9.45 |
Guarujá | 276,945 | 303,397 | 318,107 | 1.07 | 1.02 | 19,300 | 39,345 | 5.63 |
SAG | 1,126,285 | 1,197,501 | 1,243,997 | 0.77 | 0.68 | 30,581 | 62,090 | 5.60 |
BSMR | 1,567,581 | 1,750,990 | 1,848,654 | 1.28 | 1.24 | 54,343 | 116,941 | 6.07 |
GAGR – geometric annual growth rate; GAGRNH – geometric rate of annual growth of the population in non-conforming housing; NH – non-conforming housing; p.a. – per year; SAG – study area group; BSMR- Baixada Santista Metropolitan Region.
Source: IBGE 2018.
VN growth clusters shown in Table 4 demonstrate a lower growth outlook for GAGRNH than that for RMBS. The positive double growth for dwellings and occupied areas (type 1) shows intense invasion dynamics, together with the densification and verticalisation process expressed in type 2 growth, which presented a GAGRNH of 7.25% p.a.; moreover, this presented a reduction of the occupied area of −1.94% p.a., representing 85% of the VN present in SSEC. The VN's demobilisation process, represented by cluster type 3 with a GAGRNH of −3.01% p.a. and GAGRm2 of 1.47% p.a., shows demobilisation and new areas in preparation for invasion. Cluster type 4, with a GAGRNH −4.54% p.a. and GAGRm2 −8.48% p.a., which, in addition to cluster type 3, represents 15% of the sampling plan, emphasises the disproportion between invasion and demobilisation/enforcement actions.
Housing and territorial growth clusters.
Type | NH | m2 | Qty VN | GAGRNH (% p.a.) | GAGRm2 (% p.a.) | |
---|---|---|---|---|---|---|
1 | + | + | 51 | 8.94 | 5.73 | |
2 | + | − | 12 | 7.25 | −1.94 | |
3 | − | + | 3 | −3.01 | 1.47 | |
4 | − | − | 8 | −4.54 | −8.48 | |
SAG | 74 | 5.60 | 0.09 | |||
BSMR | 599 | 6.07 | (*) |
BSMR – Baixada Santista Metropolitan Region; GAGR – geometric annual growth rate; GAGRNH – geometric rate of annual growth of the population in non-conforming housing; NH – non-conforming housing; p.a. – per year; SAG – study area group; VN – vulnerable nuclei.
Source: AGEM (2015); Annex A, adapted by the author, 2018.
not available.
Table 5 shows VN units that release sewage and influences water quality on monitoring points.
Number of VNs in growth clusters, housing and territorial growth rates correlated with collection points.
Cluster | st1 | st2 | st3 | sv3 | sv2 | sv1 |
---|---|---|---|---|---|---|
1 (+/+) | 14 | 2 | 8 | 16 | 3 | 8 |
2 (+/−) | 3 | 1 | 2 | 3 | 1 | 2 |
3 (−/+) | 2 | 1 | ||||
4 (−/−) | 3 | 3 | 1 | 1 | ||
NH (2005) | 9,170 | 1,986 | 3,471 | 6,888 | 3,308 | 5,758 |
NH (2018) | 15,172 | 4,846 | 5,012 | 20,633 | 3,659 | 12,768 |
GAGRNH | 3.95% p.a. | 7.10% p.a. | 2.87% p.a. | 8.81% p.a. | 0.78% p.a. | 6.32% p.a. |
New invasions | 4 | 0 | 4 | 11 | 2 | 5 |
GAGR – geometric annual growth rate; GAGRNH – geometric rate of annual growth of the population in non-conforming housing; NH – non-conforming housing; p.a. – per year.
Source: Annex A, adapted by the author, 2018.
Using the concept of SSEC average water renewal time, according to Leitão and Mateus (2008), the Santos Channel (with a width of 360 m and a depth of 14 m) and the São Vicente channel (with a width of 585 m and a depth of 8 m) are subject to a hydrodynamic regime of the seas in periods of 6 hours. According to Sampaio et al. (2011), the channels’ velocities vary between 0 m · s−1 and 0.5 m · s−1, and within SSEC currents, around 0.1 m · s−1 (Harari et al. 2007). In terms of water renewal flow under the influence of the tidal regime, the estimated range is 6 km and gives worse results at points sv3 and st3. The st3 point 9 km distant from the Santos channel is influenced by ship traffic in the Santos estuary channel, while the sv3 point does not receive large draft vessels. The average flow through the Santos channel is approximately 1,260 m3 · s−1, and the average flow through the São Vicente channel is 1,170 m3 · s−1. Table 6 presents the flow and polluting load of sewage discharged into water bodies in 2005 and 2018. The SAG received 451 tonnes · month−1 of pollutants in 2018, much higher than 137 tonnes · month−1 in 2011.
Sewage flow and PL released in SSEC in 2005 and 2018.
