VU THI NGUYET
RESEARCH ON THE
APPLICATION OF AQUATIC PLANTS
IN THE TREATMENT OF SWINE WASTEWATER
Major: Environmental technology
Code : 62 52 03 20
SUMMARY OF DOCTORAL THESIS OF
ENVIRONMENTAL TECHNIQUE
Ha Noi - 2018
MINISTRY OF EDUCATION
AND TRAINING
VIETNAM ACADEMY OF SCIENCE
AND TECHNOLOGY
GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY
---------------------------
The work was completed at the Academy of Science and
Technology, Vietnam Academy of Science and Technology
Supervisors:
1. Dr. Trần Văn Tựa – Environmental technology academy
2. Prof. Dr. Đặng Đình Kim - Environmental technology
academy
Counter-argument 1:
Counter-argument 2:
Counter-argument 3:
The dissertation will be defended at the Academic Review
Board of the Institute, meeting at the Academy of Science and
Technology - Vietnam Academy of Science and Technology at
... on …’,
The dissertation can be reached at:
- Library of the Academy of Science and Technology
- Vietnam national library
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INTRODUCTION
1. The necessary of the project
In recent years, with the vigorous development of our nation, the
economy of rural area has also increased significantly; in which livestock
activities have contributed major income for many farmers. However, the
negative side of this quick development is environmental pollution caused
by the waste of livestock activities. It is estimated that only 40-50% of total
livestock waste is properly treated before discharging to environment, the
rest is directly released into ponds, lakes and canals.
To solve the environmental problem, several technologies have been
proposed and conducted to treat livestock waste like physical methods
which separate solid and liquid waste, or biological methods based on
anaerobic or aerobic condition. Among biological methods, biogas
technique has been proved to be an appropriate method to treat livestock
waste, and it has been widely used nowadays. However, some limitations of
biogas technique such as high P and N in outlet water that does not meet the
permitted standards lead to the necessary to construct an extra-treatment
step before discharging into the environment.
The extra-treatment step aims to reduce the remained P, N and
organic matters in effluent to meet standards before discharging. One of the
potential methods that are suitable for such a goal is eco-technology that
uses aquatic plants as a factor to treat the pollutants. This method has been
reported to have several advantages compared to regular wastewater
treatment system. Eco-technology is environmentally friendly, low cost,
easy to operate, and has a high and stable treatment efficiency. Many
countries in the world have studied to apply this method.
Vietnam is a promising country for applying Eco-tech to use aquatic
plants in water pollution treatment. However, the research and application
of this technology in Vietnam remains limited and/or unsystematic, only in
small experimental scale and lack of practical research to put the technology
into practice. Therefore, we conduct the study entitled: "Research on the
application of aquatic plants in the treatment of pig waste water" aiming
to propose an effective technology for livestock waste treatment, suitable
for Vietnam technological conditions, contributing to minimize
environmental pollution in residential areas. This is a promising strategy to
develop sustainable livestock farming along with environmental protection
and life quality improvement.
2. Study objectives
To propose Eco-tech model using aquatic plants to treat pig
wastewater after microbial treatment process in order to reduce
environmental pollution. The technology is feasible and practical.
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3. Research content
Content 1: Overview of the current status of pig wastewater pollution and
the treatment technologies; overview of Eco-tech using aquatic plants in
wastewater treatment in general, including waste water from pig farms.
Content 2: Evaluate the tolerance of some selected aquatic plants to COD,
NH4+, NO3-, pH, and their ability to treat COD, nitrogen, phosphorus in pig
wastewater after microbial treatment.
Content 3: Evaluate the efficiency of the treatment in different technological
types using aquatic plants with different wastewater loads.
Content 4: Establish and evaluate the treatment efficiency of the aquatic
plant system in reducing nitrogen (N), phosphorus (P) and organic matters
from pig farm wastewater after the microbial treatment.
4. Novel contributions of the study
- Selection of suitable aquatic plants for pig wastewater treatment
after microbial process based on the efficiency of COD, N, P removal.
- Selection of the suitable Eco-tech type using aquatic plants to treat
swine wastewater.
- Integration of the selected Eco-tech type into a treatment system of
30 m3 per day- night, effectively additional treating COD, N and P in
effluent from pig farms with low cost, simple operation, potential
enlargement and adaptation for farm conditions of Vietnam.
5. Thesis structure
The thesis is presented in 131 pages with 25 tables, 54 figures, and
166 references, including: 3-page introduction, 41-page literature review,
11-page experimental and research methods, 74-page result and discussion,
2-page conclusion and recommendation.
CONTENTS OF THE THESIS
Chapter 1: Literature overview
1.1 The situation of pig farm
Livestock farming is the development orientation of the stock-raising
sector. According to statistic number stated in 2016, there have been total
29 millions pigs in Vietnam, in which the Red River Delta reaches the
largest number with 7.4 million pigs (~26%), and this number has been
increasing over the years. This quick development, however, leads to many
problems to our environment caused by the increasing livestock waste.
1.2. Survey results of waste from pig farming and treatment technology
1.2.1. Environmental pollution caused by pig farming
A total of 20 pig farms were surveyed in five provinces: Hanoi, Vinh
Phuc, Hung Yen, Thai Binh and Hoa Binh. Water consumption in the farms
differs significantly from one to another, varying from 15 to 60
3
liters/pig/day.night, leading to the amount of waste water is a considerable
high number.
In terms of pollutant composition and level in pig wastewater before
biogas treatment; the COD, TN and TP in wastewater were very high
reaching to 3587 mg/l, 343 mg/l and 92 mg/l, respectively. After biogas
treatment, the parameters were reduced to 800 mg/l, 307 mg/l and 62 mg/l,
respectively. The amount of dissolved oxygen in wastewater before and
after biogas treatment was almost zero. Coliform index was multiple times
higher than the permitted standards. Therefore, the pollution caused by
piggery farm waste is an urgent situation and needs to be solved.
1.2.2. Current status of wastewater treatment technology
There are four typical types of technology applied by farms to treat
animal wastewater.
1 - The wastewater is treated with anaerobic ponds and then through
facultative ponds and then discharged into the environment (8.3%).
2 - Livestock wastewater is treated through biogas digester and then
discharged into canals (50%).
3 - Livestock wastewater is treated with biogas, followed by biological
ponds (25%).
4 - Livestock wastewater is treated by anaerobic stabilization, then treated
by anaerobic biological filter or aerotanks, finally through aquatic plant
ponds and then discharged (8.3%).
The remaining 8.3% of the farms do not apply any treatments but directly
discharge into the canals, causing serious pollution to the surrounding
environment.
1.3. Ecological technology in livestock wastewater treatment
- Types of aquatic plants in wetlands can be divided into three main
groups: semi-submerged aquatic plants, floating aquatic plants and
submerged aquatic plants.
- Types of technology used in Eco-tech for wastewater treatment:
surface flow technology, submerged flow technology, and floating aquatic
plant system.
- Pollutant removing mechanism: Nitrogen is removed by 3
mechanisms, nitrification/denitrification, ammonia evaporation and
absorption. Regarding P, the removal includes: absorption, via bacterial
metabolism, adsorption, precipitation and deposition with Ca, Mg ions...
The treatment process starts with microbial activities to form biofilms on
the surface of the aquatic plant shoots and roots; then the microbes digest
organic matters in water, releasing nutrient elements like N and P for plant
utilization.