Abstract

Water treatment plants are designed to continuously produce drinkable water, meeting defined criteria of potability. However, besides potable water, these plants produce sludges that are disposed of in the environment. The present work aimed to evaluate the sludges generated in two water treatment plants and disposed of in the margin of the Juturnaíba dam. Since alum has been used as a flocculating agent in these two plants, the concentrations of aluminum were measured in the sludges and in surface sediments. The generated piles are extremely soft to walk on and difficult to measure, so indirect modeling procedures had to be applied. The calculated mass of the sludge piles at each plant are similar and respectively 60,370 and 61,479 tons. The aluminum content of the residues, calculated according to its dosage, was 33.2 and 32.6 g kg−1 in the piles from the two plants. The amount of alum dosed to the water corresponds almost to the excess of aluminum in the sludge, compared to the sediments. It was concluded that regardless of the fact that residues are disposed of in very restricted areas, they are directly in contact with the water and may constitute a threat for the environment and humans’ health.

INTRODUCTION

Water is a natural resource that is essential for the maintenance of life and paradoxically it is often the final destination for wastes generated by practically all human activities. The byproducts generated by water treatment plants (WTPs), are examples of solid sludges improperly disposed of into water courses in Brazil (Tocaia dos Reis et al. 2007), and in other countries of the world (Kaggwa et al. 2001; Muisa et al. 2011; Tabe et al. 2016). The WTPs are responsible for producing treated water that attain quality standards established by national and international agencies for water potability (Botero et al. 2009) and their operations aim to remove suspended matter, natural organic matter and pathogenic organisms (Brant et al. 2011; Farenhorst et al. 2017). In Brazil there are about 7,500 WTPs providing coagulation, flocculation, sedimentation, decantation and filtration (Botero et al. 2009; Achon et al. 2013). Considering the large number of WTPs in Brazil, and the quality of the available raw water, studies of the final disposal of WTP sludges and their impact in the environment become relevant.

During the process of water coagulation, chemical agents are added to destabilize the suspended matter and colloids in the raw water, producing flocs that settle in decantation tanks (Katayama et al. 2015). Aluminum and iron salts are the most used coagulating agents in WTPs, predominantly aluminum sulfate – Al2(SO3)414H2O – also known as alum (Skeriotis et al. 2016). The generated and accumulated sludge in the decantation tanks and in the filters is recognized by the Brazilian Agency of Technical Standards (ABNT 2004) as an inert solid residue and therefore it cannot be directly disposed of in natural waters. However, the quantity and quality of these sludges depend on various factors such as raw water quality, treatment technology, type and dosage of coagulant, and characteristics and dosage of the auxiliary reagents used for coagulation (Hoppen et al. 2006; Hu et al. 2013; Oliveira et al. 2014). The alum sludge is classified, according to Ritcher (2009), as a gelatinous, non-Newtonian fluid, composed of aluminum hydroxide, and organic and inorganic particles, including bacteria and other organisms removed during coagulation.

The indiscriminate disposal of these sludges in the aquatic environment may increase the concentration of toxic metals, which could affect biota and can significantly decrease the transparency of the water, with the consequent reduction of the phytoplankton productivity (Chen et al. 2015; Yuan et al. 2016). Thus, under Brazilian laws, the disposal of WTP sludges is considered an environmental felony with direct effects in the aquatic environment (Sotero-Santos et al. 2005; Achon et al. 2013). Many solutions have been studied for the final disposal of WTP sludges, among them: (1) landfill disposal (Hidalgo et al. 2017), (2) application as sorption materials for the removal of dissolved contaminants (Choi & Yun 2006; Jung et al. 2016), (3) soil application (Januário & Ferreira Filho 2007; Bittencourt et al. 2012), (4) direct use in construction (Frias et al. 2014) and (5) in the production of ceramic material (Xie et al. 2012). However, most of the WTP sludges produced in Brazil are still inappropriately disposed of in the aquatic environment (Reis et al. 2007; Achon et al. 2013). For example, in the state of Minas Gerais, 87% of the sludges produced by WTPs of 175 counties, are directly disposed of in water courses without treatment (MP-MG 2009).

