Ecological Mobile Solution for Reactivating the Sludge from the

Natural Reservation Techirghiol Lake

Victorita Radulescu

Department of Hydraulics, Hydraulic machinery and Environmental Engineering,

University Politehnica of Bucharest, Splaiul Independentei 313, Bucharest, Romania

Keywords: Ecosystems, Environmental engineering, Environmental friendly manufacturing techniques, Marine pollution,

Systems biology

Abstract: In Romania there are two nature reserves with salt water, Mangalia and Techirghiol Lakes. They are currently

facing new environmental issues. Their therapeutic mud, well known since the 19th century, has recently been

affected by new deep-water streams. They occurred as a result of numerous local earthquakes of low intensity.

The composition of water and saprophytic sludge changes due to their flow rate. Under these conditions, new

species of freshwater-specific vegetation have developed, which has led to a complex process of

eutrophication of the lakes. This produces a much faster vegetable sludge that disturbs the balance of the old

active, saprophytic one. Experimental measurements performed during 2015-2018 illustrate the current

environmental conditions, associated with the living conditions of birds and animals existing here, many of

them protected by law. For the rehabilitation of the Techirghiol Lake, a prototype was implemented, currently

being patented in Romania, and placed on a mobile pontoon powered by photovoltaic panels. He is able to

collect and partially dry this newly developed mud. It is described its scheme as well as the main steps during

an operating cycle. This model is suitable for nature reserves because it does not disturb the environment. The

extracted sludge is additionally dried in specially arranged places to be used in agriculture as an organic

fertilizer, to restore the quality of nearby agricultural land.

1 INTRODUCTION

In recent decades, the Black Sea area has faced

unexpected problems caused by natural causes or by

human interference. An increase in the number of

small earthquakes recorded in deep waters has led to

the appearance of freshwater streams, with low flow

rate, but over time with significant consequences on

the composition of the seawater in the area. These

currents produce local erosion, followed by changes

in the appearance of the coast).

The earthquakes were recorded mainly in the

southern part of the coast, near the localities of

Mangalia, 2 Mai, Techirghiol and Vama Veche.

Techirghiol Lake is well known since the 19th

century due to its therapeutic mud (Fioravanti and all,

2014).

Sand erosion and freshwater penetration affect the

aquatic environment, causing changes in the

characteristics of the activated sludge. The

https://orcid.org/0000-0002-8707-1914

saprophytic mud with therapeutic effects rich in

minerals has a very dense and oily appearance, being

extracted from depth and used successfully in the

treatment of rheumatism, anemia, rickets,

spondylosis, hypothyroidism, neuromotor problems,

skin, or endocrine disorders.

Fresh water enters especially the eastern part of

Lake Techirgiol (Environmental Romanian Strategy,

2013-2030). In that area, the vegetation specific to

fresh water but also resistant to semi-salt water

appeared and developed excessively in the whole lake

(Selman, 2007).

Salt water does not allow the sun to penetrate

easily (Schinler, 2012). In this case, this excess

vegetation rots quickly, turning into mud and

overlaps the therapeutic one. Here, even in cold

winters, the water never freezes, so this new rotten

vegetation quickly produced the eutrophication of the

lake. The local biological and chemical balance is

Radulescu, V.

Ecological Mobile Solution for Reactivating the Sludge from the Natural Reservation Techirghiol Lake.

DOI: 10.5220/0011105300003355

In Proceedings of the 1st International Joint Conference on Energy and Environmental Engineering (CoEEE 2021), pages 46-50

ISBN: 978-989-758-599-9

affected due to the rapid and large-scale production

of this type of sludge (Pullin and Andrew, 2012).

Therapeutic mud is formed as a result of bacterial

decomposition of aquatic organisms such as seaweed

and crustaceans Artemia salina, after the end of their

natural life cycle (Mathew and all, 2020). This sludge

is produced over a long period of time. Eutrophication

sludge overlaps the active one, minimizing its

concentration and therapeutic effects.

Since 2006 both lakes are registered as Nature

Reserves, Ramsar Sites - Protected Areas, due to the

specific vegetation and especially due to the birds that

winter here or that pass and rest during the migration.

More than 20,000 birds are recorded in Techirghiol

Lake, some of them endangered species, now under

the protection of the law (OUG, 2007).

The main objective of this research is to

rehabilitate this ecosystem, without using classical

solutions based on conventional fuel that produce

noise and odor and that affect biological and aquatic

life. Classical aggregates disrupt the nesting

conditions, the proper reproduction of birds and

animals, the rearing of chickens and their efficient

feeding, both of certain local and migratory birds.

