| Abstract: | The national water company, Male Water and Sanitation Company Pvt Ltd intends to upgrade the water production setup at Male’ to cater for the increase of demand and usage of water in the capital island. Under the upgrading project additional desalination plants are proposed along with additional deep wells for attaining feed water. Along with the additional desalination plants and boreholes, two addition brine outlets are proposed. Therefore this report is prepared to fulfill the environmental clearances necessary under the EIA regulation before commencement of setting up of brine discharge lines.
The proposed project involves laying of two brine discharge pipes west of existing brine discharge pipe at Vaidheri magu. The new proposed pipes are installed as part of the proposed upgrading of water production by MWSC.
Water consumption in Male’ has increased along with the increase of population; in this regard demand for water is at a steady raising trend. According to MWSC current capacity of the company will not be sufficient for the near future and at the moment is operating just under maximum production capacity. Therefore the company requires upgrading its water production system and capacity. At present 8 RO systems with capacity of 13,500m3/day is operated by the company.
Two 400mm PE pipes will be used as brine outlet pipe. The pipes will be laid adjacent to one and other. The holes drilled at the quay wall will be sealed using Rheomac ® 707 type chemical cement.
Since the project involves laying pipes, a mini excavator will be used for trenching works, before commencement of work, permit will be attained from Male’ Municipality Office for closing the work area (closing roads). The quay wall will be drilled using industrial concrete drill (electrical) to cut two holes adjacent to one and other. After cutting the holes pipe will be laid protruding in to basin. The drilled holes will be sealed after installation of pipe using water proofing chemical sealant Rheomac ® 707 type chemical cement. The length of the pipe line is 370m initiating from the MWSC plot run long the Vaidheri magu and across Boduthakurfaanu magu.
Although two pipes are installed for the time being only one pipe will be used as brine discharge while the other one is for future use. At the current increase rate of demand it is anticipated that production has to be increase in the near future again, therefore two pipes are installed.
The rate of flow of brine is approximately 6000m3/day. The immediate salinity of brine discharge from RO plant is 51.4 ppt, while test done at the outlet area (basin) is 36.3 ppt. The existing brine outlet has rate of flow of 21,000m3/day for existing 8 RO plants. The proposed brine outlet is designed for a rate of flow of 24,00m3/day, envisaging future expansion and increase of water production capacity. Although two pipes are installed under the proposed project, one pipe will be used under the proposed upgrading project.
Wave condition at the project site is dictated by wind waves and swells waves at the channel in between North and South Male atoll. The southern side harbor is developed just at the edge of the reef flat area. The area receives swell waves throughout the year, while wind waves are predominantly affected during SW monsoon. The southern side is observed sea wall constructed with Tetrapods. 130m sections are laid with a 30m gap. These gaps are partially closed with low Tetrapod line to reduce transmittance of swell waves.
Since the project involves brine discharge to the basin, basin area was assessed for live coral growth. The quay wall area was devoid of live coral, while near the seawall few Pocillopora colonies were observed. Overall similar to most basins live coral was scarce, while fish life was mostly juvenile Pomacentrids and Tetraodontids.
Impacts on the environment from various activities of the proposed project (constructional impacts) and operation impacts have been identified through interviews with the project management team, field data collection surveys and based on past experience in similar development projects.
Since the project involves only laying of pipeline, only social impacts are envisaged in terms of construction impacts. The road area during installation process has to be closed, while basin area will also be closed (only near quay wall area). Since the construction works will only take two weeks extent of impacts (social) will be minor.
In regard to impact due to drilling works, only minor impact is envisaged. During drilling works dust and fine debris may be released in to the water column at the basin area. This impact is envisaged to be minor.
Although the brine solution contains natural ingredients of the seawater it may cause damage by its unnatural concentration to marine population near the outlet. The other concern is the chemicals from pre treatments and from membrane periodical cleaning can harm the habitat. One example is the use of biocides such as chlorine, which is used to clean pipes or to pre-treat the water. These chemicals must be treated before they are released to the ocean. It has to be noted that no live coral is observed at the quay wall area near the discharge point.
Since the scope of report is limited to installation of brine discharge outlet, alternatives are given for location of outlet.
The proposed location was chosen, in terms of shortest distance to MWSC plot and distance from existing brine discharge outlet. The distance from existing discharge outlet and proposed outlet is approximately 200m. Alternative for brine discharge is deep well discharge. Considering these two options, deep well discharge will be costly and needs to be drilled deeper than the existing deep well feed water boreholes. Installation one deep well may not be sufficient to pump brine at the existing flow rate. Therefore considering both options, brine discharge at basin is thought to be feasible in terms impacts and cost.
Based on the water test done by MWSC and in-situ testing, rapid dilution of salinity, temperature, pH and chemicals to near ambient levels were recorded in the near field (1-2m) from the outlet.
Therefore, with due consideration to the environmental components identified above and the extent of the project activities and their likely and predicted impacts identified the consultant concludes that the project components and designs are feasible and appropriate mitigation measures have been considered to correct and minimize any unfavorable environmental changes. |