Aluminum is found in WTP sludges (Okuda et al. 2014), because, besides being an abundant constituent of rocks and soils of tropical environments (Cristancho et al. 2014), alum is the most commonly used coagulating agent. Aluminum constitutes circa 8% of rocks, and it is the most abundant metal of the Earth's crust. However, this element is a minor constituent in natural waters (Reimann & De Caritat 1998). Aluminum hydroxide in WTP sludges is only significantly soluble in acid or alkaline conditions, with pH values below 4, or above 9, rarely observed in natural environments (Bi & Yin 1995). Also, the solubility of Al is affected by the presence of inorganic complexing agents (F, H4SiO4, SO4−2) and organic compounds (Driscoll & Postek 1995).

Studies have shown that untreated alum sludges can compromise water quality and cause chronic effects in the biota (Kaggwa et al. 2001; Sotero-Santos et al. 2005; Muisa et al. 2011). Besides the toxicity to aquatic organisms, aluminum is recognized as a neurotoxic agent, and various statistical studies link this metal to the development or acceleration of Alzheimer's disease (Exley & Korchazhkinna 2001; Gonçalves & Silva 2007; Rondeau et al. 2009; Yang et al. 2017) although the exact mechanism of Al toxicity is not yet known (Maya et al. 2016).

For more than 50 years, the water from the Juturnaíba dam has been conventionally treated by two treatment plants. Presently under the concession of two private companies herein referred to as WTP1 and WTP 2, these WTPs are responsible for the supply of eight municipalities in Região dos Lagos (Rio de Janeiro). Between the years of 1960 and 2009, all the sludges generated in the WTPs were discarded without any treatment or drying on the dam banks, and a mix of water and flocs had been disposed of and settled in two large sludge piles. These sludges (rich in aluminum) are in direct contact with the water and sediment in the dam and may constitute a risk for the environment, but principally they may compromise the sustainability of the production of potable water. Regardless of the problems involved, the quantification of the volume of sludges disposed of by the companies and the levels of contamination could be done only by rough estimates, normally associated with the produced water balance and estimates of the concentrations of suspended matter. In the present study, we propose a few calculations to estimate the size of the waste piles, as well as to quantify the anthropogenic contributions of aluminum and the total mass of the WTP sludges.

MATERIALS AND METHODS

Study area

Juturnaíba is an artificial lake of some 43 km² formed from the flooded area of the Juturnaíba dam which is located in the Rio de Janeiro state, between the municipalities of Silva Jardim and Araruama (Figure 1). The dam is the principal source of water supply for the São João river basin, and receives, as principal tributaries, the rivers São João, Capivari and Bacaxá (Barcellos et al. 2012). The construction and filling of the dam occurred between 1978 and 1984 as it submerged stretches of river channels and the old Juturnaíba Lake with 8 km² of area (Barros 2007).

Figure 1

Location of the study area in the Rio de Janeiro state, Brazil. Sediment sampling points are indicated with numbers. WTPs (black) and the disposal areas (dark gray) are also indicated in the figure.

Figure 1

Location of the study area in the Rio de Janeiro state, Brazil. Sediment sampling points are indicated with numbers. WTPs (black) and the disposal areas (dark gray) are also indicated in the figure.

Volume of sludges – digital terrain model

In order to determine the volume of the sludge piles of both WTPs, two digital terrain models were constructed. Considering that there is no register of the topography that existed before the filling of the areas, it was necessary to model the basin, starting from the following observations and assumptions. (1) An eco-sounder was used to evaluate the slopes of the margins of the whole lake, which were assumed to be similar to the slopes in the basin where the sludges were dumped. (2) From an extensive bathymetric survey of the lake, it was observed that the depths are relatively constant being only around 2 to 3 meters. The above-water areas are constituted of a round hilly morphology and the submerged areas correspond to flat sedimentary fill plains. 3) It was also assumed that the limits of both sludge disposal areas could be delineated with sufficient accuracy from high definition satellite images (from Google Earth®).

