I've been studying harp writing for a while, it's amazing, and difficult.
It sounds nice but in general terms it looks more like a writing for piano. For example: you have not taken advantage of the interval the harpist can play with one hand (tenths are easy), with quick notes it's quite hard to play more than 4 notes in a row, the harpist uses 4 fingers in each hand, never the little one; this is possible if you could use both hands as it happens sometimes in the score (m. 41...). The broad tesitura of the instrument is not represented.
Trills in the harp are, in fact, tremolos and they are notated this way (bisbigliando is also characteristic, but is different):
The major concern is, perhaps, the pedals and enharmonic pitches. The number of pedal changes at a time are limited. I've read that harpist don't like the changes in the score, because most times there's no only one solution. But as a composer, I always write those changes, just for me, to be aware if what I'm writing is possible or not.
I don't know if you know about this issue... In the left side there are three pedals, in the right side four:
Each pedal has three positions (flat, natural, sharp). You can change one pedal of the left side and one pedal of the right side at the same time. For more changes, you have to give time in the score.
Your piece starts as follows:
D C# B
E F# G - A
In measure 13 you have a modulation where the pedals are:
D C Bb
Eb F G Ab...... In fact you don't need to change A to Ab, so let's consider you have to change
C# - C, B - Bb, E-Eb , F# - F
As you can see it's not possible, you have two simultaneous changes in the left side and two more in the right side.
If you are interested in harp writing (which is wonderful), I would suggest:
Reading some book on orchestration
Watching tutorials in youtube (there are many)
Listening and watching scores for harp