Scholarly article on topic 'Developing an Integrated Sustainable Sanitation System for Urban Areas: Gaza Strip Case study'

Developing an Integrated Sustainable Sanitation System for Urban Areas: Gaza Strip Case study Academic research paper on "Agriculture, forestry, and fisheries"

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Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — Samir Afifi, Samir Alnahhal, Sadiq Abdelall

Abstract A vertical flow (reed bed) constructed wetland was used for treating bio-solid and gray water. The results present a positive performance in treating the bio-solids and well-stabilized accumulated organic material in the bed formed fertile soil. Moreover, using vertical flow reed bed of liquid waste treatment showed removal of around 70% of organic matter indicator Biological Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD). The Fecal Coliform (FC) removal was around 2 logs (99.9%) with a retention time of less than two days. The effluent can be used in agriculture or groundwater recharge. A semi-dry toilet followed by anaerobic/aerobic units is in planning to be coupled with an existing system. The system mainly depended on separating of the human excreta from the urine and gray water. The two separated fractions will be treated in vertical flow reed bed to produce organic fertilizer and reclaimed water for reuse. Such systems could be a suitable solution for wastewater problems in Gaza strip and similar regions. The designed and planned system integrated environmental and technical sound approaches with socio- economical aspects. In addition, the designed system implemented the idea of a natural and closed circle of water and nutrients “from food to food”.

Academic research paper on topic "Developing an Integrated Sustainable Sanitation System for Urban Areas: Gaza Strip Case study"

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Procedía CIRP 26 (2015) 767 - 774

12th Global Conference on Sustainable Manufacturing

Developing an Integrated Sustainable Sanitation System for Urban Areas:

Gaza Strip Case study

Samir Afifi1*, Samir Alnahhal2, Sadiq Abdelall3

Environment and Earth Science, Islamic University of Gaza, Palestine 2Palestinian Environmental Friends Association, Palestine 3Engineering Faculty, Islamic University of Gaza, Palestine Corresponding author. Tel.: +972599465665; fax: +97282131506 E-mail address: safifi@iugaza.edu.ps

Abstract

A vertical flow (reed bed) constructed wetland was used for treating bio-solid and gray water. The results present a positive performance in treating the bio-solids and well-stabilized accumulated organic material in the bed formed fertile soil. Moreover, using vertical flow reed bed of liquid waste treatment showed removal of around 70% of organic matter indicator Biological Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD). The Fecal Coliform (FC) removal was around 2 logs (99.9%) with a retention time of less than two days. The effluent can be used in agriculture or groundwater recharge. A semi-dry toilet followed by anaerobic/aerobic units is in planning to be coupled with an existing system. The system mainly depended on separating of the human excreta from the urine and gray water. The two separated fractions will be treated in vertical flow reed bed to produce organic fertilizer and reclaimed water for reuse. Such systems could be a suitable solution for wastewater problems in Gaza strip and similar regions. The designed and planned system integrated environmental and technical sound approaches with socio- economical aspects. In addition, the designed system implemented the idea of a natural and closed circle of water and nutrients "from food to food".

© 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of Assembly Technology and Factory Management/Technische Universität Berlin. Keywords: Gaza strip, sustainable sanitation, reed bed, semi-dry toilet

1. Introduction

Nowadays, it is estimated that there are 2.7 billion people without access to basic sanitation. Yet, worldwide, more than 90% of the wastewater does not receive any treatment at all, thus contaminate a large amount of fresh water [1]. As a consequence, it is estimated that every 20 seconds, a child dies globally due to diarrhoea, cholera and other enteric diseases as a result of poor sanitation [2].

In Gaza Strip, about 30 % of more than 1.7 million people have no access to sewage facilities which varies from areas. The total annual wastewater production is estimated to be 40 million m3 annually, of which 24 million m3 passes into sewerage networks [3]. Due to reduced capacity overloaded, and partially functioning of the existing wastewater treatment plants, this sewage is either untreated or partially treated, and finally released into the Mediterranean Sea [4].

The rest of daily produced wastewater (42%) is directly infiltrated to the ground without any further treatment through cesspools or pit latrines [5]. As a result of sewage infiltration and overexploitation, 95 % of the coastal aquifer, the sole source of fresh water available for Palestinians in the Gaza Strip, is polluted with dangerous levels of nitrates and chlorides way above the standards recommended by WHO [6].

In Gaza strip, the waterborne sanitation systems are conventional and have its drawbacks regarding the water use, cost, and the health risks. In this system about 50 to 100 liters of freshwater is consumed to evacuate daily production of 1 to 1.5 liters of excreta [5].

Gaza strip faces significant water crises, as about 180 million m3 is the annual overexploitation from the groundwater aquifer for deferent water uses. While only about 55 - 60 million m3 of total annual water needs is renewable

2212-8271 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of Assembly Technology and Factory Management/Technische Universität Berlin. doi:10.1016/j.procir.2014.07.158

and about 67 % is the annual deficit [5, 7]. The nitrate level in groundwater ranges from 100 - 150 mg/l due to the indirect injection of the wastewater into the soil through cesspools and the heavy use of chemical fertilizers in agricultural activities [8].

The way to sustainable management of natural resources is one of the greatest challenges of present time. The societies' sustainability depends essentially on secured water resources, food supply and an intelligent management of wastes. Sustainable sanitation aims to overcome the conventional sanitation systems drawbacks. It is not a certain technology, but an approach with certain underlying principles. There are a number of technologies that can be used to make sanitation and wastewater management more sustainable. Therefore, the main objective of any sustainable sanitation system is to protect and promote human health by providing a clean environment and breaking the cycle of disease. In order to be sustainable, a sanitation system has to be not only economically viable, socially acceptable, and technically and institutionally appropriate, it should also protect the environment and the natural resources [9].

The concept of sustainability is more of a direction rather than a stage to reach [10]. Nevertheless, it is crucial, that sanitation systems are evaluated carefully with regard to all dimensions of sustainability. Since there is no one-for-all sanitation solution, which fulfils the sustainability criteria in different circumstances to the same extent, this system evaluation will depend on the local framework and has to take into consideration existing environmental, technical, sociocultural and economic conditions. There is no "one-fits-all" approach; rather, the most adequate solution has to be found from case to case, considering climate and water availability, agricultural practices, socio-cultural preferences, affordability, safety, and technical prerequisites [10, 11]. Taking into consideration these entire range of sustainability criteria, Semi Dry Toilette System (SDTS) arises as a sustainable sanitation alternative to conventional sanitation systems, which can improve several social and ecological issues in rural and urban regions as well. The SDTS cope with essential minimal use of water to meet hygienic and socio-cultural needs and integrate reuse of emitted water and biosolid.

2. Scope of the work

The main scope of this work is to apply the SDTS approach under the local circumstances of Gaza strip and similar regions worldwide through source separation of the human excreta "bio-solid" and urine "liquid waste". The two separated fractions will be treated in vertical flow reed bed. Reeds act in many ways to alter the character of organic solids present in the wastewater [4]. Firstly, their root system provides oxygen, which boosts the population and activity of naturally occurring microorganisms, which accelerate the biodegradation of organic material. Secondly, the plants grow rapidly in this nutrient-rich medium and absorb some of the minerals. Thirdly, roots extend from the reed stems into the bio solids which create a system of channels in the bio solids, allowing for continuous drainage and preventing the formation

of a semi- impermeable layer, which is typical in unplanted beds [12].

The main concept of SDTS is to implement the idea of a close natural circulation system of water and nutrients "from food to food". The basic principle of the system is to collect excreta (Bio-Solid) separately from urine and gray water (liquid waste). The human excreta and bio kitchen waste will be treated using anaerobic digestion to produce Biogas (Energy) and stabilized fresh human excreta. The further treatment of bio-solid followed by vertical-flow reed bed (aerobic), which will generate an odor and pathogen free highly fertile soil. The separated urine and gray water will be treated in a second vertical flow reed bed and the treated water can be reused directly in agriculture or indirectly for groundwater recharge. The outcomes of the system ultimately ensures the production of new food and closing the loop of human nutrition as presented in Figure 1.

Figure 1: Integrated sustainable sanitation system for urban areas

Since many years, Gaza strip went through many sanitation systems in fragmented ways. Many researches and pilot projects were implemented to treat the bio-solid alone using different biological and environmental approaches. In addition, the liquid waste was also targeted in old and new researches.

Depending upon the current sanitation systems that mainly fulfill the requirements and steps of the SDTS, this work tried to incorporate up-to-date results with future planned development as shown in Figure 2. Such results and tests could help in integrating all current and needed systems with the advanced innovative technologies for reducing water consumption system and circulation for nutrients. Such integration will finally accomplish the concept of SDTS to make the source separation of the both bio solid and liquid waste and implement the full recycle of the waste elements: bio-solid, energy, liquid, and nutrients. The Gaza team implemented successfully the bio solid and gray water

treatments in vertical flow reed bed. The adopted innovative technology for the source separation and design of semi dry toilets are planned to be integrated with up to date results. Such toilets will design to separate the human excreta from the urine. The excreta will transformed through special ducts; or directly transformed to the anaerobic treatment units. The biosolid become more stabilized, the bad odor is reduced, and biogas is created to produce the energy. The reed bet treatment unit will be used to finally treat of bio-solid and to create the fertile black soil.

The separated urine" liquid waste" is collected and mixed with the other generated grey water from the different

domestic sources at the household level such as the shower, kitchen, washbasin, and laundry. The mixed grey water is finally transformed through the grey water network to the aerobic biological treatment unit (vertical flow reed bed), in which, the reclaimed water is transformed to the final outlet facility for reuse in agriculture or/and groundwater aquifer recharge. The following schematic diagram in Figure 2, summarizes the scope of the work and methodology.

In the following point, the so far achieved result of using vertical flow reed bed system for liquid and bio solid waste treatment will be presented.

Figure 2: Schematic diagram for the scope of the work and methodology

3. So Far achieved result

3.1. Bio-Solid waste treatment

such as sludge quality, climate, , loading rates, and feeding frequencies [14].

System design and operation

In Gaza Strip the human excreta are commonly accumulated in onsite sanitation systems such as septic tanks and cesspools where no sewage networks are available. The random discharge of this material resulting in degradation of environment and serious public health risks [4, 13] such as groundwater pollution and transmission of enteric related diseases [14]. Accumulated human excreta "septage" must be properly treated before disposal [4, 15]. However, the septage contains essential nutrients (nitrogen and phosphorus) and is potentially beneficial as fertilizers for plants. The organic carbon in the septage, once stabilized, is also desirable as a soil conditioner, because it provides improved soil structure for plant roots [15].

The Vertical flow constructed wetland was planted using reed bed for septage handle and disposal as low-cost and environmentally sound technique. In such system, both dewatering and organic matter decomposition by aerobic biological activity achieved and helped in final formation of organic material in fertile black soil. Several factors influenced vertical flow constructed wetland efficiency

The main dimensions of the septage vertical flow reed bed for treating the septage was; 3m length * 1.5m width * 1.3m depth with total volume of about 6 m3. The bed was constructed using painted galvanized steel to reduce the heat absorption. The bed depth was filled with different types of gravels and soils as following (from bottom to top):

• Bottom layer was filled with gravel size (25 - 40 mm) of 15 cm thick.

• The next upper layer was filled with gravel size (10 - 25 mm) of 15 cm thick.

• The top layer of 10 cm thickness was filled with silty sand (fine sand)

• A free board layer of 70 cm thickness was arranged for accumulating the bio-mass

• The bed was planted using local reed bed (Phragmites australis) at the top layer.

• A perforated PVC pipe was installed above the bottom layer by 15cm to act as a drainage system and collect the infiltrated water. The pipe was connected with a concrete manhole to store the percolated water. The manhole was

arranged with submersed pump and water meter for water withdrawal and measurements as in Figure 3.

Septage Dosing tank (1 m3 capacity)

Dosing over whole surface immediately

free board _ Silly sand \ (fine sand)\ r -

Gravel size s ". (10 -25mmj\ '

(25 - 40 mm) 1 % slop

Figure 3: Septage vertical flow reed bed unit Results and Discussion

The total solids (TS), Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Total Kjeldahl Nitrogen (TKN), Total Phosphorus (TP) and Fecal Coliform (FC) are the parameters used to evaluate the efficiency of the reed bed system in treating the bio-solid. Table 1, shows the average concentrations of these parameters for the applied bio-solid and percolated water from reed bed unit.