Considering the above-mentioned assumptions, the digital terrain model was constructed using the software Surfer® to simulate the basins where the sludges were deposited. The horizontal limits of both areas were digitized and then depths were assigned according to the assumptions. The digital terrain model was constructed applying kriging interpolation in a diagram form.

Another digital terrain model was constructed for each area considering the present situation (with the filling of sludges). The surface area was considered approximately flat, as observed in the field, and the waste spreading front, in the limit of the submerged portion, was measured by an eco-sounder survey. The digital terrain model was constructed with the same software using kriging interpolation. The subtraction of one surface from the other allowed the determination of the volume of sludges in each area of disposal.

Volume of sludges calculated by the quantity of produced water

The estimates of annually produced sludge were calculated based on 20 months of real measurement of the suspended matter in the raw water (Wasserman 2012), and in the flow of produced water, declared by the companies, utilizing Equation (1).  
formula
(1)
where:
  • W = produced annual sludges (mg);

  • Qp = annual flow of produced water (m³ s−1), as declared by the companies;

  • SST = suspended matter (mg m−3);

  • DAl = calculated amount of Al(OH)3 precipitated from the dose of hydrated alum (mg m−3), as declared by the companies.

The water volumes produced year by year oscillated from the beginning of the operation, in the early 1960s, but the registers of these oscillations are quite accurate, since they could be calculated based on the financial budget of the companies (number of liters of water sold). The data declared by the WTPs are shown by periods, in Table 1. Considering that calcium oxides will largely remain dissolved and potassium permanganate is negligible, we did not include these chemicals in Equation (1).

Table 1

Water produced and the amount of Al (tons) on the waste pile, calculated with the dose declared by the companies

Start/End of operation Flow of produced water (m3Amount of Al2(SO4)3.14H2O (t) (per period) Amount of CaO (t) (per period) Amount of KMnO4 (t) (per period) 
WTP 1 
 1960/1998 359,510,400 14.380 2.876 179.7 
 1998/2004 113,529,600 4.541 908.2 56.76 
 2004/2009 157,680,000 6.307 1.261 78.84 
 Total 630,720,000 25.229 5.046 315.6 
WTP 2 
 1978/1998 693,792,000 24.976 2.761 Not declared 
 1998/2004 189,216,000 6.812 753.1 Not declared 
 2004/2010 122,990,400 4.428 489.5 Not declared 
 Total 1.005,998,400 36.216 4.004 Not declared 
Start/End of operation Flow of produced water (m3Amount of Al2(SO4)3.14H2O (t) (per period) Amount of CaO (t) (per period) Amount of KMnO4 (t) (per period) 
WTP 1 
 1960/1998 359,510,400 14.380 2.876 179.7 
 1998/2004 113,529,600 4.541 908.2 56.76 
 2004/2009 157,680,000 6.307 1.261 78.84 
 Total 630,720,000 25.229 5.046 315.6 
WTP 2 
 1978/1998 693,792,000 24.976 2.761 Not declared 
 1998/2004 189,216,000 6.812 753.1 Not declared 
 2004/2010 122,990,400 4.428 489.5 Not declared 
 Total 1.005,998,400 36.216 4.004 Not declared 
This accounting of the water produced by each WTP in each period allows estimation of the mass of produced sludge, in tons (Equation (2)). Real measurements of sludge density, allowed estimation of the volume of sludges in each of the sludge piles. The wet density of the sludges was measured by weighing 1 cm3 of the samples collected for the analysis of aluminum.  
formula
(2)
where:
  • P = total amount of waste produced and accumulated in waste piles (tons).

  • Wn = quantity of different wastes produced in mg for each period (n).