Previously tested methods have not been shown to be

effective.

This prototype is autonomous, made on a mobile

pontoon powered by photovoltaic (PV) panels

(Radulescu, 2019). Both lakes are located in an area

with high solar radiation. The eutrophication sludge

placed above the therapeutic one is relatively easy to

collect. After collection, it is compacted and partially

dried on the pontoon. This solution meets EU

directives for the promotion of renewable resources

in new technical solutions with environmental

benefits.

This method allows the restoring the balance of

active sludge and subsidiary an efficient, adequate

and fast consumption of the extracted vegetable

sludge, used as organic fertilizer in saline soils such

as those in the Dobrogea area. The composition of the

nutrient-rich sludge is perfectly organic to be used as

a natural fertilizer in "green agriculture".

2 HYDROLOGIC

CHARACTERISTICS

The problems in this area have required effective

measures to protect nature reserves since 1982. In the

last two decades, more than 80 earthquakes with an

intensity of 3.0-3.8 on the Richter scale have been

recorded. These, combined with excessive irrigation

of agricultural land, to reduce the concentrations of

nitrates accumulated during the communist period,

led to the emergence of underground freshwater

streams. They have led to a process of sweetening of

the saline aquatic ecosystem.

The results, obtained by experimental

measurements for Lake Techirghiol, are next

illustrated. In order to minimize the infiltrations,

dams were built in 1983 and 1989, mainly to protect

the Mangalia shipyard but also the natural ecosystem.

Currently, the lake water is divided into three areas,

almost as separate entities. The first with salt water

with 52-68 grams of salt per liter (g/l) located in the

area closest to the sea, a saline area with 16-18 g/l as

an intermediate area and an area with almost fresh

water with 1-2.8 g/l, located near the locality Eforie

Nord, Figure 1.

Figure 1: The Techirghiol Lake water structure with the

specific areas and the current location of the therapeutic

mud (black).

The active mud, sediment from Lake Techirghiol

belongs to the group characterized as therapeutic

estuary sludge. It is the product of complex long-term

biological and chemical processes. The conformation

of the lake basin, the available water currents and the

phytoplankton determine the non-uniformity of the

sludge area. The thickness range varies from a few

centimeters to 2-3 m, structured in three layers.

Changes in the chemical composition of the lake

water minimize the sludge reserves, which have

decreased significantly in recent years. The physical-

chemical composition of the sludge is a mixture of

three phases:

- Solid phase, consisting of mineral and organic

particles, of different sizes;

- Colloidal fraction composed of a mineral and

organic substance such as mud;

- Liquid phase, consisting of an aqueous solution

of soluble substances.

This solution softens and fills the gaps between

the particles and the colloidal solid components of the

sludge. To these components are added some

microorganisms present in the sludge and decaying

plant debris. Figure 1 shows the effective division

into two parts of the mud from Techirghoil Lake,

noted: A- therapeutic mud (black color) and B-

Ecological Mobile Solution for Reactivating the Sludge from the Natural Reservation Techirghiol Lake

unusable sludge for human health. The general

chemical composition of the sludge is:

- 69-71% humidity, based on natural sludge;

- Volatile substance from 6.4 to 7.21%;

- The rest, about 22-23% mineral sequence.

This area is now full of swampy vegetation,

characteristic of fresh water. Due to heavy rains in

2005 and 2008, of about 230 l/m

recorded in 8 hours,

and of approximately 270 l/m

in 7 hours,

respectively, the water level in the freshwater area

received a surplus of about 2.3 million cubic meters

and about 2.5 million cubic meters, respectively,

which allowed a significant increase in water levels

throughout the lake by about 110-120 cm.

Additional fresh water was discharged into the

intermediate brackish zone and from there shortly

into the salt water zone.

As a result, since 2010, the specific freshwater and

swamp vegetation has developed massively in almost

all three areas of the lake, affecting local

environmental conditions. Figure 1 illustrates the

areas from which therapeutically active sludge can be

collected, represented in black. The dark gray area

represents areas with mixed saprophytic and vegetal

mud, and the rest is covered by vegetation.

Between 2015 and 2018, a team of researchers

consisting of chemists, biologists and engineers

performed measurements on the quality and

characteristics of water and mud, in all three areas,

20-25 cm above the bottom of the lake, in the

sedimentation bed. Some of the results obtained are

presented in Table 1, for aquatic and ecological data.

Table 1: Techirghiol Lake water characteristics.

