the system would comprise - indwe environmental sludge drying beds ... configuration will allow for...
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Prelim design report - August 2013 - Rev 0 2 Rev 0 /August 2013
The system would comprise : o head of works o up-flow anaerobic sludge blanket reactor o primary aerobic pond o four secondary aerobic ponds o aquatic pond o anaerobic digestion pond o sludge drying beds
At this meeting it was suggested that a pump station be constructed on the site currently occupied by the package plant, and it was recommended that an inlet works be constructed ahead of the pump station, to condition the sewage before it is pumped to the proposed pond system. At the conclusion of the meeting it was decided that potential pond sites would be investigated using Google Earth and topographical maps, followed by a site visit. Land issues pertaining to the proposed sites were to be investigated including matters such as ownership, zoning, alignment with the municipalitys Spatial Development Plan, as well as the existence of any potential land claims. A report covering the potential pond sites was submitted in June 2013. The following report deals with the preliminary design of the pond system and includes a summary of the operational procedures and estimated operational costs.
Prelim design report - August 2013 - Rev 0 3 Rev 0 /August 2013
2 SITE LOCATION AND DESCRIPTION
2.1 Geographical Location
Ngqushwa Municipality, comprising 14 wards, is situated within the Amathole District Municipality and is an amalgamation of the districts of Peddie, Hamburg and a portion of the King Williams Town district. In the sub-regional context, Ngqushwa Municipality is situated in the western portion of the Amathole District Municipality area. It is made up of two urban centres (Peddie and Hamburg) and 120 rural villages. Peddie falls in Ward 11. Peddie is the Municipal seat and is located along the King Williams Town and Grahamstown N2 road. It is 53 km from King Williams Town and 68 km from Grahamstown.
Peddie lies on the boundary between the coastal zone and the coastal plateau zone. The climate can be summarised as cool subtropical with warm summers and cool winters. Average annual rainfall is 500 mm distributed predominantly during the summer months between October and June, but rainfall is erratic. The average monthly temperature and rainfall figures for Bathurst ( 50 km south-west of Peddie) are presented in Table 2.1 below. Table 2.1: Average Monthly Climatic Data measured at Bathurst (1993 2002)
Month Average Maximum Temperature (0C)
Average Minimum Temperature (0C)
January 26.2 17.4 71.82
February 27.1 17.9 39.88
March 26.0 17.1 85.77
April 24.2 15.1 53.89
May 22.9 13.1 22.92
June 21.7 11.2 28.19
July 21.2 10.5 41.71
August 21.4 11.1 51.53
September 21.9 12.0 58.66
October 22.5 13.3 61.09
November 23.8 14.6 74.79
December 25.3 16.4 87.12
Prelim design report - August 2013 - Rev 0 4 Rev 0 /August 2013
3 EXISTING INFRASTRUCTURE
3.1 Existing Sanitation Services
A description of the existing waterborne and on-site sanitation services and, where applicable, their serviceability and sufficiency, is discussed in the Sanitation Master Plan Report compiled by Arcus GIBB (May 2005).
3.2 Existing Levels of Sanitation Service
A summary of the existing levels of sanitation service in Peddie is shown in Table 3.1 below.
Table 3.1: Summary of Existing Sanitation Services for Peddie
Area Number of developed erven
Type of Sanitation Level of Service
Peddie Town 288 Waterborne (1) Above RDP standards
Peddie Extension A 550 VIP latrines Equal to RDP standards
Peddie Extension B 1420 Waterborne Above RDP standards
Durban Village 156 VIP latrines Equal to RDP standard
Septic tanks Above RDP standard
Ordinary pit latrines Below RDP standard
German Village 2 Ordinary pit latrines Below RDP standards
(1) Only approximately 40% of developed erven are actually connected to the sewers at this stage
3.3 Existing Wastewater Treatment Works (WWTW)
An extended aeration sewage treatment plant was constructed in Peddie in 1997. The works is located in the public open space on the eastern side of the N2 next to the Ngqushwa River. The works was designed for a hydraulic capacity of 250 k/day and a BOD capacity of 125 kg/day. Currently the works is overloaded and the effluent is not complying with the General Limits as set out by Section 21 of the National Water Act.