Anthropogenic aluminum by comparing the concentrations in the sediments and in the sludges

With the objective of evaluating the anthropogenic contributions of aluminum to the system, 24 samples of superficial sediments were collected with a Van-Veen grab, in the neighborhood of both water treatment plants (WTP 1 and WTP 2) and in the waste disposal areas. The sediments were stored in plastic pots, previously decontaminated, and kept refrigerated. In the laboratory, the samples were homogenized, freeze-dried, ground (with an agate mortar and pestle) and stored until analysis. The pseudo-total concentrations of aluminum present in the sediments were determined by acid extraction (inverted aqua-regia), based on the EPA method 3051A with the support of a microwave furnace (US-EPA 2007). The quantification of the metal concentration was carried out with inductively coupled plasma with optical emission spectrometry (ICP-OES). The analyses were done in EMPRAPA-Solos (Rio de Janeiro, Brazil), and followed standard procedures of analytical quality control, including: using analytical grade reagents (P.A.) obtained from Merck (Darmstadt, Germany), analysis of duplicated samples and simultaneous analyses of certificated material by SRM 2709A (San Joaquin Soil).

It was assumed that the sludge piles consist of: (1) suspended matter present in water; (2) alum added to promote flocculation (precipitating as anthropogenic Al(OH)3 or polymeric species of Al (Beecroft et al. 1995)); and (3) other reagents added in the process. It is a reasonable assumption that the composition of the sediments in the neighborhood of the piles reflects the concentrations of particulate matter (indeed, sediments are settled particulate matter) removed from the water during treatment. Therefore, it has been assumed that the particulate material that enters in the raw water has exactly the same composition as the sediments, apart from the added alum. The excess of aluminum identified in the sludges should therefore correspond to the mass of alum added in the flocculation process and decanted as aluminum hydroxide (as stated by the companies responsible for the plants).

RESULTS AND DISCUSSION

Dimension of the sludges piles

In the bathymetric study undertaken in Juturnaíba dam, carried out by Wada et al. (not published), the recesses along the shoreline were studied in detail to determine slopes. Examples of the measurements are shown in Figure 2. Significant slopes were observed in the margins of the dam. In Figure 2 it can be observed that only 5 meters away from the margin, depths of 2 and 3 meters were attained. With the exception of the area of the old Juturnaiba lake, which reaches depths of around 7 meters, the depths throughout the dam are relatively constant, with values between 2 and 3 meters. So, in the topographic model of the basin surface beneath the sludge piles a similar slope was assumed (0 m to 2 m depth slope at a distance of 5 meters from the margin) and in the inner parts of the pile, depths between 2 and 2.5 meters were assumed. The resulting assumed natural surface under each pile is shown in the diagrams presented in Figure 3. In the same Figure 3 the results of the modeled surface of the piles are also presented. With the aid of the volume measurement tool of Surfer the differences between both surfaces (empty and filled) were calculated, thus leading to an estimate of the volume of sludges in each pile. In the next section, these estimates of the volume of sludge in each pile are compared with the volume estimates calculated using the equation for sludge mass and the data in Table 1.

Figure 2

Examples of profiles measured from the other banks of Juturnaíba lake. 3.5 times vertical exaggeration.

Figure 2

Examples of profiles measured from the other banks of Juturnaíba lake. 3.5 times vertical exaggeration.

Figure 3

Block diagrams of the digital terrain model: (a) empty waste pile area for WTP 1; (b) filled waste pile for WTP 1; (c) empty waste pile area for WTP 2; (d) filled waste pile for WTP 2.

Figure 3

Block diagrams of the digital terrain model: (a) empty waste pile area for WTP 1; (b) filled waste pile for WTP 1; (c) empty waste pile area for WTP 2; (d) filled waste pile for WTP 2.

Calculation of the volume of sludges from the declared production and alum dose

Table 2 shows the estimated sludge masses generated by the WTPs and disposed of on the banks of Juturnaíba dam. The calculations are based on the data in Table 1, using Equation (2) and real measurements (annual average) of suspended matter in the dam water (54.6 mg L−1), obtained during monitoring of the water quality (Wasserman 2012). This table also shows the estimated volume of the waste in the piles calculated with the digital terrain model (described above) and the volume estimated assuming a density of 1,052 kg m−3 and 1,014 kg m−3 for WTP1 and WTP2, respectively, and the estimated concentration of added Al (g kg−1) calculated based on the declared dose of alum utilized by the companies. It can be seen that the estimate of mass of sludge, based on produced water [1] and based on the estimate of pile volume [3] are of a similar order of magnitude for WTP 1 (35.2%) and compare well for WTP 2 (0.3%).

Table 2

Estimated volumes and masses of sludges in piles located on the banks of the Juturnaíba dam, and the estimated concentration of anthropogenic Al (g kg−1) in the piles, calculated with the alum dose declared by the companies

Start/End of operation Discharge per period (t) [1] Estimated volume of sludge in the sludge pile (m3) [2] Estimated mass of sludge in the sludge pile (t) [3] Differences between estimations in tons (%) [4] Estimated anthropogenic Al concentrations in the sludge piles (g kg−1) [5] 
WTP 1 
 1960/1998 22,295     
 1998/2004 7,040     
 2004/2009 9,778     
 Total 39,114 57,495 60,370 21,256 (35.2) 33.2 
WTP 2 
 1978/1998 42,510     
 1998/2004 11,594     
 2004/2010 7,536     
 Total 61,640 59,688 61,479 161 (0.3) 32.6 
Start/End of operation Discharge per period (t) [1] Estimated volume of sludge in the sludge pile (m3) [2] Estimated mass of sludge in the sludge pile (t) [3] Differences between estimations in tons (%) [4] Estimated anthropogenic Al concentrations in the sludge piles (g kg−1) [5] 
WTP 1 
 1960/1998 22,295     
 1998/2004 7,040     
 2004/2009 9,778     
 Total 39,114 57,495 60,370 21,256 (35.2) 33.2 
WTP 2 
 1978/1998 42,510     
 1998/2004 11,594     
 2004/2010 7,536     
 Total 61,640 59,688 61,479 161 (0.3) 32.6 

[1] Calculation based on real measurement (average) of suspended particulate matter (54.6 mg L−1), during the study of Wasserman (2012) and determined using Equations (1) and (2).

[2] Size of the waste pile calculated with the topographic model, using Surfer software.

[3] Same method as [2], calculated in tons. Considering the density of sludge 1 equal to 1,052 kg m³ and sludge 2 equal to 1,014 kg m³.

[4] Differences between estimations made with the cartographic model and considering the mass calculations.

[5] Values calculated based on the dose of alum declared by the companies (Table 1) and in the estimated mass of the pile in [3].

Determination of Al contents in sediments

Table 3 shows the concentrations of aluminum in the superficial sediments (stations 1–14) and in the sludges (stations 15–24).

Table 3

Concentration (g kg−1) of pseudo-total aluminum measured on the superficial sediment and in collected samples of each sludge pile

  WTP 1
 
WTP 2
 
x̄ ± SD Min. Max. x̄ ± SD Min. Max. 
Al content (g kg−1) in the superficial sediment 28.2a ± 3.3 23.2 33.7 35.6b ± 4.3 28.1 41.0 
Al content (g kg−1) in the sludges 56.6c ± 4.2 50.4 60.8 62.0c ± 3.5 58.7 67.3 
Difference (g kg−1) (anthropogenic input) 28.4   26.4   
  WTP 1
 
WTP 2
 
x̄ ± SD Min. Max. x̄ ± SD Min. Max. 
Al content (g kg−1) in the superficial sediment 28.2a ± 3.3 23.2 33.7 35.6b ± 4.3 28.1 41.0 
Al content (g kg−1) in the sludges 56.6c ± 4.2 50.4 60.8 62.0c ± 3.5 58.7 67.3 
Difference (g kg−1) (anthropogenic input) 28.4   26.4   

a,b,cSame letters mean that average values are similar, according the Student's t test (p < 0.01).

The average values and the standard deviation of the aluminum content of the sediments close to WTP 1 were slightly lower than the sediments sampled close to WTP 2 (Table 3).

