Estimation of Waste Load Malou San Diego-McGlone Marine Science Institute University of the Philippines

Coastal Water Body PrecipitationEvaporation Residual flux Mixing flux Runoff Groundwater Sewage/Waste

Sources of Waste (human activity) household activities livestock agriculture urban runoff aquaculture manufacturing

Steps in the Calculation of Waste Load 1. Identify relevant human activities households - solid waste, domestic sewage, detergent livestock - piggery, poultry, cattle agriculture - soil erosion, fertilizer runoff urban runoff - unsewered areas aquaculture - prawns, fish manufacturing - food, textiles, chemicals

2. Determine the level of each human activity from government statistics, preferably at local level household - size of the population livestock - no of pig, chicken, cow aquaculture - tons of prawn, fish urban runoff - urban area agriculture - tons of soil eroded

3. Approximate TN and TP (in effluent discharge) TN = activity level x discharge coefficient TP = activity level x discharge coefficient T

The discharge coefficients for various human activities are given in the following spreadsheet. This spreadsheet calculates TN and TP load in waste generated by various human activities. Knowledge of the activities relevant to the coastal area is necessary and the only input needed in the spreadsheet would be the level of the waste generating activity (fill in white cells).

Sources of Discharge Coefficients

TN and TP (in the spreadsheet) are approximated using the following calculations.

TN = activity level x discharge coefficient Ex. for Domestic Sewage activity level = 2000 persons discharge coefficient = 4 kgN/person/yr TN = 4 kgN/person/yr x 2000 persons TN = 8000 kgN/yr TP = activity level x discharge coefficient discharge coefficient = 1 kgP/person/yr TP = 1 kgP/person/yr x 2000 persons TP = 2000 kgP/yr

If only BOD and COD data are available, TN and TP can be approximated using the following ratios* TN/BOD = 0.5 TP/BOD = COD/BOD = 2.6 Ex if available data is BOD at 5 mg/L TN = 5 mg/L x 0.5 = 2.5 mg/L Ex if available data is COD at 5 mg/L TN = 5 mg/L x 1/26 (BOD/COD) x 0.5 = 1 mg/L

The previous spreadsheet also approximates DIN and DIP. The following calculations illustrate how this is done.

4. Calculate DIN and DIP in the effluent discharge Assumption: 25% of waste enter the bay Use stoichiometric ratio* DIN/TN = 0.38 DIP/TP =0.5 DIN = TN÷atomic wt N x DIN/TN x 25% DIN = 8000 kgN/yr ÷14 g/mole x 0.38 x 0.25 DIN = 54,000 moles/yr DIP = TP÷atomic wt P x DIP/TP x 25% DIP = 2000 kgP/yr÷31 g/mole x 0.5 x 0.25 DIP = 8,000moles/yr

The following N and P budgets of a Philippine bay (LINGAYEN GULF) are given to illustrate how waste is quantified and show that this is an important input to the system.

NITROGEN AND PHOSPHORUS BUDGETS FOR LINGAYEN GULF

Lingayen Gulf Manila Bay South China Sea

Lingayen Gulf divided into three boxes Upper Gulf 1764 km 2, 81 km 3 Bolinao 126 km 2, 0.3 km 3 Nearshore 210 km 2, 3.2 km 3

LINGAYEN GULF Water Budget (fluxes in 10 9 m 3 /yr) Upper Gulf 1764 km 2, 81 km 3 Nearshore 210 km 2, 3.2 km 3 Bolinao 126 km 2, 0.3 km 3 Ocean V R = 1 V R = 8 V R = 11 V Q = 0.2 V G = 0.7 V P = 0.3 V P =4 V Q = 2 V G = 0.4 V Q = 8 V G = 0.2 V P = 0.5 V E = 0.3 V E = 0.4 V E = 4

S 2 = 34.0 S 1N = 31 S 1B = 33.5 LINGAYEN GULF Salt Budget (salt fluxes in 10 9 psu-m3/yr) Upper Gulf 1764 km 2, 81 km 3 Nearshore 210 km 2, 3.2 km 3 Bolinao 126 km 2, 0.3 km 3 Ocean V X = 68 V R S R = 34 S 3 = 34.4 V R S R = 376 V X = 940 V R S R = 260V X = 87  = 2 days  = 27 days  = 12 days

Table 1. Effluents produced by economic activities in Lingayen Gulf (in 10 6 mole yr -1 ).

V O DIP O = 35 V O DIP O = 46 Nearshore LINGAYEN GULF DIP Budget (fluxes in 10 6 moles/yr) Upper Gulf Bolinao Ocean DIP 1B = 0.4 DIP 2 = 0.1µM DIP 1N = 0.4µM V X DIP X = 20 V R DIP R = 2 V R DIP R = 0 V X DIP X = 26 DIP 3 = 0.0µM V R DIP R = 1 V X DIP X = 94 V Q DIP Q = 1 V Q DIP Q = 88 V Q DIP Q = 1 V G DIP G = 1 V G DIP G = 2 V G DIP G = 0  DIP=-27  DIP = +10  DIP = -97

V O DIN O = 262 V O DIN O = 350 DIN 1N = 1.7µM V Q DIN Q = 4 V Q DIN Q = 8 V Q DIN Q =128 Ocean LINGAYEN GULF DIN Budget (fluxes in 10 6 moles/yr) Upper Gulf Nearshore Bolinao DIN 1B = 3.9µM DIN 2 = 0.8µM V X DIN X = 211 V R DIN R = 10 V R DIN R = 2 V X DIN X = 78 DIN 3 = 0.5µM V R DIN R = 7 V X DIN X = 282 V G DIN G = 28 V G DIN G =11 V G DIN G = 39  DIN = -180  DIN = -310  DIN = -313

Stoichiometric Links Net ecosystem metabolism (p-r) or photosynthesis minus respiration, can be calculated using the formulation (p-r ) = -  DIP  (C:P) part Estimates of (nfix-denit) or N-fixation minus denitrification, can be approximated using the formulation (nfix-denit) =  DIN -  DIP  (N:P) part where (C:P) part and (N:P) part are the ratios of organic matter reacting in the system

Table 2. Summary of nonconservative fluxes in three boxes of Lingayen Gulf. +5.9

Table 3. Effects of changing waste load on (p-r) and (nfix-denit).

IMPLICATIONS  The system is able to breakdown waste inputs and export most of these as N and P out of the Gulf with some amount retained, perhaps in the sediments.  Since the average nutrient concentrations of N and P in the upper Gulf have not varied much over the years, this is an indication of the system’s current assimilative capacity.  However, buildup of organic matter is critical for the nearshore and Bolinao boxes and will eventually affect the Gulf’s ability to process these materials.

 Malou:  LOICZ web pages: