origin is domestic sewage from the residential and accommodation areas as well as
from offices and kitchen facilities. Based on the population of the settlement, the
design daily flow rate is 350 m
3 /day.
Raw wastewater is collected in a collection tank and lifting station within the
settlement, where after simple screening (coarse screen) it is pumped and sent to the
new CW facility. The facility is located next to the settlement area perimeter fence,
i.e. approx. 150 m away from the first buildings. The CW facility is designed to
generate a final treated effluent that complies with the water quality requirements of
the MD 145/93 Oman Standard A (Table 7.2). It was also a requirement to have a
final disinfection stage of the final effluent so that it does not constitute a biological
aerosol hazard in order to comply with requirements of the MD 145/93 Oman
Standard. The treated effluent will be reused for irrigation of green public areas
within the settlement.
The design of the wetland facility is based on a raw wastewater quality of BOD
400 mg/L, COD 700 mg/L, TSS of 400 mg/L, ammonia nitrogen of 65 mg/l and oil
and grease 20 mg/L. The influent pH range is from 6 to 9. It should also be
mentioned that the proposed technical solution for wastewater treatment should be
odourless, environmentally friendly, easy to install, with minimal chemical dosing,
less space requirements, minimal operation and maintenance cost and sludge-free
operation. This wetland system is designed to meet the irrigation Standard A, Oman
Ministerial Decision 145/93 (Table 7.3; i.e. BOD 5 < 10 mg/L, NH 4 -N < 5 mg/L,
TN < 21 mg/L, TSS < 15 mg/L, NO 3 < 50 mg/L, faecal coliform < 5 CFU/100 mL,
intestinal helminth/nematode eggs < 1 egg/L).
The overall design and concept of the constructed wetland facility is shown in
Fig. 7.1. The CW consists of two stages; the first stage is a vertical flow constructed
wetland (VFCW) and the second stage is an aerated constructed wetland (ACW)
with horizontal subsurface flow. Figure 7.2 shows an aerial overview of the
two-stage constructed wetland facility.
The first stage is a VFCW filter (surface of 2100 m
2 ) and receives raw wastewater
(after coarse screening) (Fig. 7.3). The VFCW surface is separated in three parallel
cells. Each day, only one cell is loaded with the raw wastewater, which is applied at
regular intervals across the surface of the cell through a feeding pipe network, in
order to ensure uniform distribution of the organic solids in the raw wastewater
(Stefanakis et al. 2014). Each bed receives the full organic load and the solid content,
resulting in a decreased total surface area needed. The feeding strategy is the
intermittent loading and comprises feeding (1–2 days) and resting periods
(2–4 days) (Stefanakis and Tsihrintzis 2012). The appropriate duration of the resting
periods allows for aerobic conditions restoration and minimizes the risk of clogging
due to solid retention and the gradual creation of a residual solid layer on top of the
gravel media surface. The operational cycle is controlled by opening or closing three
manual valves located at the front end of the VFCW in a valve chamber.
With this setup, a primary settling tank is avoided and there is no need for
additional management tasks and equipment for sludge handling and dewatering.
The fast introduction of wastewater onto each cell bed surface creates temporary
water ponding of 3–5 cm depth and temporary saturated conditions in the top gravel
200
A. I. Stefanakis
from offices and kitchen facilities. Based on the population of the settlement, the
design daily flow rate is 350 m
3 /day.
Raw wastewater is collected in a collection tank and lifting station within the
settlement, where after simple screening (coarse screen) it is pumped and sent to the
new CW facility. The facility is located next to the settlement area perimeter fence,
i.e. approx. 150 m away from the first buildings. The CW facility is designed to
generate a final treated effluent that complies with the water quality requirements of
the MD 145/93 Oman Standard A (Table 7.2). It was also a requirement to have a
final disinfection stage of the final effluent so that it does not constitute a biological
aerosol hazard in order to comply with requirements of the MD 145/93 Oman
Standard. The treated effluent will be reused for irrigation of green public areas
within the settlement.
The design of the wetland facility is based on a raw wastewater quality of BOD
400 mg/L, COD 700 mg/L, TSS of 400 mg/L, ammonia nitrogen of 65 mg/l and oil
and grease 20 mg/L. The influent pH range is from 6 to 9. It should also be
mentioned that the proposed technical solution for wastewater treatment should be
odourless, environmentally friendly, easy to install, with minimal chemical dosing,
less space requirements, minimal operation and maintenance cost and sludge-free
operation. This wetland system is designed to meet the irrigation Standard A, Oman
Ministerial Decision 145/93 (Table 7.3; i.e. BOD 5 < 10 mg/L, NH 4 -N < 5 mg/L,
TN < 21 mg/L, TSS < 15 mg/L, NO 3 < 50 mg/L, faecal coliform < 5 CFU/100 mL,
intestinal helminth/nematode eggs < 1 egg/L).
The overall design and concept of the constructed wetland facility is shown in
Fig. 7.1. The CW consists of two stages; the first stage is a vertical flow constructed
wetland (VFCW) and the second stage is an aerated constructed wetland (ACW)
with horizontal subsurface flow. Figure 7.2 shows an aerial overview of the
two-stage constructed wetland facility.
The first stage is a VFCW filter (surface of 2100 m
2 ) and receives raw wastewater
(after coarse screening) (Fig. 7.3). The VFCW surface is separated in three parallel
cells. Each day, only one cell is loaded with the raw wastewater, which is applied at
regular intervals across the surface of the cell through a feeding pipe network, in
order to ensure uniform distribution of the organic solids in the raw wastewater
(Stefanakis et al. 2014). Each bed receives the full organic load and the solid content,
resulting in a decreased total surface area needed. The feeding strategy is the
intermittent loading and comprises feeding (1–2 days) and resting periods
(2–4 days) (Stefanakis and Tsihrintzis 2012). The appropriate duration of the resting
periods allows for aerobic conditions restoration and minimizes the risk of clogging
due to solid retention and the gradual creation of a residual solid layer on top of the
gravel media surface. The operational cycle is controlled by opening or closing three
manual valves located at the front end of the VFCW in a valve chamber.
With this setup, a primary settling tank is avoided and there is no need for
additional management tasks and equipment for sludge handling and dewatering.
The fast introduction of wastewater onto each cell bed surface creates temporary
water ponding of 3–5 cm depth and temporary saturated conditions in the top gravel
200
A. I. Stefanakis