The results in Table 3 indicate that sludges disposed of on the banks of the Juturnaíba dam contained Al concentrations (g kg−1) approximately 50% greater than the superficial sediments sampled in the dam. This enrichment of aluminum in the WTP sludges could only be explained by the addition of alum during coagulation, and an estimate of the aluminum added can be obtained from the difference between the average concentrations of Al (g kg−1) stored in the sludge pile and in the sediments. From Table 2, the concentrations of Al stored in the sludge pile of WTP 1 as estimated from alum dosed was equal to 33.2 g kg−1 and in the waste pile of WTP 2 was 32.6 g kg−1. These values are similar to the excess aluminum concentration in each waste pile in Table 3, which were calculated as 28.4 mg kg−1 and 26.4 g kg−1 in WTP 1 and WTP 2, respectively.

CONCLUSIONS

Considering the fact that the sludges piles are very soft muddy areas, the execution of any kind of topographic measurement is impossible, so indirect procedures had to be developed. Two indirect procedures were applied in order to provide consistent measurements. The first calculation was based on the declared volume of produced water and the second was based on the construction of a topographic model, giving differences of 35.2% and 0.3% for sludges piles 1 and 2 respectively. These results show that the calculations based on the topographic model or based on the produced water give reasonable estimates of sludge volume and mass produced.

The estimated Al content in the WTP sludge piles was calculated considering the alum doses declared by the operating companies. The amount of Al added approximately matches the measured Al enrichment of the sludge compared to the natural sediments in the dam. This Al-enriched sludge in direct contact with water in the dam may constitute a threat for the health of ecosystems and humans. Further studies that evaluate the dispersion of these materials on the dam are important to elucidate the geochemical mobility of the metals present in the sludge.

ACKNOWLEDGEMENTS

This work was made possible with the support of the program Pensa-Rio (FAPERJ) through the grant #E-26/110-694/2012. JCW was granted a research fellowship #306714/2013-2. AMA was granted a doctorate scholarship from CNPq, and EYBW received a PIBIC-UFF scholarship. The authors are grateful to the reviewers for the comments and particularly to reviewer 2 for the relevant modifications suggested.