County | IN051 (m3 · month−1) | IN053 (m3 · month−1) | Total (m3 · month−1) | HD Number of irregular dwellings | Flow rate (m3 · month−1) | Polluting load (tonnes · month−1) | |||
---|---|---|---|---|---|---|---|---|---|
2005 | 2018 | 2005 | 2018 | 2005 | 2018 | ||||
Cubatão | 17 | 20 | 37 | 5,674 | 2,935 | 90,784 | 86,876 | 20 | 19 |
Guarujá | 22 | 21 | 43 | 12,818 | 22,887 | 215,342 | 787,313 | 47 | 170 |
Santos | 8 | 45 | 53 | 3,826 | 7,275 | 137,736 | 308,460 | 30 | 67 |
São Vicente | 19 | 19 | 38 | 8,263 | 29,042 | 125,598 | 882,877 | 27 | 191 |
SAG | 16 | 26 | 42 | 30,581 | 62,090 | 636,085 | 2,086,224 | 137 | 451 |
BSMR | 11 | 18 | 30 | 54,343 | 116,941 | 782,539 | 2,806,584 | 169 | 606 |
BSMR – Baixada Santista Metropolitan Region; PL – pollutant load; SAG – study area group.
Source: AGEM 2015; Sperling 2014; SNIS 2017; Annex B, adapted by the author, 2018.
Table 7 shows the non-conforming occurrences in water quality parameters recommended by Brazilian environmental legislation CONAMA 357 (BRAZIL 2005; CETESB 2011; Campuzano et al. 2013; CETESB 2017). During 2011, we verified 42 occurrences of non-compliance with quality standards, while in 2017 the number of occurrences rose to 56, with several new occurrences in the São Vicente channel, which receives increasing loads of sewage from the northwest of Santos-São Vicente Island.
Water quality measurements in non-conformity (“1” in yellow cells) with CONAMA 357.
Year | 2011 | 2011 | 2011 | 2011 | 2011 | 2011 | 2011 | 2011 | 2011 | 2011 | 2011 | 2011 | 2011 |
Station-Season | st1-S | st1-W | st2-S | st2-W | st3-S | st3-W | sv1-S | sv1-W | sv2-S | sv2-W | sv3-S | sv3-W | Total |
DO | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 | ||||
PTOTAL | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 | ||||
NH4 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 7 | |||||
TOC | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9 | |||
Ecotox. | 0 | ||||||||||||
Chlorophyll | 1 | 1 | |||||||||||
1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9 | ||||
Total 2011 | 3 | 3 | 4 | 3 | 5 | 3 | 1 | 3 | 3 | 4 | 6 | 4 | 42 |
Year | 2017 | 2017 | 2017 | 2017 | 2017 | 2017 | 2017 | 2017 | 2017 | 2017 | 2017 | 2017 | 2017 |
Station-Season | st1-S | st1-W | st2-S | st2-W | st3-S | st3-W | sv1-S | sv1-W | sv2-S | sv2-W | sv3-S | sv3-W | Total |
DO | 1 | 1 | 1 | 1 | 1 | 1 | 6 | ||||||
PTOTAL | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 12 |
NH4 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 7 | |||||
TOC | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 10 | ||
Ecotox. | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 12 |
Chlorophyll | 1 | 1 | 1 | 3 | |||||||||
1 | 1 | 1 | 1 | 1 | 1 | 6 | |||||||
Total 2017 | 5 | 3 | 5 | 3 | 6 | 3 | 6 | 4 | 6 | 3 | 7 | 5 | 56 |
DO – dissolved oxygen; NH4 – ammonia nitrogen; PTOTAL – total phosphorus; S – summer; TOC – total organic carbon; W – winter; Ecotox. (
Source: BRAZIL 2005; CETESB 2011; CETESB 2017.
The deterioration of the bathing water also increased between 2005 and 2017 (Table 8), with the discharge of domestic sewage being the main factor for the low water quality of the beaches of Santos, São Vicente and Guarujá (CETESB 2017).
Concentration of total coliforms in waterways urban effluent to beaches.
County | 2005 | 2017 |
---|---|---|
Cubatão (*) | 101 | 101 |
Guarujá (*) | to | 103 to 105 |
Santos (*) | 104 to 105 | 103 to 106 |
São Vicente (*) | 104 to 105 | 103 to 106 |
Bertioga | 103 | 103 to 104 |
Mongaguá | 103 to 104 | 103 |
Itanhaém | 103 to 104 | 103 |
Praia Grande | 104 to 105 | 103 to 106 |
Peruíbe | 102 to 103 | 103 to 104 |
Source: CETESB 2017, adapted by the author, 2018.
Municipality contemplated in SAG.