Min Max Av SD

WL 4.02 4.21 3.24 0.11

SSD 0.43 1.17 0.83 0.29

TSM 12.7 49.8 29.1 14.1

TN 0.52 2.03 1.14 0.42

TDN 0.34 1.64 0.92 0.39

NH4+-N 0.055 0.51 0.242 0.137

TP 4.02 4.21 3.24 0.11

DTP 0.034 0.072 0.054 0.012

Chl-a 0.014 0.032 0.023 0.01

VPF 2.58 16.3 7.02 3.78

Where the notations are: Min - Minimum value,

Max - Maximum value, Av - Average value, SD -

Standard Deviation, WL- Water Level, SDD-

Sediment Scattered Dosing, TSM -Total Suspended

Matter, TN - Total Nitrogen, DTN-Dissolved total

nitrogen, Ammonium-Nitrogen NH4+-N, TP - Total

Phosphorus, DTP - Total Dissolved Phosphorus, Chl

- Chlorophyll, and VPF- frequency of the pixel i in a

set of n points, from the selected measurements.

Techirghiol Lake is the largest salt lake in

Romania, with a length of 7,500 m, a maximum depth

of 9 meters and a salinity of water with an average of

85-90 g/l. The qualities of mineralized salt water and

saprophytic mud, used in the treatment of various

diseases, make this place well known throughout the

world. A sanatorium for treatment was opened in

Techirghiol in 1899. In 1924, at the World's Fair in

Paris, the sludge from Lake Techirghiol received the

gold medal, thus recognizing its therapeutic effects.

Table 2 shows how the effective mineralization

has evolved in the last 70-90 years. There is a

permanent decrease in water salinity and recorded

higher concentrations of magnesium, calcium and

sulphate ions.

Table 2: Techirghiol Lake water characteristics.

Yea

1936 1996 2014 2018

Salinit

y(g

)

99.6 81.485 65.1 < 60

In the last two decades, Lake Techirghiol has

undergone the most important changes in the

composition of the water and, implicitly, in the

characteristics of the mud. Table 3 illustrates some

average values of the measurements, for water

composition over the last decade.

Table 3: Water composition.

Indicato

2014 2016 2018

1 Fixed residue 55844.22 62447.42 66780.12

2 CBO

7.87 8.16 9.05

3 CCOMn 34.57 39.17 41.01

dissolve

8.61 7.84 6.86

5Ca

202.24 221.82 240.4

2369.32 2571.34 2777.4

3 ENVIRONMENTAL AND

BIOLOGICAL CONDITIONS

The invertebrate fauna that inhabits the lake is

dominated by the saline crustacean Artemia, which

together with the crystalline alga Cladophora

provides the raw material for the production of

saprophytic sludge. Its active mineral components

give it a special therapeutic value.

In such diverse local conditions, the vegetation

resembles the marine one, being present halophilous

species such as Salicornia europaea, Artemisia

santonica, etc. Among the species mentioned, the

brown alga Cystoseira Barbata Sueda salsa the sea

CoEEE 2021 - International Joint Conference on Energy and Environmental Engineering

grass due to chemical changes of water are

endangered species, along with four other species of

invertebrates and five species of fish.

The vegetation has developed and adapted

continuously. Habitats and wetlands with coastal

features ensure good development conditions for a

wide variety of species.

The high salinity of the lake and the constant wind

that mixes the water (nearby is the Black Sea) make

the lake never freeze and be attractive to migratory or

wintering birds. Approximately 150 species of local

or transit birds are known, reaching over 20,000

specimens during migration. Among them are many

endangered protected species such as Copper Duck -

Oxyura leucocephala, red-necked goose - Branta

ruficollis (one of the rarest species of geese on the

planet), winter swan, white caliph -Tadorna tadorna,

curly pelican, black-headed gull-Larus

melanocephalus, pelican, etc.

In Figure 2 are illustrated some of the birds here

mentioned: red-breasted goose, Mediterranean gull,

curly pelican, white caliph, great crested grebe and

great flamingo.

Figure 2: Some protected birds from Lake Techirghiol.

According to recent data, Lake Techirghiol is

important for the wintering of many species of birds,

but also for the species that nest here. For all birds,

seaweed, sea crustaceans, sea fish, frogs or small

snakes are the main sources of food. The dense

growth of algae and other aquatic plants covering

over 25% of the surface interferes with the normal

biological ecosystem and certainly affects the life of

birds. Green plants produce oxygen in the sunlight,

but consume oxygen at night. Due to their excessive

development, the percentage of dissolved oxygen in

the water has decreased massively, and the fish have

become weaker or in some cases in hot summers have

died by suffocation.