REFERENCES

REFERENCES
ABNT
2004
Resíduos sólidos (Solid residues). ABNT – Associação Brasileira de Normas Técnicas, Rio de Janeiro, Brazil
.
Barcellos
,
R. G.
,
Barros
,
S. R. D. S.
,
Wasserman
,
J. C.
,
Lima
,
G. B. A.
,
Chicayban
,
M. D.
2012
Availability of water resources from the São João River basin for a petrochemical complex of Rio de Janeiro, Brazil
. In:
Sustainable Water Management in the Tropics and Sub-Tropics and Case Studies in Brazil
,
1st edn
(
Bilibio
,
C.
,
Hensel
,
O.
&
Selbach
,
J.
, eds).
FUFPampa; Unikassel; PGCult; UFMA
,
Jaguarão, RS
,
Brazil
, pp.
653
683
.
Barros
,
S. R. S.
2007
A inserção da zona costeira nas territorialidades da bacia hidrográfica do rio São João - RJ: inter-relações, trocas e conflitos (The Insertion of the Coastal Zone in the Territorialities of the Hydrographic Basin of the São João River – RJ: Interelations Exchanges and Conflicts)
.
Doctorate in Geography
,
Department of Geography, University Federal Fluminense
,
Niterói, Brazil
.
Beecroft
,
J. R. D.
,
Koether
,
M. C.
&
Vanloon
,
G. W.
1995
The chemical nature of precipitates formed in solutions of partially neutralized aluminum sulfate
.
Water Research
29
(
6
),
1461
1464
.
Bittencourt
,
S.
,
Serrat
,
B. M.
,
Aisse
,
M. M.
,
Marin
,
L.
&
Simao
,
C. C.
2012
Application of sludges from water treatment plant and from sewage treatment plant in degraded soil
.
Engenharia Sanitária eAmbiental
17
(
3
),
315
324
.
Brant
,
J. A.
,
Koyuncu
,
I.
,
Lecoanet
,
H.
,
Veerapaneni
,
S.
&
Wiesner
,
M.
2011
Occurrence and composition of particulates in filter process streams
.
Journal American Water Works Association
103
(
12
),
46
60
.
Chen
,
Y. J.
,
Xiao
,
F.
,
Liu
,
Y. K.
,
Wang
,
D. S.
,
Yang
,
M.
,
Bai
,
H.
&
Zhang
,
J.
2015
Occurrence and control of manganese in a large scale water treatment plant
.
Frontiers of Environmental Science & Engineering
9
(
1
),
66
72
.
Cristancho
,
R. J. A.
,
Hanafi
,
M. M.
,
Omar
,
S. R. S.
&
Rafii
,
M. Y.
2014
Aluminum speciation of amended acid tropical soil and its effects on plant root growth
.
Journal of Plant Nutrition
37
(
6
),
811
827
.
Driscoll
,
C. T.
&
Postek
,
K. M.
1995
The Chemistry of Aluminum in Surface Waters
.
Lewis
,
California, USA
.
Exley
,
C.
&
Korchazhkinna
,
O. V.
2001
Promotion of formation of amyloid fibrils by aluminum adenosine triphosphate (Al-ATP)
.
Journal of Inorganic Biochemistry
101
,
215
224
.
Farenhorst
,
A.
,
Li
,
R.
,
Jahan
,
M.
,
Tun
,
H. M.
,
Mi
,
R. D.
,
Amarakoon
,
I.
,
Kumar
,
A.
&
Khafipour
,
E.
2017
Bacteria in drinking water sources of a First Nation reserve in Canada
.
Science of the Total Environment
575
,
813
819
.
Frias
,
M.
,
De La Villa
,
R. V.
,
De Soto
,
I.
,
Garcia
,
R.
&
Baloa
,
T. A.
2014
Influence of activated drinking-water treatment waste on binary cement-based composite behavior: characterization and properties
.
Composites Part B-Engineering
60
,
14
20
.
Gonçalves
,
P. P.
&
Silva
,
V. S.
2007
Does neurotransmission impairment accompany aluminum neurotoxicity?
Journal of Inorganic Biochemistry
1001
,
1291
1338
.
Hidalgo
,
A. M.
,
Murcia
,
M. D.
,
Gomez
,
M.
,
Gomez
,
E.
,
Garcia-Izquierdo
,
C.
&
Solano
,
C.
2017
Possible uses for sludge from drinking water treatment plants
.
Journal of Environmental Engineering
143
(
3
),
7
.
Hu
,
C. Y.
,
Lo
,
S. L.
,
Chang
,
C. L.
,
Chen
,
F. L.
,
Wu
,
Y. D.
&
Ma
,
J. L.
2013
Treatment of highly turbid water using chitosan and aluminum salts
.
Separation and Purification Technology
104
,
322
326
.
Jung
,
K. W.
,
Hwang
,
M. J.
,
Park
,
D. S.
&
Ahn
,
K. H.
2016
Comprehensive reuse of drinking water treatment residuals in coagulation and adsorption processes
.
Journal of Environmental Management
181
,
425
434
.
Kaggwa
,
R. C.
,
Mulalelo
,
I. C.
,
Denny
,
P.
&
Okurut
,
T. O.
2001