Table 1: The average concentrations of the chemical and biological applied bio-solid and percolated water from reed bed

Parameters Input Output

(Bio Solid) (Percolate Water)

COD mg/l 14,200.00 600.00

BOD5 mg/l 7,800.00 250.00

TS mg/l 10,186.00 1,000.00

TKN mg/1 2,926.00 56.00

TP mg/1 1,385.00 9.50

FC /100 ml 3.00 x 104 100.00

The BOD5 and COD concentrations in the percolated water were significantly reduced. The removal percentage of COD and BOD5 were 95.77% and 96.79% respectively. The removals percentage of TKN and TP were 98.10% and 99.31% respectively. The removals percentages of the biological indicator FC were 99.67%. The results showed high efficiency of the system in treating the percolated water. The treatment effectiveness can be associated with the reed plants biological ability to transfer the Oxygen through their leafs, stems and roots, resulting of high biological activities of available microorganisms in rhizo-sphere layer [4].

The bio solid treatment efficiency of the reed bed system was checked in removing the total solids in two scenarios: low and high bio solid loadings. The monthly total solids applied quantities in both low and high loadings were 9.37 kg/m2 and 13.16 kg /m2 respectively.

The average percent of the TS removals were 90% and 71% in the low loading and high loading respectively.

Figure 4 shows the total monthly bio solids applied, accumulated and removed. The results present a positive performance in treating the bio solids. The high biological activities of available microorganisms in rhizo-sphere layer stabilize the accumulated bio-solid in the bed and led to form fertile (black) soil with time. In addition, the preliminary treated percolated water from this reed bed unit (Table 1) connected to the urine (gray water) reed bed for further treatment and reuse.

Total solid (g/m2/ Total solid in Aeeumlated biodegradable month) percolated water stablized Total bio Total Solids (g/m3/month) solid i;1 in2 month)

Low bio-solid Loading 1 High bio-solid Loading

Figure 4: Bio-solid treatment efficiency for reed bed system.

3.2. Grey water/ settled wastewater treatment

A vertical flow (reed bed) was used for achieving up-to-date results. The system was used to treat gray water or (settled wastewater) effluent from septic tank, which was used to trap the bio-solid and some of the suspended solids before flowing to the reed bed.

System Design and Operation

The ' time is the main design criteria for the biological treatment in constructed wetland (reed beds). The general dimension of the used gray water vertical flow (reed bed) constructed wetland is (9*2*1.5 m) of a total volume 27 m3. The bed was designed to serve more than 40 persons with daily wastewater production of more than 4 m3. A detention time of more than 2 days, which offered better treatment opportunity, was achieved. The system enabled the vertical flow of the settled wastewater / grey water influent with settling the bio- mass on the top layer of the bed and as evenly as possible into a gravel layer. In order to prevent surfacing of effluent and bad odors, the inlet pipe covered with relatively larger aggregate of (30 mm- 40 mm) diameter size as well as outlet pipe. Using the relatively larger aggregate allow quick and smooth flow, minimize clogging, and ensure easier root intrusion.

As shown in Figure 5, the bed was lined with plastic sheet made of Poly Ethylene. The bed was filled with different aggregates sizes as following (from bottom to top):

• The thickness of bottom layer was 45 cm and gravel size (30 mm- 40 mm)

• The next layer thickness was 25 cm and gravel size (25 mm - 30 mm)

• The second next layer was silty sand soil of 25 cm thick

• The upper layer was cutoff soil of 55 cm thick

• The top layer was planted with local reed 25 seedlings for each square meter

Figure 5 : Schematic diagram for the gray water vertical flow (reed bed) constructed wetland

The outlet facility was designed and constructed to double benefit of reusing the effluent. The effluent could be managed to be reused in irrigating the backyard farms if available and/or to be reused in recharging the groundwater aquifer. Moreover, the facility was arranged to restore the claimed wastewater for time need and reuse in a storage water tank certain capacity. The groundwater recharging facility was arranged with open bottom end concrete manhole 80 cm diameter. Below the recharging manhole, the local soil was replaced with relatively larger gravel of (30- 40 cm) diameter size or 1 m depth. Larger gravel size was used to make the effluent quickly and smoothly infiltration. The outlet facility is represented in Figure 6.

To R«use In Agriculture'

To Groundwater Recharge

Figure 6: Schematic diagram for the gray water vertical flow (reed bed) constructed wetland

Results and Discussion

The efficiency of the gray water / settled wastewater reed bed system was check by testing the influent and effluent water. The test of the influent and the effluent consisted the chemical and biological related parameter as presented in table (3).