Artemia Salina is the main filter in Techirghiol

Lake, which together with Cladophora have an

important role in increasing the phosphorus level. But

it is the mud that brought fame to this lake. It is the

chemical and biochemical product suffered by the

minerals and organic substances in the lake.

Lake Techirghiol has undergone significant

changes in water levels and, therefore, its salinity in

recent decades. Decreased salinity is harmful in this

case. Under these conditions, the therapeutic mud

recovers with difficulty. Therefore, it is necessary to

intervene to remove the sludge deposited much faster

and which significantly affects the quality of

saprophytic sludge.

4 THE IMPLEMENTED

SOLUTION

The solution next presented has been implemented

and tested since 2018 in Techirghiol Lake. In the

meantime, several improvements and automations

have been made to it to be better adapted to its

utilization in nature reserves. Figure 3 illustrates the

main components of the model, in a perfectly

ecological version. It is made on a mobile pontoon

equipped with a storage system, of 24 V/UPS inverter

with 60A 12-24V EP solar controller, plus mounting

and fixing accessories.

Figure 3: The main components of the prototype.

Next, the main steps are mentioned for an

operating cycle. The prototype advances by

propulsion, commanded by automation from the lake

shore (represents Step 1). The sludge is collected by

a screw pump (Step 2) provided with a suction pipe

with a diameter D = 55 mm, having a flow rate Q=25

l/min and power P = 0.75 kW. It is a stainless steel

pump recommended for sediment or sludge-laden

liquids as in this case (noted 2). The low flow rate

variant was selected so as not to disturb the deposited

sludge.

Ecological Mobile Solution for Reactivating the Sludge from the Natural Reservation Techirghiol Lake

Only the eutrophication sludge deposited over the

mineral sludge is extracted from the bottom of the

lake. The aspirated sludge is introduced into a

compaction system (noted 7) to remove excess water

(Step 3). Compaction is done by a screw system that

rotates in a conical portion of the suction pipe. The

sludge is then deposited in a fiberglass tank (noted 3)

with a capacity of approximately 0.6 m

(Step 5),

placed on the pontoon under PV-s.

The fiberglass tank has small holes in its upper

part to allow the release of a quantity of the extracted

and decanted water. It also ensures proper storage of

the extracted sludge. Mud is collected until the level

and weight sensors stop the pontoon from moving and

supplying it with sludge (Step 6).

From this point on, the sludge is partially dried

through a system of thin pipes through which hot

water flows, placed on the bottom of the fiberglass

tank (note 7). When the weight of the sludge is about

60-70% of its initial value, it is considered partially

dry, (Step 7) and it is discharged (Step 8). This sludge

partially s dried sludge is stored in special places until

final drying is ensured. After emptying the fiberglass

tank, a new cycle can begin. The control system of the

pontoon motion, automation that stops the pontoon

when the fiberglass tank is sufficiently filled with

mud, automation system that coordinates the entire

cycle and finally the system of power supply from

photovoltaic panels or storage of energy in batteries

when the model do not function are designed

separately.

5 CONCLUSIONS

The prototype can be moved on request in different

areas of the lake, the rest remaining completely

unaffected. Being a quiet system, it does not disturb

the life of the birds. Functioning without using classic

fuel and therefore without producing an unpleasant

odor, the installation can be used in nature reserves.

Being mobile, it can move in areas where there are no

bird nests, thus maintaining the biological ecosystem.

The extracted sludge is a natural fertilizer, full of

nutrients. It can be used on agricultural lands to

restore their optimal properties and characteristics, in

order to improve the obtained quantities of

agricultural crops.

By additional drying of the sludge, the time until

its utilization is shortened.

Thus, this solution has a double benefit. First of

all, the sludge produced by eutrophication is

extracted, restoring the chemical balance of the

therapeutic sludge in the places where the prototype

is implemented. Secondly, an efficient consumption

of the extracted sludge is ensured, as a fertilizer in the

salty soils of Dobrogea.

In the last years of implementation, by collecting

the eutrophication sludge, the surface from which the

therapeutic sludge could be collected increased by

about 8%.

The solution implemented in 2018 does not affect

the life, reproduction and nesting of birds. Many birds

were spotted near the pontoon, eating and resting in

the sun.

ACKNOWLEDGEMENTS

Thanks to the National Company "Romanian Waters"

which highlighted the problems from these Nature

Reserves. They also supported the team during the

measurements regarding the quality of the water and

the sedimentary material, during 4 years. They

partially financed the realization of the prototype and

allowed its implementation in the Techirghiol Lake,

which is under their management.

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CoEEE 2021 - International Joint Conference on Energy and Environmental Engineering