The impact of alum discharges on a natural tropical wetland in Uganda
.
Water Research
35
(
3
),
795
807
.
Katayama
,
V. T.
,
Montes
,
C. P.
,
Ferraz
,
T. H.
&
Morita
,
D. M.
2015
Quantification of complete cycle water treatment plant sludge production: a critical assessment
.
Engenharia Sanitária e Ambiental
20
(
4
),
559
569
.
Maya
,
S.
,
Prakash
,
T.
,
Madhu
,
K. D.
&
Goli
,
D.
2016
Multifaceted effects of aluminium in neurodegenerative diseases: a review
.
Biomedicine and Pharmacotherapy
83
,
746
754
.
MP-MG
2009
Informações técnicas referentes aos danos ambientais decorrentes do lançamento de lodo in natura, pelas Estações de Tratamento de Água, no ambiente – Parecer Técnico (Technical Information Concerning the Environmental Impacts from the Disposal of Untreated Sludges from Water Treatment Plants – Technical Advice)
,
Ministério Público do Estado de Minas Gerais
,
Belo Horizonte, MG, Brazil
.
Muisa
,
N.
,
Hoko
,
Z.
&
Chifamba
,
P.
2011
Impacts of alum residues from Morton Jaffray water works on water quality and fish, Harare, Zimbabwe
.
Physics and Chemistry of the Earth, Parts A/B/C
36
(
14–15
),
853
864
.
Okuda
,
T.
,
Nishijima
,
W.
,
Sugimoto
,
M.
,
Saka
,
N.
,
Nakai
,
S.
,
Tanabe
,
K.
,
Ito
,
J.
,
Takenaka
,
K.
&
Okada
,
M.
2014
Removal of coagulant aluminum from water treatment residuals by acid
.
Water Research
60
,
75
81
.
Oliveira
,
M. D.
,
Melo
,
L. D. V.
,
Queiroga
,
L. L.
,
Oliveira
,
S.
&
Libanio
,
M.
2014
Applying reliability analysis to evaluate water treatment plants
.
Water Science and Technology-Water Supply
14
(
4
),
634
642
.
Reimann
,
C.
&
De Caritat
,
P.
1998
Chemical Elements in the Environment: Factsheets for the Geochemist and Environmental Scientist
.
Springer-Verlag
,
Heidelberg
,
Germany
.
Reis
,
E. L. T.
,
Cotrim
,
M. E. B.
,
Rodrigues
,
C.
,
Pires
,
M. a. F.
,
Beltrame Filho
,
O.
,
Rocha
,
S. M.
&
Cutolo
,
S. A.
2007
Identificação da influência do descarte de lodo de estações de tratamento de água. (Appraisal of the influence of water treatment sludge disposal)
Química Nova
30
,
865
872
.
Ritcher
,
A. C.
2009
Àgua: métodos e tecnologia de tratamento (Water: Methods and Treatment Technology)
.
Blucher
,
São Paulo, Brazil
.
Rondeau
,
V.
,
Jacqmin-Gadda
,
H.
,
Commenges
,
D.
,
Helmer
,
C.
&
Dartigues
,
J. F.
2009
Aluminium and silica in drinking water and the risk of Alzheimer's disease or cognitive decline: findings from 15-year follow-up of the PAQUID cohort
.
American Journal of Epidemiology
169
(
4
),
489
496
.
Sotero-Santos
,
R. B.
,
Rocha
,
O.
&
Povinelli
,
J.
2005
Evaluation of water treatment sludges toxicity using the Daphnia bioassay
.
Water Research
39
(
16
),
3909
3917
.
Tocaia Dos Reis
,
E. L.
,
Barbosa Cotrim
,
M. E.
,
Rodrigues
,
C.
,
Faustino Pires
,
M. A.
,
Beltrame
,
O.
,
Rocha
,
S. M.
&
Cutolo
,
S. A.
2007
Identification of the influence of sludge discharges from water treatment plants
.
Química Nova
30
(
4
),
865
872
.
US-EPA
2007
Method 3051A. Microwave assisted acid digestion of sediments, sludges, soils and oils
.
SW-846, United States Environmental Protection Agency
,
Washington, DC
, p.
30
.
Wasserman
,
J. C.
2012
Programa de Monitoramento físico-químico, bacteriológico e de sedimentos no reservatório de Juturnaíba e em seus contribuintes (Rios Bacaxá, Capivari e São João) (Physico-Chemical, Bacteriological and Sediment Monitoring in the Juturnaíba Dam and its Tributaries)
,
UFF Network of Environment and Sustainable Development/Golden Lion Tamarin Association Ambiental P
,
Niterói
,
Brazil
.
Xie
,
M.
,
Shen
,
Q. W.
,
Liu
,
X. B.
,
Li
,
F.
&
Gao
,
D.
2012
Utilization of drinking-water treatment sludge in the manufacturing of ceramic tiles
.
Energy Education Science and Technology Part A-Energy Science and Research
29
(
1
),
267
276
.