The related chemical and biological parameters was tested in the first 3 months of the system after operation. Such initial results represent good potentials for the treatment efficiency of used system. It is expected that the efficiency will be increased with time as reed plant will grow up and their roots net will be enhanced and increased

to perform better transfer of the Oxygen needed for the biological activities of the available microorganisms in rhizo-sphere layer.

Table 2: The average values of measured chemical and biological parameter

Parameters Influent Effluent Removal

(Gray water / (Reclaimed %

settled water)

wastewater)

BOD5 mg/l 397 122 69.3

COD5 mg/l 683 215 68.5

FC u/100ml ..105 ..103 99.9 (2 logs)

Imhoff (settlable solids) ml/l 0.5 0.08 84

Total Slid (TS) mg/l 1500 1250 19.5

Total Suspended Solids (TSS) mg/l 300 177 41

TKN mg/l 85 50 54.5

The average removals of the measures BOD5 and COD in reed bed unit were about 69% and 68% respectively. The fecal coliform (FC) removal is the biological indicator for the significant efficiency of the reed bed system, which was around 2 logs (99.9%) with a retention time around less than 2 days. While, the normal level of FC removal in Stabilization Bond System with retention time around 20 days reaches 4 logs. This is very significant indicator for the effectiveness of the reed bed treatment system. This level of (FC) removal is suitable for reuse in agricultural activities based on the FAO guidelines.

4. Future Planned Activity

4.1. Human Excreta separation using semi dry toilet

The human excreta and urine separation from source will be managed through using innovative equipment suitable for daily basic sanitation needs called "semi dry toilet". The idea of the semi dry toilet depends upon closing the natural cycle of the nutrients and from food to food cycle, moreover, to reduce the water consumption. The main structure of the semi dry toilet will consist of two main basins. The first basin will be arranged for the urine separation, collection and transformation. The design surface area of the urine basin will be approximately 2/3 the toilet surface area. The basin structure will be designed with reasonable slopes for quick and hygiene release of the urine. The basin at the bottom will be connected to the house level gray water network in order to let the urine transfer and connect to the different sources of gray water

such as washbasins, showers, and kitchen basins, etc. The gray water will be finally connected to the vertical flow (reed bed) constructed wetland for the treatment and reuse. While, the second toilet basin will be designed for the feces separation, collection, and transformation for treatment and reuse. The feces transformation will be through using either special ducts or directly to the anaerobic digestion and aerobic treatment units. The main design criteria for the semi dry toilet will be as following:

• The system efficiency will ensure the minimization of the loss of carbon and nutrients and water.

• The system will be in a reasonable total life cycle cost, including production, installation, maintenance and operation costs.

• The system will be technically and sociologically adapted to the targeted culture.

• The system will be robust enough for the minimal deviation of the system operation.

• The system will be safely and hygienic handle of the human excreta and urine.

4.2. Human Excreta anaerobic biological treatment

The human excreta will be treated anaerobically before the direct apply (aerobic) treatment in order to double the benefit in reusing the excreta in biogas production and fertile soil formation. The human excreta (bio-solid) mixed with little water will be transferred from the semi dry toilet to the anaerobic digestion unit. In the digestion unit, a bacterial decomposition process occurs and stabilizes the organic wastes of the bio-solid; and produces a mixture of methane and carbon dioxide gas (biogas). The biogas will be reused in producing the energy needed for the human. In addition, through the anaerobic digestion, the bad odor of the fresh bio-solid and the possibilities for growth of bleeding insects will be totally reduced and disappeared.

The generated well-stabilized bio-solid from the digestion unit will be transferred to the aerobic treatment in the septage vertical flow (reed bed) constructed wetland. In the wetland, the fertile soil will be formed due to continuous accumulation of the decomposed bio-solids with reasonable time in the free board of the wetland.

5. Conclusions:

Through the study, the conclusion could be summarized in the following points:

• Both bio-solid and gray water/ settled wastewater reed bed constructed wetlands systems indicated a good potential and promising treatment efficiencies. Such

systems could be a suitable solution for wastewater problems in Gaza strip and similar regions.

• In order to avoid the unpleasant smell of the applied biosolid to the reed bed and the growth of bleeding insects, the bio-solid suggested to be applied first to anaerobic digestion to make the bio-solid more stabilized and to generate the biogas.

• The applied system is a cost - effective system for disposal, treatment and reuse of wastewater either in agricultural purposes and / or groundwater aquifer recharge

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