The Municipality of Chitungwiza, Zimbabwe

St. Mary’s Sewage Pipeline Rehabilitation

Project

and

on the

Site: The Municipality of Chitungwiza, St. Mary’s Sewage Pipelines

Start Date: October 2010

Duration: Initial treatment process- 8 weeks, maintenance- ongoing.

Coordinators: City Engineers for the Municipality of Chitungwiza

Project Consultants: Dave Kempen and Tim Fennell

Timing of Treatments: During normal working hours.

Population using this Sewage Pipeline: 300,000 to 500,000 people

Volume of wastewater in Sewage Pipelines: 9.6 Mega liters/day.

Length of Sewage Pipeline: 30,000m of pipes. 15,000m were treated.

Average Daily Temperatures: 25 C

Project Overview

The Municipality of Chitungwiza is located south of Harare. It is the third largest municipality and the fastest growing population centre in Zimbabwe. Today’s population count, including a migrant component, are estimated at approximately 2 million inhabitants.

This high density commuter town was formed in 1978 from the amalgamation of three

townships: Seke,

Zengeza and

St. Mary’s. It received

full municipal

status in

1981.

Background Information

Lake Chivero

The Treatment Process

The AZAcomp compound was applied on a daily basis to predetermined manholes on the Sewage Pipeline network. These were sites experiencing higher than average blockage rates.

The treatment process was initiated shortly before the onset of the rainy season which has previously proven to be a very chaotic time for the municipal sewer team.

The sewer lines all converge to flow into Pump Station 1. The lines vary from 100mm (4’’) to 600mm (24’’) in diameter.

Blockages caused by tree roots etc, were removed manually by digging them out.

ST MARY’S AZACOMP APPLICATION

Attn: Town Clerk, Town Engineer

The following is the proposed action programme to clear a portion of St Mary’s blocked sewer pipes using AZAcomp for 8 weeks, every 1000m.

150 mm Pipe. 18 kg– 126 kg total requirement 1 bag a day for first 14 days.1 bag per week for 6 weeks.

200 mm Pipe.40 kg – 72 kg total requirement2 bags day for first 14 days.2 bags weekly for 6 weeks

300 mm Pipe.70 kg – 156 kg total requirement 3 bags for first 14 days.2 to 3 bags per week for 6 weeks

Note: The bags are water-soluble and & each bag contains 1 kg of AZAcomp. Avoid any contact of bag with water/sweat until application.These application rates are intended a guide only.

Treatment ResultsAfter regular AZAcomp treatment for four weeks, all treated pipelines and manholes appeared clear and operating as designed. The foul odour around the manholes was vastly reduced, and surrounding areas experienced a reduction in the fly population.

There were no blockages reported on any of the AZAcomp treated pipelines during heavy rains.

There was a large increase in the volume of sand deposited at Pump Station 1 which is the final outlet.

From Pump Station 1, where no transfer pumps are operational, the effluent has been diverted to the Manyami River, which flows into Lake Chivero.

The effluent water released has changed from a black brackish water with foul odour, to a odour free greenish water which has a degree of visibility.

Project Synopsis

The Municipality of Chitungwiza initiated the St. Mary’s Sewage Pipeline Rehabilitation project to establish AZAcomp’s efficiency in reducing the blockages, and reduced flow capacity in underground sewage pipelines. The majority of blockages were due to an accumulation of sand mixed with biodegradable organic effluent consisting primarily of human excrement, some fats and oils, and other organic waste matter.

The restricted flow in the pipelines resulted in manholes overflowing, and raw sewage flowing freely down residential streets. This problem was getting worse each year. Entire sections have been non-functional some for up to 5 years.

Compounding the pollution issue of raw sewage in the streets for residents of these high density neighborhoods was an overabundance of flies, and foul odour. This problem was exacerbated during the rainy season in previous years.

The objective of this project was to use AZAcomp to liquefy the sludge component of the compacted sand/effluent mass, increasing the porosity of the mixture thereby enabling the sand to be washed away with the increased water flowing through the pipes.

The initial cost for this rehabilitation process was less than US$ 0.10 per person.

The only alternative to this treatment process would have required replacement of the pipelines as high-pressure cleaning of the lines failed to work. A guide for the cost of these pipes alone came to US$ 1.5 million. The whole replacement project would exceed US$ 3 million, and years to complete.

Effluent with floating biomass filling the manhole

Manhole no longer filled with effluent. Shows the hole at the bottom of the culvert and effluent flowing through the pipes below.

Pictorial OverviewAside from the degraded concrete, these manholes are extremely clean. Note the absence of any organic sludge on the walls. Without the presence of organic matter, the foul odour and fly populations at all manholes were greatly reduced.

Effluent flowing into the manhole through one pipe system into the main system.

With improved flow capacity, the manhole is no longer filling up.

Effluent with floating

biomass, almost

completely filling

manhole.

The Chaminuka Manhole is a 300mm (12 ‘’) mainline. This line has been constantly problematic, with continual blockages and overflowing. City engineers believed this line had been incorrectly installed in a positive gradient. They had never witnessed it flowing freely before. However, it is now free flowing.

The Chitungwiza Medical Clinic Manhole was previously completely blocked. It is now clean and virtually empty with the underneath pipeline free flowing. This manhole posed grave potential health risks.

With blockages and flow restrictions no longer an issue, the amount of effluent water reaching Pump Station 1 has increased, and the pipeline system is operating much more efficiently.

The problem of sewer/manhole overflow of raw sewage was so chronic that people had vegetable gardens planted along the edges of the overflow where organic matter had accumulated.

Note the vegetable garden next to the manhole and overflow.

Hmm…wonder what the E.coli and coliform counts here are?

A newly planted vegetable garden making use of raw sewage for ‘flood irrigation’.

The Chitungwiza suburbs of Seke and Zengeza will begin their pipeline rehabilitation projects early in 2011, provided they are able to secure sufficient funds to finance the project.

The below pictures are some examples of what they are, and have been, experiencing.

Project Notes

With the AZAcomp treatment of the sewage pipeline system, the foul odour and fly population problems were so drastically reduced that the city engineers were inundated with phone calls from residents thanking them for fixing the problems.

There were no reported cases of Cholera from the St. Mary’s area this rainy season.

An interesting note, and one with widespread implications. Raw sewage from the populace in the Lake Chivero watershed (approx. 5 million), both urban and rural, flows directly into Lake Chivero. This same lake is where the-so-called “fresh” water supply is drawn for the City of Harare.

A maintenance dosage of AZAcomp is suggested to greatly increase the wastewater outflow quality and to keep the sewer system flowing smoothly.