1. sampling:
- the data was directly taken from routine quality monitoring checks by rnml's environment section at the basamuk refinery.
- samples were collected at intervals of 4 times per day or 24-hourly basis and analyzed accordingly.
- sampling bottles, beakers, and other equipment were prepared and cleaned using distilled water following standard operating procedures (sops).
- samples were collected at the mixing tank, the point of tailing discharge, using a metal sampler.
- sampling gloves were worn to ensure quality.
- a total of four tailing samples were taken at 6-hour intervals for a daily (24-hour) sampling period.
- the results for the 31 days of august 2013 were used in this study.
2. laboratory analysis:
- the samples were brought to the laboratory for further processing.
- the collected samples were filtered using a 0.45μm diameter filter paper, and the ph measurements were obtained.
- the ph meters were calibrated with standard buffer solution and distilled water before analyzing each new sample.
- the discharge flow velocity was recorded from special software installed monitoring computers, using the formula: discharge velocity (m³/h) = volume (m³) / time (h).
- the tailing content in the sampling bottles was acidified with 10-20 ml of concentrated nitric acid (hno₃) to preserve and maintain the solubility of dissolved metals.
- the samples were analyzed directly for heavy metals concentration using inductively coupled plasma - mass spectrometry (icp-ms).
the main points from the given information are:
1. metals are classified into two groups: (a) other metals and (b) toxic heavy metals, based on their definitions, toxicity characteristics, and environment permit standard concentrations (epsc).
2. other metals have an epsc value above "one," while toxic heavy metals have values below "one."
3. metals such as cd, pb, se, zn, cu, as, ag, hg, and cr are common constituents in mine tailing wastes and are proven to be toxic to the environment and organisms, including humans.
4. the monthly average concentrations of the metals (mn, zn, ni, co, and cu) in the tailing pore water are below their respective epsc values, indicating that they do not pose an immediate threat to the local benthic environment.
5. the monthly average concentrations of the toxic heavy metals (cd, pb, se, as, ag, hg, and cr) in the tailing effluent are all less than 0.01 mg/l, suggesting that they are ecologically safe to be disposed of and will have a negligible immediate impact on the marine ecosystem.
6. the concentrations of the metals in the tailing water conform to the compliance values stipulated in the environmental permit (ep) issued by the government of papua new guinea.
the main points from the given information are:
1. discharge velocity of tailing:
- discharge velocity is a vital component of the dstp (deep-sea tailing placement) system.
- it is important to maintain a consistent flow to support the density current and minimize plume shearing or dispersal of tailing materials.
- the recommended range of daily average flow discharge velocity is 800 - 2500 m³/h.
- the investigated values were between 1677 - 2075 m³/h, with a monthly average of 1270 m³/h, indicating compliance with the permitted velocities.
- however, there were significant fluctuations in the discharge velocities between days 3-8 and 21-27, which can potentially promote critical conditions at the discharge terminal and cause density current issues.
2. acidity (ph) of tailing effluent:
- the ph analysis is important to determine the acidity or alkalinity of the tailing effluents prior to discharge.
- the refinery uses high pressure acid leaching (hpal) technology, and counter-current decantation and addition of limestone/lime are used for neutralization.
- the recommended ph range in the environmental permit (ep) is a minimum of 6.5 and a maximum of 9.0 units.
- the daily ph values of the tailing water fluctuated between 8.12 and 8.55, with an average of 8.12, indicating that the tailing waste was adequately neutralized to alkaline levels.
- the ph values of the discharge are similar to that of seawater, blending in well with the natural seawater environment.
briefly put the above information in brief in one paragraph