The evolution of GAGR from 2005 to 2014 in urbanised areas was 0.68% p.a. in SAG and less than 1.24% p.a. BSMR and other regions of the world, such as 1.52% p.a. in Latin America and the Caribbean (LAC), are at a rate of 4.57% p.a. in sub-Saharan Africa and at a rate of 4.53% p.a. in Western Asia (IBGE 2010; UN 2016; IBGE 2018). Paradoxically, in informal areas from 2005 to 2018, GAGRNH in SAG 74 VN was 5.60% p.a., while BSMR 525 VN reached 6.07% p.a., higher than all other areas in LAC (−0.75% p.a.), sub-Saharan Africa (3.12% p.a.) and Western Asia (3.89% p.a.) (Young, Fusco 2006; AGEM 2015; UN 2016; Annex A; Annex B). Except for Cubatão municipality, with a negative GAGRNH (−7.95% p.a.), the municipalities of SSEC presented VN with growth types 1 and 2, in non-conforming dwellings and the occupied area or areas of verticalisation and population concentration. Intense urbanisation has significantly altered the physical environment, and the conservation of natural areas near urbanised areas remains to be considered of little importance to the government. Young 2009; Moreira et al. 2017 emphasise that the lack of conservation of natural areas in BSMR contributes strongly to environmental degradation and the impacts related to urban activities. On the other hand, in Cubatão, housing policy is based on housing production through partnerships with the state and federal governments. Some projects only include new units, while others have joint urbanisation and housing production actions. In addition to the construction of about 10,000 houses, the projects foresee urban areas occupied by families. The Organic Law of the Municipality of Cubatão establishes in Article 7(2) the municipality's concurrent competence, together with the State of São Paulo and Brazil, to execute housing production programmes. Combining this provision with the relevant chapter on municipal housing policy (Arts. 207 to 211) is the foundation in the local legal system for such sectoral policy and competence that enables the municipality to conclude agreements with other federative entities (Gillan, Charles 2019).
There are significant social impacts of daily releases of
The relationship between economic growth and the release of contaminants has been known for some time. Garcia Occhipinti (1986) presented the most relevant aspects for analysing an ocean waste disposal system (OWDS), where he emphasised the tidal regime's interference in the gradient of contaminant concentrations. High concentrations of persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) are also associated with anthropogenic effects on SSEC (Fontanelle et al. 2019).
The sustainable development goal aims related to the environment, biodiversity and sustainable cities have encountered resource constraints and ineffective government actions (Shibata et al. 2015; WHO 2017; UN-HABITAT 2018). Insufficient urban land tenure regularisation in RMBS cities corroborates VN's ‘invisible’ growth and exerts negative impacts on transforming the urban environment and public health in SSEC waters and sediments. It is of great complexity to study a natural phenomenon that intensifies due to anthropic activities’ interference in coastal environments, especially those that cause eutrophication. The potentially harmful impact portrays this complexity, avoiding an alarmist attitude. We cannot avoid this phenomenon, but we must minimise its causes for maintaining tourism, fishing and improving public health.
Sixty-five percent of the area (Baixada Santista) is occupied by areas of permanent environmental preservation (APPs) with mangroves,
The geometric rate of annual growth of the population in non-conforming housing (GAGRNH) is approximately five times higher than that of the compliant population in the Baixada Santista Metropolitan Region (BSMR). It exceeds all world growth rates, even in the poorest regions of Latin America and sub-Saharan and West Africa.
The vulnerable nuclei (VN) growth clusters show that 85% of the VN result from invasions, reinvasions, densification and verticalisation, while 15% represent the government's areas’ demobilisation actions, without actions to recover degraded areas.
The release of sewage in the Santos and São Vicente Estuarine Complex (SSEC) by the study area group (SAG) exceeds 450 tonnes · month−1 and a flow of 2,650,000 m3 · month−1, and the negative impacts from the release and disposal of waste on the banks of water bodies pose risks to public health.
Estuary hydrodynamics do not promote the renewal of SSEC waters and turn its water into a large receptacle for sewage and emerging pollutants. As this is a port region, the contamination of these water bodies has potential risks of contamination and the spreading of diseases worldwide.
A comparison of these historical data clearly shows the escalation of nutrient entry into SSEC and increased concentrations associated with the growth of informal populations in the Santos metropolitan region beyond the limit of the estuarine system's carrying capacity, revealing the enormous pressure on the ecosystem.
The results show accelerated degradation of ecosystems, damage to public and environmental health, and potential risks of spreading disease in SSEC.
The re-urbanisation of the area using economic resources caused by the loss of water must be taken to reduce the risks of ecosystem degradation, damage to health and the spread of diseases.
This study has great potential to solve problems of urbanisation and sanitation in slum areas using resources from the economy generated by non-waste of treated water in irregular distribution. In a global scenario, this proposal could also be used in other regions of irregular housing in Brazil, and even studies of this nature in other parts of the world in less developed countries can lead to similar results and, consequently, solve water contamination problems.