Prelim design report - August 2013 - Rev 0 5 Rev 0 /August 2013
4 POPULATION AND ESTIMATED HYDRAULIC AND BIOLOGICAL LOADING
Table 4.1 is a summary of the population and their contribution to the WWTW as set out in the Peddie Sanitation Master Plan, Arcus GIBB, March 2005.
Table 4.1: Population Growth, Hydraulic and Biological Loading to Proposed WWTW
contributing to WWTW flows
Present situation 1033 73 53 142
Future situation (for immediate
9693 673 503 1112
Proposed WWTW 12186 1000 650 1134 The proposed WWTW will cater for population
growth up to 2015
Future situation (for ultimate
18537 1833 1023 2079 The proposed WWTW will cater for population
growth up to 2032
Year Population Assumed growth rate per year = 2.50%
Prelim design report - August 2013 - Rev 0 6 Rev 0 /August 2013
By 2015 2016 the population is projected to increase to approximately 12 105 people which will generate a total flow to the proposed works of 1 000 k/day. To provide capacity in the WWTW pond system for the next 20 years, a 2 000 k/day plant is proposed, which will cater for flows beyond the year 2035.
Prelim design report - August 2013 - Rev 0 7 Rev 0 /August 2013
5 PROPOSED INFRASTRUCTURE
In planning the proposed scheme, GIBB adopted the population and flow estimates from the Sanitation Master Plan Report, March 2005. These figures correlate with the guidelines set out by the Red Book (Guidelines for the Provision of Engineering Services and Amenities in Residential Township Development).
5.2 Wastewater Treatment Unit Process
The proposed wastewater treatment process is a combination between an Up-flow Anaerobic Sludge Blanket Reactor, a Facultative-Aerobic Pond System and a Floating Aquatic Pond. The proposed WWTW has a capacity of 2 000 k/day ADWF and an average daily organic load of 2 268 kg COD/day. The WWTW is designed to treat domestic sewage. The proposed WWTW consists of the following unit process components: Primary Treatment
a) Inlet works (including screening, de-gritting and inflow measurement) b) Up-flow anaerobic sludge blanket reactor (2x)
a) Primary facultative pond (1x) b) Secondary facultative pond (1x) c) Tertiary facultative pond (3x)
a) Floating aquatic pond (1x) b) Disinfection of the final effluent
a) Anaerobic sludge reactor b) Sludge drying beds
Prelim design report - August 2013 - Rev 0 8 Rev 0 /August 2013
5.2.1 Primary Treatment
(a) Inlet Works Duty/standby, dual, coarse and fine hand raked screens will be installed in the inlet works. Three horizontal grit channels will allow for gravity grit settling and manual grit removal. Provision will be made to store and remove screenings and grit by means of waste bins and an accompanying trailer. Open channel venturi flume measurement will ensure continuous flow measurement. The flow metering records will allow for proper planning of future upgrades. The works is sized based on the existing and future domestic sewage loads from the local community. The design hydraulic capacity of the inlet works is 2000 kl/day ADWF (4000 kl/day PDWF and 6000 kl/day PWWF). The works will therefore have sufficient capacity for any foreseeable future WWTW upgrade in terms of capacity. Design flow velocity through the inlet works will be between 0.6 to 1.0 m/s for average to peak flow conditions. The grit channels will be designed for flow through velocities of between 0.3 to 0.4 m/s.
(b) Up-flow Anaerobic Sludge Blanket Reactor (UASBR) A dual configuration UASBR will be constructed to reduce major organic COD loads, in order to minimise pond surface area. The UASBR will also initiate anaerobic sludge digestion, which can reduce anaerobic sludge reactor size. The screened/degritted sewage will enter the UASBR at the bottom and flow to the top through the anaerobic sludge blanket. The overflow will proceed to the secondary treatment. The dual configuration will allow for flexibility during reactor maintenance and sludge withdrawal periods. The reactors will have three sludge withdrawal points, at different levels, to allow the operator to optimally determine sludge blanket level. Sludge withdrawn from the bottom of the UASBR will be introduced hydraulically into the bottom of the Anaerobic Sludge Reactor (ASR). General tech